Astronomy Picture of the Day |
APOD: 2009 March 10 - Horsehead and Orion Nebulae
Explanation:
Adrift 1,500 light-years away in one of
the night sky's
most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
They appear in opposite corners of this
stunning mosaic taken with a digital camera attached to a small telescope.
The magnificent emission region, the
Orion Nebula (aka M42), lies at the upper right of the picture.
Immediately to its left is a prominent bluish
reflection nebula sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow at the lower left.
Alnitak is the easternmost star in
Orion's belt and is seen as the
brightest star to the left of the
Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Pervasive tendrils
of glowing hydrogen gas are easily
traced
throughout the region in
this deep field image of the same region.
APOD: 2009 February 24 - Barnard's Loop around the Horsehead Nebula
Explanation:
Why is the
Horsehead Nebula surrounded by a bubble?
Although hard to make out, the famous
Horsehead Nebula is the slight
dark indentation in the bright streak
just to the left of the image center.
Glowing like an
emission nebula, the origin of the
bubble, known as
Barnard's Loop, is currently unknown.
Progenitor hypotheses include the
winds
from bright Orion stars and the
supernovas
of stars long gone.
Barnard's Loop is too faint to be
identified with the unaided eye.
The nebula
was discovered only in 1895 by
E. E. Barnard on long duration film exposures.
The above image was taken in a single
specific color
emitted by
hydrogen to
bring out detail.
To the left of the
Horsehead Nebula,
visible as a small dark indentation, is the photogenic
Flame Nebula.
APOD: 2009 February 22 - Orion Nebula: The Hubble View
Explanation:
Few cosmic vistas excite the imagination like
the Orion Nebula.
Also known as
M42,
the nebula's glowing gas surrounds hot young stars at the edge of an
immense interstellar
molecular cloud only 1,500 light-years away.
The Orion Nebula offers one of the best opportunities
to study how stars are born partly because it is the nearest large
star-forming region,
but also because the nebula's
energetic stars have
blown away
obscuring gas and dust clouds that would otherwise block
our view - providing an intimate look at a
range of ongoing stages
of
starbirth and evolution.
This detailed image of the
Orion Nebula is the sharpest ever, constructed using data from the
Hubble Space Telescope's
Advanced Camera for Surveys and the European Southern Observatory's
La Silla 2.2 meter telescope.
The mosaic
contains a billion pixels at full resolution
and reveals about 3,000 stars.
APOD: 2009 February 16 - The Great Carina Nebula
Explanation:
A jewel of the southern sky,
the Great
Carina Nebula, aka NGC 3372, spans over 300 light-years,
one of our Galaxy's largest star
forming regions.
Like the smaller, more northerly
Great Orion Nebula, the
Carina Nebula is easily visible to the
unaided eye, though at a distance of 7,500
light-years
it is some 5 times farther away.
This
stunning telescopic view from the
2.2-meter ESO/MPG telescope La Silla Observatory
in Chile reveals remarkable details of the region's glowing filaments of
interstellar gas and
dark cosmic dust clouds.
The Carina Nebula is home to young, extremely massive stars, including
the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun.
Eta Carinae
is the bright star left of the central dark notch in
this field and near the dusty Keyhole
Nebula (NGC 3324).
APOD: 2009 February 11 - Orion s Belt Continued
Explanation:
Yesterday's skyscape featured
Alnitak, Alnilam, and Mintaka,
the stars of
Orion's Belt.
Today's also presents the easternmost belt star, Alnitak, at the
bottom right of the field, surrounded by the well-known
Horsehead
and Flame nebulae.
But this view sweeps
farther to the east (left) and north (top)
detailing subtler cosmic clouds of gas and dust scattered through
the fertile, nebula rich region.
The scene is anchored at the top left by the eerie
blue glow
and ominous dark dust lanes of
reflection
nebula M78.
Like the Horsehead, the Flame, and the
Orion Nebula itself,
M78 is a readily visible part of the large
Orion
Molecular Cloud complex some 1,500 light-years distant.
APOD: 2009 February 10 - Orion s Belt
Explanation:
Alnitak,
Alnilam,
and
Mintaka,
are the bright bluish stars
from east to west (left to right) along the diagonal in
this gorgeous cosmic vista.
Otherwise known as the
Belt of Orion, these
three blue supergiant stars are hotter and much more
massive than the Sun.
They lie about 1,500 light-years away, born
of Orion's
well-studied interstellar clouds.
In fact, clouds of gas and dust adrift in
this region have
intriguing and some surprisingly familiar shapes, including the
dark Horsehead
Nebula and Flame Nebula near
Alnitak at the lower
left.
The famous Orion Nebula
itself lies off the bottom of this
star field
that covers about 4.5x3.5 degrees on the sky.
This
image was taken last month with a digital camera attached to a small
telescope in
Switzerland,
and better matches
human color
perception
than a more detailed composite taken over 15
years ago.
APOD: 2009 February 5 - NGC 604: X-rays from a Giant Stellar Nursery
Explanation:
Some 3 million light-years distant in nearby spiral
galaxy M33,
giant stellar nursery
NGC 604 is
about 1,300 light-years across,
or nearly 100 times the size of the
Orion Nebula.
In fact, among the star forming regions within the Local Group of
galaxies, NGC 604 is second in size only to 30 Doradus,
also known as
the Tarantula Nebula in the
Large Magellanic Cloud.
This space-age
color composite of X-ray data (in blue hues)
from the Chandra Observatory, and
Hubble optical data
shows that NGC 604's cavernous bubbles and cavities are filled with a
hot, tenuous,
X-ray
emitting gas.
Intriguingly, NGC 604 itself is divided by
a wall of relatively cool gas.
On the western (right) side of the nebula,
measurements
indicate that material is likely
heated to X-ray temperatures by the energetic winds
from a cluster of about 200 young, massive stars.
On the eastern side the X-ray filled cavities seem to be older,
suggesting
supernova explosions from the end of
massive star evolution contribute to their formation.
APOD: 2008 December 16 - Orion Dawn Over Mount Nemrut
Explanation:
What's that in front of Orion?
Forty kilometers north of
Kahta,
Turkey,
lies
Mount Nemrut, a mountain adorned with the fragments of vast statues built over 2000 years ago.
The
stone sculptures
once stood nearly 10 meters high and depicted lions,
eagles,
various ancient
gods, and
King Antiochus I Theos, who ruled
Commagene
from 86 BC to 38 BC.
Ruins of the bodies of several sitting
figures are visible on the hill above, illuminated by
moonlight.
Zeus'
head can be found near the above image's center,
while the king's head is seen next closest to the horizon.
Visible far in the distance in
this image, taken three months ago, is the familiar
constellation of Orion.
The red patch just below
Orion's belt is the
Orion Nebula,
while the bright star to the left of Orion is
Sirius.
On the far left, a red and brightening horizon announces that the Sun is beginning to rise.
APOD: 2008 November 26 - The Horsehead Nebula in Orion
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a
photographic plate in the late 1800s.
The red glow originates from
hydrogen
gas predominantly behind the nebula, ionized by the nearby bright star
Sigma Orionis.
A blue
reflection nebula dubbed
NGC 2023 surrounds the bright star at the lower left.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the process of forming.
Light takes about 1500 years to reach us from the
Horsehead Nebula.
The above image
was taken earlier this month with a 0.6-meter telescope at the
Mt. Lemmon SkyCenter in
Arizona,
USA.
APOD: 2008 November 11 - The Cosmic Web of the Tarantula Nebula
Explanation:
First
cataloged as a star, 30 Doradus is actually an
immense star forming region in nearby galaxy
The Large Magellanic Cloud.
The region's spidery appearance is responsible for its popular name,
the Tarantula
nebula, except that this tarantula is about 1,000
light-years across, and 180,000 light-years
away in the southern constellation
Dorado.
If the Tarantula
nebula were at the distance of the
Orion Nebula
(1,500 light-years), the nearest stellar nursery to Earth, it
would appear to cover about 30 degrees (60
full moons)
on the sky.
The spindly arms of the
Tarantula nebula
surround
NGC 2070,
a star cluster that contains some of the brightest,
most massive stars known.
Intriguing details of the nebula are visible in
this
scientifically-colored image.
The cosmic Tarantula
also lies near the site of the closest
recent supernova.
APOD: 2008 November 7 - Cygnus Trio
Explanation:
In this colorful mosaic, filaments of gas and dust span
some 9 degrees across central Cygnus, a
nebula rich constellation
along the northern
Milky Way.
A trio of nebulae with popular names highlights
the beautiful skyscape -
the Butterfly, the Crescent, and the Tulip.
At left, the Butterfly Nebula
(IC 1318), lies near bright star Gamma Cygni.
The Butterfly's expansive, glowing, wing-shaped gas clouds are
divided by a dark dust lane.
Near center, the Crescent Nebula
(NGC 6888) is more compact,
a cosmic bubble with a bright edge blown by winds from a massive
Wolf-Rayet star.
On the right is the Tulip Nebula
(Sh2-101), a small
emission region shaped like a blossoming flower viewed from
the side.
All are within a few thousand light-years of the Sun in the
Orion
spiral arm of our galaxy.
The gorgeous mosaic is presented in
false color,
constructed from image data recorded through narrow band filters.
The range of colors was created by a mapping of
emission from hydrogen, sulfur and oxygen atoms in the nebula
to red, green, and blue hues.
APOD: 2008 October 31 - A Witch by Starlight
Explanation:
By starlight this eerie visage shines in the dark,
a crooked profile evoking its popular name, the
Witch Head Nebula.
In fact, this entrancing
telescopic
portrait gives the impression
the witch has fixed her gaze on Orion's bright supergiant
star Rigel.
Spanning over 50 light-years, the dusty cosmic cloud strongly
reflects nearby Rigel's blue light, giving it the characteristic color
of a reflection nebula.
Cataloged as IC 2118, the Witch Head Nebula
is about 1,000 light-years away.
Of course, you might see a witch this
scary tonight,
but don't panic.
Have a safe and
Happy Halloween!
APOD: 2008 October 23 - Great Orion Nebulae
Explanation:
The Great Nebula
in Orion, also known as M42, is one of the
most famous nebulae in the sky.
The star forming region's glowing gas clouds and hot young stars
are on the right in this sharp and colorful
two frame mosaic
that includes the smaller
nebula M43
near center and dusty, bluish reflection nebulae
NGC 1977 and friends on the left.
Located at the edge of an otherwise invisible giant molecular
cloud complex,
these eye-catching nebulae represent only a small
fraction of this galactic neighborhood's wealth of
interstellar material.
Within the well-studied stellar nursery, astronomers have also
identified what appear to be numerous
infant solar systems.
The gorgeous skyscape spans nearly two degrees or about 45 light-years
at the Orion Nebula's estimated distance of 1,500 light-years.
APOD: 2008 October 15 - Camera Orion
Explanation:
Orion, the Hunter, is one of the most easily recognizable
constellations
in planet Earth's night sky.
But Orion's stars and
nebulas don't look
quite as colorful to the eye as they do in
this lovely camera image, taken
early last month at the
Black Forest Star Party from
Cherry Springs State Park in
Pennsylvania,
USA.
In this single exposure, cool red giant
Betelgeuse
takes on a yellowish tint as the brightest star at the far left.
Otherwise Orion's hot blue stars are numerous, with
supergiant Rigel balancing Betelgeuse at the upper right, Bellatrix at the upper left, and
Saiph at the lower right.
Lined up in Orion's belt (bottom to top) are
Alnitak, Alnilam, and Mintaka
all about 1,500
light-years away, born of the constellation's well studied
interstellar
clouds.
And if the middle "star" of
Orion's sword
looks reddish and fuzzy to you, it should.
It's the stellar nursery known as the
Great Nebula of Orion.
APOD: 2008 April 9 - A Large Magellanic Cloud Deep Field
Explanation:
Is this a spiral galaxy?
No. Actually, it is the
Large Magellanic Cloud (LMC), the largest
satellite galaxy of our own
Milky Way Galaxy.
The LMC is
classified as a
dwarf irregular galaxy because of its normally chaotic appearance.
In this deep and wide exposure, however, the full extent of the
LMC becomes visible.
Surprisingly, during longer exposures, the
LMC begins to resemble a
barred spiral galaxy.
The
Large Magellanic Cloud lies only about 180,000
light-years
distant towards the constellation of
Dorado.
Spanning about 15,000 light-years, the LMC was the site of
SN1987A,
the brightest and closest
supernova
in modern times.
Together with the
Small Magellanic Cloud (SMC), the LMC can
be seen in Earth's southern hemisphere with the unaided eye.
APOD: 2008 April 8 - Southern Orion: From Belt to Witch
Explanation:
Do you recognize the belt of Orion in this image?
The familiar trio of stars,
visible to the unaided eye,
can be found across the upper left.
Otherwise, the southern part of the constellation Orion has taken
on a new look in
this unusually deep and wide view
First note that the lower left belt star,
Alnitak,
is the easternmost star in Orion's belt.
Left of Alnitak is the Flame Nebula,
with clouds of bright emission and dramatic dark dust lanes.
Directly below
Alnitak,
a close inspection will reveal the
Horsehead Nebula.
Farther right and below is the Orion Nebula,
M42,
itself visible to the unaided eye.
The brightest star in the frame, near the bottom right, is
Rigel.
A bright blue star, Rigel illuminates the ominously shaped dust patch known as the
Witch Head Nebula, visible as the
blue reflection nebula near the
lower right corner.
Finally, appearing as a vast red ring and encompassing the entire region, is
Barnard's Loop.
Humans
could see this entire menagerie, unaided, were their eyes
about 10,000 times more sensitive.
APOD: 2008 April 6 - Wisps Surrounding the Horsehead Nebula
Explanation:
The famous Horsehead Nebula in Orion is not alone.
A deep exposure shows that the
dark familiar shaped indentation,
visible just below center, is part of a
vast complex of absorbing
dust and
glowing gas.
To bring out details of the
Horsehead's pasture, amateur astronomers at the
Star Shadow Remote Observatory in
New Mexico,
USA
fixed a
small telescope on the region for over seven hours filtering out all but a
very specific color of
red light emitted by
hydrogen.
They then added the image to a full color frame taken over three hours.
The resulting
spectacular picture details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by
stellar winds and
ancient supernovas.
The Horsehead Nebula lies 1,500
light years
distant towards the
constellation of
Orion.
Two stars from the Orion's Belt
can be found in the
above image.
APOD: 2008 April 3 - South of Orion
Explanation:
This tantalizing array of nebulae and stars can be found
about 2 degrees south of the famous
star-forming Orion Nebula.
The
region abounds with energetic young stars producing jets and
outflows that push through the surrounding
material at speeds of hundreds of kilometers per second.
The interaction creates luminous shock
waves known as
Herbig-Haro (HH) objects.
For example, the graceful, flowing arc just right of center
is cataloged as HH 222, also called the Waterfall Nebula.
Seen below the Waterfall, HH 401 has a distinctive cone shape.
The bright bluish nebula below and left of center
is NGC 1999, a dusty cloud reflecting
light from an embedded variable star.
The entire cosmic vista
spans over 30 light-years, near the edge of the
Orion
molecular cloud
complex
some 1,500 light-years distant.
APOD: 2008 March 18 - M78 and Reflecting Dust Clouds in Orion
Explanation:
An eerie blue glow and ominous columns of dark dust highlight M78 and other bright
reflection nebula
in the constellation of Orion.
The dark filamentary
dust not only absorbs light, but also reflects the
light of several bright blue stars that
formed recently in the nebula.
Of the two reflection nebulas pictured above, the more famous nebula is M78, on the upper right, while NGC 2071 can be seen to its lower left.
The same type of scattering that colors the
daytime sky further enhances the blue color.
M78
is about five
light-years across and visible through a small telescope.
M78 appears
above only as it was 1600 years ago, however, because that is how long it takes light to go from
there to here.
M78
belongs to the larger
Orion Molecular Cloud Complex
that contains the
Great Nebula in Orion and the
Horsehead Nebula.
APOD: 2008 March 7 - Comet over California
Explanation:
Still gracing northern skies, a fading Comet Holmes lies at the top
edge of this
colorful
skyview, recorded on March 4.
The reddish emission nebula below it is NGC 1499, also known as
the California Nebula
for its resemblance to the outline of the state
on the US west coast.
Of course, the two cosmic clouds by chance lie along nearly the same
line-of-sight and so only appear to be close together and of similar
size.
The California Nebula is actually about 100 light-years long and 1,500
light-years away, drifting through the Orion Arm of our spiral Milky Way
Galaxy.
Comet Holmes is about 20
light-seconds in diameter, sweeping
through our solar system a mere 25
light-minutes away,
beyond the orbit of Mars.
The molecules of the comet's gaseous
coma
fluoresce in sunlight.
The California Nebula's glow is characteristic of hydrogen atoms
recombining with
long lost electrons, originally
stripped away
(ionized) by ultraviolet starlight.
Providing the energetic starlight is Xi
Persei,
the prominent star below the nebula.
APOD: 2008 February 21 - Orion's Horsehead Nebula
Explanation:
The Horsehead
Nebula is one of the most famous nebulae on the sky.
It is visible as the dark indentation to the red
emission nebula seen just below
and left of center in the
this photograph.
The brightest star on the left is located in the belt of the familiar
constellation Orion.
The horse-head
feature is dark because it is really an opaque
dust cloud that lies in
front of the bright red
emission nebula.
Like clouds in
Earth's atmosphere, this cosmic cloud has
assumed a
recognizable
shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance.
The emission nebula's red color is caused by
electrons recombining
with
protons
to form
hydrogen atoms.
Also visible in the picture are blue
reflection nebulae that
preferentially reflect the blue light from
nearby stars.
APOD: 2007 December 25 - Mars and Orion Over Monument Valley
Explanation:
Welcome to
The World At Night.
Sharing the night sky seen around the world, this view from
Monument Valley,
USA includes a picturesque foreground of famous buttes.
Buttes
are composed of hard rock left behind after
water eroded away the surrounding soft rock.
The two buttes on the image left are known as the
Mittens,
while Merrick Butte is on the right.
Recorded just last week,
planet Mars is at the left of the skyscape,
a glowing beacon of orange that is the brightest object in the frame.
To the right of Mars lies the
constellation of Orion.
Betelgeuse is the reddish star near
the center and the Belt of Orion
and the Orion Nebula
are farther right.
Finally, the bright blue star
Rigel
appears above Merrick Butte in this stunning view of
The World At Night.
APOD: 2007 December 21 - Horizon to Horizon
Explanation:
Scroll right and journey from horizon to horizon as your gaze sweeps
through
the zenith in
the night
sky over Beg-Meil, France.
Recorded on December 13th,
the entertaining panorama
(image key)
covers 210 degrees
in 21 separate exposures, beginning on the beach with bright star
Sirius rising in the southeast.
Look up (pan right) to encounter the nebula rich constellation
of Orion and
continue on to find the lovely Pleiades
star cluster.
Farther along, higher in the sky, is the famous
Comet Holmes,
still
gracing the northern hemisphere's night with its
remarkable expanding coma.
Finally, just before diving into the
urban glow from city lights along
the northwestern horizon (far right), check out the
double star cluster in
Perseus and take in the cosmic streak of a bright
Geminid
Meteor.
APOD: 2007 December 20 - Reflections on the 1970s
Explanation:
The
1970s are sometimes ignored by astronomers.
In particular, this beautiful grouping of reflection nebulae
in Orion - NGC 1977, NGC 1975, and NGC 1973 - are
usually overlooked in favor of the substantial glow from the
nearby stellar nursery better known as the
Orion Nebula.
Found along Orion's sword just north
of the
bright Orion Nebula complex, these reflection nebulae are
also associated with
Orion's giant molecular cloud about
1,500 light-years away, but
are dominated by the characteristic blue color of interstellar
dust reflecting
light from hot young stars.
North is down in
this sharp color telescopic image
from New South Wales,
Australia,
so the more familiar Orion Nebula borders the top
of the view.
NGC 1977 stretches across the field just above center,
separated from NGC 1973 (below left) and NGC 1975 (below right)
by darker regions of obscuring dust.
Many northern hemisphere observers claim to see the general shape of
a running man
in the cosmic dust cloud but, of course, they're looking at the view
upside down.
APOD: 2007 November 16 - Rocket Fuel
Explanation:
This gorgeous
image of Orion shows off the constellation's
young stars and cosmic clouds of hydrogen gas and dust.
Made with a film camera tracking the stars on November 11,
the exposure lasted some 40 minutes.
It includes the Great Orion Nebula
(near center),
a string of well-known nebulae leading upwards
to Orion's three belt stars,
and the large semi-circular arc known as
Barnard's Loop that seems
to end at the bottom right,
next to bluish supergiant star Rigel.
Serendipitously, the picture also recorded a bright, comet-shaped cloud
not known to share the sky with
Orion's famous stars and nebulae.
Also spotted
by other skywatchers, the mystery cloud was quickly
recognized as a fuel dump from a booster
rocket used
to place a satellite in
geosynchronous orbit.
Reflecting sunlight, the fuel dump plume begins on the west (right)
side of the star field
and expands as it slowly drifts eastward and fades
during the time exposure, creating the
wedge-shaped streak.
APOD: 2007 October 27 - The Great Carina Nebula
Explanation:
A jewel of the southern sky,
the Great
Carina Nebula, aka NGC 3372, spans over 300 light-years,
one of our galaxy's largest star
forming regions.
Like the smaller, more northerly
Orion Nebula, the Carina Nebula
is easily visible to the naked eye, though at a distance of
7,500 light-years it is some 5 times farther away.
This
stunning telescopic view reveals remarkable details of the
region's glowing filaments of interstellar gas and dark
cosmic dust clouds.
The Carina Nebula is home to young, extremely massive stars, including
the still enigmatic variable
Eta
Carinae, a star with well over 100 times the mass of the Sun.
Eta Carinae
is the bright star left of the central dark notch
in this field and just below the dusty Keyhole
Nebula (NGC 3324).
APOD: 2007 October 6 - X-Ray Stars of Orion
Explanation:
The stars of Orion shine brightly
in visible light in planet Earth's night sky.
The
constellation harbors the closest large stellar nursery,
the Great Nebula of Orion,
a mere 1,500 light-years away.
In fact, the apparently bright clump of stars near the center
of this false color Chandra
x-ray telescope picture
are the massive stars of
the Trapezium - the
young star cluster which powers much of the nebula's
visible-light glow.
The stars shown
in blue and orange are young sun-like stars; prodigious sources
of x-rays thought to be produced in hot
stellar coronae and
surface flares in a young star's strong
magnetic field.
Our middle-aged
Sun itself was
probably thousands of times
brighter in x-rays when, like
the
Trapezium stars, it was
only a few million years old.
The
x-ray image
spans about 2.5 light-years
across the central region of the Orion Nebula.
APOD: 2007 August 22 - Tentacles of the Tarantula Nebula
Explanation:
The largest, most violent star forming region known in the whole
Local Group of galaxies
lies in our neighboring galaxy the
Large Magellanic Cloud (LMC).
Were the Tarantula Nebula at the distance of the
Orion Nebula -- a local star forming region --
it would take up fully half the sky.
Also called
30 Doradus, the red and pink
gas indicates a massive
emission nebula, although
supernova remnants and
dark nebula also exist there.
The bright knot of stars left of center is called
R136 and contains many of the most
massive, hottest, and brightest stars known.
The
above image taken with the
European Southern Observatory's (ESO's)
Wide Field Imager
is one of the
most detailed ever of this vast star forming region.
ESO has made it possible to fly around and into this detailed image by
clicking here.
APOD: 2007 May 27 - The Horsehead Nebula
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a
photographic plate in the late 1800s.
The red glow originates from
hydrogen
gas predominantly behind the nebula, ionized by the nearby bright star
Sigma Orionis.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the process of forming.
Light takes about 1500 years to reach us from the
Horsehead Nebula.
The
above image was taken with the
0.9-meter telescope at
Kitt Peak National Observatory.
APOD: 2007 May 11 - LDN 1622: Dark Nebula in Orion
Explanation:
The silhouette of an intriguing
dark nebula
inhabits this cosmic scene, based on images from the
Palomar
Observatory Sky Survey.
Lynds' Dark Nebula
(LDN) 1622 appears against a faint background
of glowing hydrogen gas only easily seen in long telescopic
exposures of the region.
LDN 1622 lies near the plane of our Milky Way Galaxy,
close on the sky to
Barnard's
Loop - a large cloud surrounding the rich
complex of emission nebulae found
in the Belt and Sword
of Orion.
But the obscuring dust of LDN 1622 is thought to be much closer
than Orion's more famous nebulae, perhaps only 500 light-years away.
At that distance, this 1 degree wide field of view
would span less than 10 light-years.
APOD: 2007 March 26 - Bullet Pillars in Orion
Explanation:
Why are bullets of gas shooting out of the Orion Nebula?
Nobody is yet sure.
First discovered in 1983, each bullet is actually about the size of
our Solar System, and
moving at about 400 km/sec from a central source dubbed IRc2.
The age of the bullets, which can be found from their speed and distance from
IRc2, is very young -- typically less than 1,000 years.
As the
bullets rip through the interior of the
Orion Nebula,
a small percentage of iron gas causes the tip of each bullet to glow blue,
while each bullet leaves a tubular pillar that glows by the light of heated hydrogen gas.
Pictured above, the Orion bullets were captured in unprecedented detail by the adaptive optics technology of the Gemini North telescope.
M42, the Orion Nebula,
is the closest major star forming region to us and filled with changing
dust, gas, and bright stars.
The Orion Nebula, is located about 1,500
light years away and
can be seen with the unaided eye toward the
constellation of Orion.
APOD: 2007 February 2 - Flame Nebula Close-Up
Explanation:
Of course, the Flame Nebula is not on fire.
Also known as
NGC 2024,
the nebula's suggestive
reddish color is due to the glow
of hydrogen
atoms at the edge of the giant Orion
molecular cloud complex some 1,500 light-years away.
The hydrogen atoms have been
ionized, or stripped of their
electrons, and glow as the atoms and electrons recombine.
But what ionizes the
hydrogen atoms?
In this
close-up view,
a dark lane of absorbing interstellar dust stands out
in silhouette against the
hydrogen glow
and actually hides
the true source of the Flame Nebula's energy from optical
telescopes.
Behind the dark lane lies a cluster of hot, young stars, seen
at infrared
wavelengths through the obscuring dust.
A young, massive star in that cluster is
the likely source
of energetic ultraviolet radiation that ionizes the
hydrogen gas in the Flame Nebula.
APOD: 2007 January 25 - Orion's Cradle
Explanation:
Cradled in glowing hydrogen,
stellar
nurseries in Orion
lie at
the edge of a giant molecular cloud some 1,500 light-years away.
This breath-taking view
spans about 13 degrees across
the center of the well-known constellation with the
Great Orion
Nebula, the closest large star forming region,
just right of center.
The deep mosaic
also
includes (left of center), the Horsehead
Nebula, the Flame Nebula, and Orion's belt stars.
Image data acquired with a
hydrogen alpha filter adds
other remarkable features to this wide angle
cosmic vista -- pervasive tendrils of energized
atomic hydrogen gas and portions of the surrounding
Barnard's Loop.
While the Orion Nebula and belt stars are easy to see with the
unaided eye, emission from the extensive interstellar
gas is faint and much harder to record, even in telescopic views of the
nebula-rich complex.
APOD: 2007 January 6 - The Orion Deep Field
Explanation:
Adrift 1,500 light-years away in one of
the night sky's most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
But even fainter filaments of glowing gas are easily traced
throughout the region in
this
stunning composite image
that includes exposures filtered to record emission
from hydrogen atoms.
The view reveals extensive
nebulosities associated with
the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
A magnificent emission region, the
Orion
Nebula (aka M42) lies at the
upper right of the picture.
Immediately to its left are a cluster of prominent bluish
reflection nebulae sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow left of center.
Alnitak is the easternmost star in Orion's belt and
the brightest star to the left of the Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Completing the trio of Orion's belt
stars, bluish Alnilam and Mintaka form a line with Alnitak,
extending to the upper left.
APOD: 2006 December 29 - Alnitak, Alnilam, Mintaka
Explanation:
Alnitak,
Alnilam,
and
Mintaka,
are the bright bluish stars
from east to west (left to right) along the diagonal in
this gorgeous cosmic vista.
Otherwise known as the
Belt of Orion, these
three blue supergiant stars are hotter and much more
massive than the Sun.
They lie about 1,500 light-years away, born
of Orion's
well-studied interstellar clouds.
In fact, clouds of gas and dust adrift in this region have
intriguing and some surprisingly familiar shapes, including the
dark Horsehead
Nebula and Flame Nebula near
Alnitak at the lower left.
The famous Orion Nebula
itself lies off the bottom of
this star field that covers an impressive 4.4x3.5
degrees on the sky.
The color picture was composited from
digitized
black and white photographic plates recorded
through red and blue astronomical filters, with a computer synthesized
green channel.
The plates were taken using the
Samuel
Oschin Telescope, a wide-field survey instrument at
Palomar
Observatory, between 1987 and 1991.
APOD: 2006 December 16 - A Path To Orion
Explanation:
Last Saturday, the
Space
Shuttle Discovery lit up the night
as it climbed into orbit
above planet Earth.
From Oak Hill, Florida, USA - about 30 miles north
of the Kennedy Space Center - design engineer
Andrew Arigema tracked the shuttle and recorded a four minute
time exposure of the exhaust plume
along Discovery's path against the background of the starry sky.
At the upper left, the end of the drifting plume is
punctuated by
Alnitak, Alnilam, and Mintaka in a vertical line, the belt
stars of Orion.
To the right of the belt stars, the pinkish jewel
in Orion's sword is not a star at all, but the great
Orion Nebula.
Still farther to the right, at the foot of the hunter, lies Rigel,
the brightest star in view.
Rigel is
a hot supergiant star some 700 light-years in the distance.
APOD: 2006 December 11 - IC 2118: The Witch Head Nebula
Explanation:
Double, double toil and trouble;
Fire burn, and cauldron bubble -- maybe
Macbeth should have consulted the Witch Head Nebula.
This suggestively shaped
reflection nebula
is associated with the
bright star Rigel in the
constellation Orion.
More formally known as
IC 2118,
the Witch Head Nebula glows primarily by light reflected from bright
star Rigel, located just
off the upper right edge of the
full image.
Fine dust
in the nebula reflects the light.
The blue color is caused not only by
Rigel's blue color but because the
dust grains reflect blue light more efficiently than red.
The same
physical process causes
Earth's daytime sky to appear blue, although the scatterers in
Earth's atmosphere are molecules of
nitrogen and
oxygen.
The nebula lies about 1000 light-years away.
APOD: 2006 December 8 - NGC 2174: Emission Nebula in Orion
Explanation:
A lesser known sight in the
nebula-rich constellation Orion,
NGC 2174
can be found with binoculars near the head of the
celestial hunter.
About 6,400 light-years distant, the glowing cosmic cloud surrounds
loose clusters of young stars.
Covering an area larger than the full Moon on the sky,
this stunning
narrow band image adopts a typical color mapping of
the atomic emission from NGC 2174.
The false-color mapping
shows otherwise red hydrogen emission in green
hues and emphasizes sulfur emission in red and oxygen in blue.
Placing your cursor on the image will reveal an alternative image
of the nebula made through broad band
filters.
The broad band image combines filters in a
closer analogy
to human vision, dominated by the
red glow of hydrogen.
APOD: 2006 November 30 - A Pelican in the Swan
Explanation:
The Pelican Nebula lies about 2,000 light-years
away in the high flying constellation
Cygnus, the Swan.
Also known as IC 5070,
this cosmic pelican is appropriately found
just off the "east coast" of
the North America Nebula
(NGC 7000), another surprisingly familiar looking
emission nebula in Cygnus.
The Pelican
and North America nebulae are part of the
same large and
complex star forming region, almost as nearby as the
better-known Orion Nebula.
From our vantage point,
dark dust clouds (upper left) help define
the Pelican's eye and long bill, while a
bright front of ionized gas
suggests the curved shape of the head and neck.
Based on digitized black and white images from the
Samuel
Oschin Telescope at Palomar Observatory,
this striking
synthesized color view includes two bright foreground
stars and spans about 30 light-years at the estimated distance
of the Pelican Nebula.
APOD: 2006 November 20 - M42: Wisps of the Orion Nebula
Explanation:
The Great Nebula in Orion, an immense, nearby
starbirth region,
is probably the most famous of all
astronomical nebulas.
Here, glowing gas surrounds hot young stars at the edge of an
immense interstellar
molecular cloud only 1500
light-years away.
In the above deep image, faint wisps and sheets of
dust and gas are particularly evident.
The Great Nebula in Orion can be found with the
unaided eye just below and to the left of the
easily identifiable
belt of three stars in the popular constellation Orion.
In addition to housing a bright
open cluster of stars known as the
Trapezium, the
Orion Nebula contains many
stellar nurseries.
These nurseries contain
hydrogen gas, hot young stars,
proplyds, and
stellar jets
spewing material at high speeds.
Also known as
M42, the
Orion Nebula spans about 40 light years and is located in the same
spiral arm of
our Galaxy as the
Sun.
APOD: 2006 October 15 - An Orion Deep Field
Explanation:
Adrift 1,500 light-years away in one of
the night sky's
most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
They both appear in this stunning composite digital image
assembled from over 20 hours of data that includes exposures
filtered to record emission from hydrogen
atoms.
The view reveals extensive
nebulosities associated with
the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
The magnificent emission region, the
Orion
Nebula (aka M42), lies at the
upper right of the picture.
Immediately to its left are a cluster of
of prominent bluish
reflection nebulae sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow at the lower left.
Alnitak is the easternmost star in Orion's belt and
is seen as the brightest star to the left of the Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Fainter tendrils of glowing hydrogen gas are easily traced
throughout the region in
this
Orion deep field.
APOD: 2006 October 10 - Reflection Nebulas in Orion
Explanation:
In the vast
Orion Molecular Cloud complex,
several bright blue nebulas are particularly apparent.
Pictured above are two of the most prominent
reflection nebulas -
dust clouds lit by the
reflecting light of bright embedded stars.
The more famous nebula is
M78,
near the image center, cataloged over 200 years ago.
On the upper left is the lesser known
NGC 2071.
The image was taken with the
Mayall 4-meter telescope
on Kitt Peak,
Arizona,
USA.
Astronomers continue to
study these
reflection nebulas to better understand how interior stars form.
The Orion complex
lies about 1500 light-years distant, contains the
Orion and
Horsehead nebulas,
and covers much of the
constellation of Orion.
APOD: 2006 September 24 - NGC 1499: The California Nebula
Explanation:
What's California doing in space?
Drifting through the Orion Arm of the spiral Milky Way Galaxy,
this cosmic cloud
by chance echoes the outline of
California
on the west coast of the
United States.
Our own Sun also lies within the Milky Way's
Orion
Arm, only about 1,500 light-years from the
California Nebula.
Also known as NGC 1499, the classic emission nebula is around 100
light-years long.
It glows with the red light characteristic of hydrogen atoms
recombining with
long
lost electrons, stripped away (ionized)
by energetic starlight.
In this case, the star most likely providing the energetic
starlight is the bright, hot, bluish Xi Persei,
just right of the nebula and above picture center.
Fittingly, this
composite picture was made with images from a telescope
in California - the 48-inch (1.2-meter)
Samuel
Oschin Telescope - taken as a part of the second National Geographic
Palomar Observatory
Sky Survey.
APOD: 2006 August 18 - Spitzer's Orion
Explanation:
Few cosmic vistas excite the imagination like
the Orion Nebula,
an immense stellar nursery some 1,500 light-years away.
Also known as M42, the nebula is
visible to the unaided eye,
but this
stunning infrared view from the
Spitzer Space
Telescope
penetrates the turbulent cosmic gas and
dust clouds to
explore
the region in unprecedented detail.
At full resolution, the remarkable image data yields
a census of new stars and potential solar systems.
About 2,300 young stars surrounded by
planet-forming disks
were detected based on the
infrared glow of their warm dust,
along with about 200 stellar
embryos,
stars too young to have developed disks.
This 0.8 by 1.4 degree false-color image is
about 20 light-years wide at the distance of the
Orion
Nebula.
APOD: 2006 August 8 - Horse Head Shaped Reflection Nebula IC 4592
Explanation:
Do you see the horse's head?
What you are seeing is not the famous
Horsehead nebula toward Orion but
rather a fainter nebula that only takes on a familiar form with deeper imaging.
The main part of the
above imaged
molecular cloud complex is a
reflection nebula
cataloged as
IC 4592.
Reflection nebulas are actually made up of very fine
dust that normally appears dark but can
look quite blue when reflecting the light of energetic nearby stars.
In this case, the source of much of the reflected light is a star at the eye of the horse.
That star is part of
Nu Scorpii,
one of the brighter star systems toward the
constellation of Scorpius.
A second
reflection nebula
dubbed IC 4601 is visible surrounding two stars on the far right.
APOD: 2006 April 17 - Barnard's Loop around the Horsehead Nebula
Explanation:
Why is the
Horsehead Nebula surrounded by a bubble?
Although glowing like an
emission nebula,
the origin of the
bubble, known as
Barnard's Loop, is currently unknown.
Progenitor hypotheses include the
winds
from bright Orion stars and the
supernovas
of stars long gone.
Barnard's Loop is too faint to be identified with the unaided eye.
The nebula
was discovered only in 1895 by
E. E. Barnard on long duration film exposures.
The above image was taken in a single
specific color emitted by
hydrogen to bring out detail.
To the left of the
Horsehead Nebula,
visible as the small dark indentation
near the image top, is the photogenic
Flame Nebula.
APOD: 2006 March 16 - Eta and Keyhole in the Carina Nebula
Explanation:
South is toward the top in
this
colorful close-up view of the
Great
Carina Nebula (NGC 3372), famous star-forming region of the southern sky.
Covering an area surrounding the
dusty Keyhole
Nebula (NGC 3324) near picture center,
the image spans about 40 light-years within the larger
Carina
Nebula at an estimated distance of 7,500 light-years.
Like the more northerly Orion Nebula, the bright
Carina
Nebula is easily visible to the naked-eye.
But the dramatic colors in this telescopic
picture are mapped colors,
based on three exposures through narrow filters each
intended to record the light emitted by specific atoms in
the gaseous nebula.
Sulfur is shown in blue, hydrogen in green and oxygen in red hues.
The Carina Nebula is home to
young, extremely massive stars, including the still
enigmatic variable
Eta
Carinae, a star with well over 100 times the mass of
the Sun.
Highlighted by diffraction spikes,
Eta is just above
and right (east) of the Keyhole.
APOD: 2006 February 21 - Wisps Surrounding the Horsehead Nebula
Explanation:
The famous Horsehead Nebula in Orion is not alone.
A deep exposure shows that the
dark familiar shaped indentation,
visible just below center, is part of a
vast complex of absorbing
dust and
glowing gas.
To bring out details of the
Horsehead's pasture, amateur astronomers at the
Star Shadow Remote Observatory in
New Mexico,
USA
fixed a
small telescope on the region for over seven hours filtering out all but a
very specific color of
red light emitted by
hydrogen.
They then added the image to a full color frame taken over three hours.
The resulting
spectacular picture details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by
stellar winds and
ancient supernovas.
The Horsehead Nebula lies 1,500
light years
distant towards the
constellation of
Orion.
Two stars from the Orion's Belt
can be found in the
above image.
APOD: 2006 January 30 - NGC 1999: South of Orion
Explanation:
South
of the large star-forming region known as the
Orion Nebula, lies bright blue reflection nebula
NGC 1999.
The nebula is marked with a dark inverted T-shape at the
lower left in a
broad
cosmic vista that spans over 10 light-years.
The dark shape is a dense gas and dust cloud, or
Bok globule,
seen in silhouette against the bright nebula, and likely
a site of future star formation.
At the edge of the
Orion molecular
cloud complex some 1,500 light-years distant, NGC 1999's
illumination is provided by the
embedded variable star V380 Orionis.
The
region abounds with energetic young stars
producing jets and outflows that create luminous shock waves,
including HH (Herbig-Haro) 1 and 2 just below and left of NGC 1999, and
the apparent cascade
of reddish arcs and bow shocks beginning at the upper right.
The stellar jets and
outflows push through the surrounding
material at speeds of hundreds of kilometers per second.
APOD: 2006 January 20 - LL Ori and the Orion Nebula
Explanation:
This esthetic close-up
of cosmic clouds and stellar winds
features LL Orionis, interacting with the
Orion Nebula flow.
Adrift in Orion's
stellar nursery
and still in its formative years,
variable star LL Orionis produces a wind more
energetic than
the wind from our own
middle-aged Sun.
As the fast stellar wind runs into slow moving gas a shock front is
formed, analogous to the
bow
wave of a boat moving through water or
a plane traveling at supersonic speed.
The small, arcing, graceful structure just above and left of
center is LL Ori's cosmic
bow shock, measuring about half a light-year across.
The slower gas is flowing away from the Orion Nebula's hot central star
cluster, the Trapezium, located off the upper left corner
of the picture.
In three
dimensions, LL Ori's wrap-around shock front is shaped like a
bowl that appears brightest when viewed along the "bottom" edge.
The beautiful picture is part of a
large mosaic view of
the complex
stellar nursery in Orion, filled with a myriad of
fluid
shapes associated with
star formation.
APOD: 2006 January 19 - Orion Nebula, The Hubble View
Explanation:
Few cosmic vistas excite the imagination like
the Orion Nebula.
Also known as
M42,
the nebula's glowing gas surrounds hot young stars at the edge of an
immense interstellar molecular cloud only 1,500 light-years away.
The Orion Nebula offers one of the best opportunities
to study how stars are born partly because it is the nearest large
star-forming region, but also because the nebula's
energetic stars have
blown away
obscuring gas and dust clouds that
would otherwise block
our view - providing an intimate look at a
range of ongoing stages
of
starbirth and evolution.
This detailed image of the
Orion Nebula is the sharpest ever, constructed using data from
the Hubble Space Telescope's Advanced Camera for Surveys
and the European Southern Observatory's
La Silla 2.2 meter telescope.
The mosaic
contains a billion pixels at full resolution
and reveals about 3,000 stars.
In apparent size, the picture is as large as the Full Moon.
At the distance of M42 it spans thirteen light-years.
APOD: 2006 January 6 - The Tarantula Nebula
Explanation:
First
cataloged as a star, 30 Doradus is actually an
immense star forming region in nearby galaxy
The Large Magellanic Cloud.
The region's spidery appearance is responsible for its popular name,
the Tarantula
Nebula, except that this tarantula is about
1,000 light-years across, and 180,000 light-years away in
the southern constellation
Dorado.
If the Tarantual Nebula were at the distance of the
Orion Nebula
(1,500 light-years), the nearest stellar nursery to Earth, it
would appear to cover about 30 degrees
on the sky or 60 full moons.
The spindly arms of the
Tarantula Nebula surround
NGC 2070, a cluster
that contains some of the intrinsically brightest,
most massive stars known.
Intriguing details of the nebula's core can be seen in
this
remarkable skyscape, a composite
of 31 hours of exposure time.
This cosmic Tarantula
also lies near the site of the closest
recent supernova.
APOD: 2005 December 27 - IC 2118: The Witch Head Nebula
Explanation:
Double, double toil and trouble;
Fire burn, and cauldron bubble -- maybe
Macbeth should have consulted the Witch Head Nebula.
This suggestively shaped
reflection nebula
is associated with the
bright star Rigel in the
constellation Orion.
More formally known as
IC 2118,
the Witch Head Nebula glows primarily by light reflected from
Rigel, located just outside the top right corner of the
above image.
Fine dust
in the nebula reflects the light.
The blue color is caused not only by
Rigel's blue color but because the
dust grains reflect blue light more efficiently than red.
The same
physical process causes
Earth's daytime sky to appear blue,
although the scatterers in
Earth's atmosphere are molecules of
nitrogen and
oxygen.
The nebula lies about 1000 light-years away.
APOD: 2005 November 30 - Reflections on the Horsehead Nebula
Explanation:
Sculpted by stellar winds and radiation,
a magnificent interstellar dust cloud by
chance has assumed this recognizable shape.
Fittingly named the
Horsehead
Nebula, it is some 1,500 light-years distant,
embedded in the vast Orion
cloud complex.
About five light-years "tall", the dark cloud is cataloged as
Barnard 33
and is visible only because its obscuring dust is
silhouetted against the glowing red
emission
nebula IC 434.
Contrasting blue reflection
nebula NGC 2023 is visible on the lower left.
In this gorgeous color
image, both Horsehead and NGC 2023 seem to be caught in beams
of light shining from above -- but
the beams are actually just internal reflections
from bright star
Sigma
Orionis, just off the upper edge
of the view.
APOD: 2005 November 4 - M78: Stardust and Starlight
Explanation:
Interstellar
dust clouds and bright nebulae abound in the fertile
constellation of Orion.
One of the
brightest,
M78, is just below center in
this sharp widefield view,
covering an area north of
Orion's belt.
At a distance of about 1,500 light-years, the
bluish nebula itself
is about 5 light-years across.
Its blue tint is due to dust
preferentially
reflecting the blue light
of hot, young stars in the region.
Dark dust lanes and other nebulae can easily be traced
through this gorgeous skyscape that
also
includes the remarkable
McNeil's Nebula -- a newly
recognized nebula
associated with
the formation of a sun-like star.
APOD: 2005 October 13 - Alnitak, Alnilam, Mintaka
Explanation:
Alnitak,
Alnilam, and
Mintaka,
are the bright bluish stars
from east to west (left to right) along the diagonal in
this gorgeous cosmic vista.
Otherwise known as the
Belt of Orion, these
three blue supergiant stars are hotter and much more
massive than the Sun.
They lie about 1,500 light-years away, born
of Orion's
well-studied interstellar clouds.
In fact, clouds of gas and dust adrift in this region have
intriguing and some surprisingly familiar shapes, including the
dark Horsehead
Nebula and Flame Nebula near
Alnitak at the lower left.
The famous Orion Nebula
itself lies off the bottom of
this star field that covers an impressive 4.4x3.5
degrees on the sky.
The color picture was composited from
digitized
black and white photographic plates recorded
through red and blue astronomical filters, with a computer synthesized
green channel.
The plates were taken using the
Samuel
Oschin Telescope,
a wide-field survey instrument at
Palomar Observatory,
between 1987 and 1991.
APOD: 2005 September 18 - M42: Wisps of the Orion Nebula
Explanation:
The Great Nebula in Orion, an immense, nearby
starbirth region,
is probably the most famous of all
astronomical nebulas.
Here, glowing gas surrounds hot young stars at the edge of an
immense interstellar
molecular cloud only 1500
light-years away.
In the above deep image, faint wisps and sheets of
dust and gas are particularly evident.
The Great Nebula in Orion can be found with the
unaided eye just below and to the left of the
easily identifiable
belt of three stars in the popular constellation
Orion.
In addition to housing a bright
open cluster of stars known as the
Trapezium, the
Orion Nebula contains many
stellar nurseries.
These nurseries contain
hydrogen gas, hot young stars,
proplyds, and
stellar jets
spewing material at high speeds.
Also known as
M42, the
Orion Nebula spans about 40 light years and is located in the same
spiral arm of
our Galaxy as the
Sun.
APOD: 2005 July 10 - In the Center of the Trapezium
Explanation:
Start with the constellation of Orion.
Near Orion's belt is a fuzzy area known as the
Great Nebula of Orion or
M42.
In this nebula is a bright
star cluster known as the
Trapezium, shown above.
New stellar systems are forming there in gigantic globs of gas and
dust known as Proplyds.
Looking closely at the
above picture also reveals
that gas and dust surrounding some of the
dimmer stars
appears to form structures that point away from the
brighter stars.
The above false color image was made by combining
several exposures from the orbiting
Hubble Space
Telescope.
APOD: 2005 May 19 - X Ray Stars in the Orion Nebula
Explanation:
When our
middle-aged Sun
was just a few
million years old it was
thousands of times brighter
in
x-rays.
In fact, it was likely similar to some of the stars found
in this false-color x-ray composite of the Orion Nebula region
from the Chandra Observatory.
The image is
centered
on bright stars of the nebula's
Trapezium star cluster, and while
analyzing the
Chandra data
astronomers have now found examples of young,
sun-like stars producing intense
x-ray flares.
It sounds dangerous, but the situation may actually
favor the formation of
hospitable
planetary systems like our own.
Energetic flares can produce turbulence in the
planet-forming disks
surrounding the stars -
preventing rocky earth-like planets from spiraling uncomfortably
close to and even
falling into
their active, young parent stars.
About 1,500 light-years away, the
Orion Nebula is the closest
large stellar nursery.
At that distance, this Chandra image spans about 10 light-years.
APOD: 2005 April 20 - Barnard's Loop Around Orion
Explanation:
Why is the
belt of Orion surrounded by a bubble?
Although glowing like an
emission nebula,
the origin of the bubble, known as
Barnard's Loop, is currently unknown.
Progenitor hypotheses include the
winds
from bright Orion stars and the
supernovas
of stars long gone.
Barnard's Loop is too faint to be identified with the unaided eye.
The nebula
was discovered only in 1895 by
E. E. Barnard on long duration film exposures.
Orion's belt is seen as the
three bright stars across the center of the image,
the upper two noticeably blue.
Just to the right of the
lowest star in Orion's belt is a slight indentation in an
emission nebula that, when seen at
higher magnification, resolves into the
Horsehead Nebula.
To the right of the belt stars is the bright, famous, and photogenic
Orion Nebula.
APOD: 2005 April 19 - Orion in Infrared
Explanation:
Do you recognize the constellation Orion?
This striking but unfamiliar looking picture of the familiar Orion region of the sky was produced using survey data
from the now-defunct
InfraRed Astronomical Satellite (IRAS).
The above image
combines information recorded at three different invisible
infrared wavelengths and covers about 30x24 degrees on the sky.
Most of Orion's visually impressive stars
don't stand out, but bright
Betelgeuse
does appear as a small bright purplish dot on the lower left.
The bright region on the right contains the
Great Nebula in Orion,
while the bright region just above the image bottom is the
Rosette Nebula.
Surrounding these regions
are a jumble of chaotic glowing gas and
dark dust
jettisoned by stars forming and exploding over millions of years.
APOD: 2005 March 21 - Orion's Horsehead Nebula
Explanation:
The Horsehead Nebula
is one of the most famous nebulae on the sky.
It is visible as the dark indentation to the red emission nebula
seen above and to the right of center in the
above photograph.
The bright star on the left is located in the
belt of the familiar constellation of Orion.
The horse-head
feature is dark because it is really an opaque
dust cloud which lies in
front of the bright red emission nebula.
Like clouds in Earth's atmosphere, this cosmic cloud has assumed a
recognizable shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance.
The emission nebula's red color is caused by
electrons recombining with
protons to form
hydrogen atoms.
Also visible in the picture are blue reflection nebulae,
which preferentially
reflect the blue light from
nearby stars.
APOD: 2005 March 10 - NGC 1499: California Nebula
Explanation:
Drifting through the Orion Arm of the spiral Milky Way Galaxy,
this cosmic cloud
by chance echoes the
outline of California on the west coast of the United States.
Our own Sun also lies within the Milky Way's
Orion
Arm, only about 1,500 light-years from the California Nebula.
Also known as NGC 1499, the classic emission nebula
is around 100 light-years long.
It glows with the red light characteristic of hydrogen atoms
recombining with
long
lost electrons, stripped away (ionized)
by energetic starlight.
In this case, the star most likely providing the energetic
starlight is the bright, hot, bluish Xi Persei,
just right of the nebula and above picture center.
Fittingly,
this
composite picture was made with images from a telescope
in California - the 48-inch (1.2-meter)
Samuel
Oschin Telescope - taken as a part of the
second National Geographic
Palomar Observatory
Sky Survey.
APOD: 2005 January 6 - UKIRT: Aloha Orion
Explanation:
At the edge of a dense
molecular
cloud, filaments of gas, cosmic dust, and
a multitude of young stars beckon in this penetrating image
of the Orion Nebula.
Alluring structures in the well-known star forming region
are
revealed here in infrared light as viewed
by a new Hawaiian eye - WFCAM - a powerful wide field camera
commissioned at the United Kingdom Infrared Telescope
(UKIRT)
on Mauna Kea.
Only a fraction
of WFCAM's full field, this
picture covers about 11 light-years at the 1,500 light-year
distance of the nebula.
In the image, otherwise invisible
infrared
light has been
mapped into visible colors.
Red represents narrow-band infrared emission from hydrogen
molecules at a wavelength of 2.12
microns,
green is emission at 2.2 microns, and
blue is emission at 1.25 microns.
Visible light has a wavelength of about 0.5 microns
(micrometers).
APOD: 2004 December 22 - Comet, Meteor, Nebula, Star
Explanation:
Several wonders of the late-year northern sky
appeared together for a few fleeting moments on December 13.
On the bottom left, just above the hill, is blue
Sirius, the brightest star in the sky.
Above Sirius and slightly to the right of the
belt of Orion is the red
Orion Nebula,
one of the most famous nebulas on the sky.
Below and to the right of the
Orion Nebula streaks a yellow meteor,
although moving in the wrong direction to be from the
Geminids meteor shower
that peaked the night.
Finally, above and to the right of the meteor is
Comet Machholz, whose
coma appears here relatively green.
Since the time since this image was taken over a Californian hill, the
Geminid meteor has long since evaporated.
Comet Machholz has brightened and moved to the north.
Sirius, however, will remain in the constellation of Canis Major indefinitely.
APOD: 2004 September 27 - The Great Nebula in Orion
Explanation:
The Great Nebula in Orion is a colorful place.
Visible to the unaided eye, it appears as a small
fuzzy patch in the constellation of Orion.
Long exposure, digitally sharpened images like this, however, show the
Orion Nebula to be a busy neighborhood of young stars, hot gas, and dark
dust.
The power behind much of the
Orion Nebula
(M42) is the
Trapezium -
four of the brightest stars in the nebula.
Many of the
filamentary structures visible are actually
shock waves - fronts
where fast moving material encounters slow moving gas.
The Orion Nebula spans about 40 light years and is
located about 1500
light years away in the same
spiral arm of
our Galaxy as the
Sun.
APOD: 2004 July 13 - Orion Nebula in Oxygen, Hydrogen, and Sulfur
Explanation:
The Great Nebula in Orion, an
immense, nearby starbirth region,
is arguably the most famous of all astronomical nebulae.
The
Orion Nebula,
also known as M42, is
shown above through
ultraviolet
and blue filters augmented with three exact colors specifically emitted by
hydrogen,
oxygen, and
sulfur.
In addition to housing a bright open cluster of stars known as the
Trapezium, the
Orion Nebula contains many
stellar nurseries.
These nurseries contain glowing gas, hot young stars,
proplyds, and
stellar jets spewing material at high speeds.
Many of the filamentary structures visible in
this image are actually
shock waves - fronts where fast moving material encounters slow moving gas.
The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same
spiral arm of our Galaxy as the Sun.
APOD: 2004 March 25 - An Orion of a Different Color
Explanation:
Look up into the sky tonight, and even with a good telescope
you won't come across a sight quite like this one.
It is a familiar object though, the grand stellar nursery
known as the
Orion Nebula.
But the
striking picture combines
images taken through three separate filters, each designed
to record different
emission lines - light from Sulfur,
Oxygen, and Hydrogen atoms glowing in the
tenuous nebular gas.
At such low
densities, Sulfur and Hydrogen atoms emit red colors
while Oxygen glows green.
To distinguish their contributions in the final image, Sulfur was
assigned to red, Hydrogen to green, and Oxygen to blue,
a color scheme used
in mapped-color images of other astronomical nebulae as well.
While the result is very different from what the eye
might see,
the image is still both beautiful and scientifically valuable,
tracing
elements and conditions within the nearby
star forming region.
APOD: 2004 March 15 - The Orion Nebula from CFHT
Explanation:
Few astronomical sights excite the imagination like the
nearby stellar nursery known as the
Orion Nebula.
The Nebula's glowing gas surrounds hot young stars at
the edge of an immense interstellar
molecular cloud only 1500 light-years away.
The Great Nebula in Orion can be
found with the unaided eye just below and to the left of the
easily identifiable
belt of three stars in the popular constellation Orion.
The above image from the
3.6-meter Canada-France-Hawaii Telescope atop a
dormant volcano in Hawaii brings out
Orion's detail in spectacular fashion.
Buried in the complex nebulosity are the bright stars of the
Trapezium in
Orion's heart, the sweeping lanes of
dark dust that cross the center,
the pervasive red glowing hydrogen gas,
and the
blue tinted dust
that reflects the light of newborn stars.
The whole Orion Nebula cloud complex, which includes the
Horsehead Nebula,
will slowly disperse over the next 100,000 years.
APOD: 2004 February 19 - McNeil's Nebula
Explanation:
It was a clear, cold western
Kentucky night on January 23rd as
seasoned amateur astronomer Jay McNeil tried out his recently acquired 3-inch
refracting telescope by
imaging
the area around a familiar object, the
M78 reflection nebula in Orion.
Days later while processing the images, he noted a substantial
but totally unfamiliar nebulosity in the region!
With a little help from his friends,
his
amazing discovery
is now recognized as a newly visible reflection nebula surrounding a
newborn star -- McNeil's Nebula.
Pictured here at the center of
this
close-up, McNeil's Nebula with
its illuminating young star at the
tip, do not appear in images of the area before September 2003.
The emergence
of McNeil's Nebula is a rare event to witness and
astronomers are eagerly following its development, but Orion
will soon lie too close to the Sun in the sky, interrupting
further observations for several months.
The
Orion nebula complex itself is around 1,500 light-years away.
At that distance, the above image spans less than 10 light-years.
APOD: 2004 January 15 - An Orion Deep Field
Explanation:
Adrift 1,500 light-years away in one of
the night sky's
most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
They both appear in this stunning composite digital image
assembled from over 20 hours of data that includes exposures
filtered to record emission from hydrogen
atoms.
The view reveals extensive
nebulosities associated with
the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
The magnificent emission region, the
Orion
Nebula (aka M42), lies at the
upper right of the picture.
Immediately to its left are a cluster of
of prominent bluish
reflection nebulae sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow at the lower left.
Alnitak is the easternmost star in Orion's belt and
is seen as the brightest star to the left of the Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Fainter tendrils of glowing hydrogen gas are easily traced
throughout the region in
this
Orion deep field.
APOD: 2003 December 29 - The Witch Head Nebula
Explanation:
Double, double toil and trouble;
Fire burn, and cauldron bubble -- maybe
Macbeth should have consulted the Witch Head Nebula.
This suggestively shaped
reflection nebula
is associated with the
bright star Rigel in the
constellation Orion.
More formally known as
IC 2118,
the Witch Head Nebula glows primarily by light reflected from
Rigel, located just outside the top right corner of the
above image.
Fine dust
in the nebula reflects the light.
The blue color is caused not only by
Rigel's blue color but because the
dust grains reflect blue light more efficiently than red.
The same
physical process causes
Earth's daytime sky to appear blue,
although the scatterers in
Earth's atmosphere are molecules of
nitrogen and
oxygen.
The nebula lies about 1000 light-years away.
APOD: 2003 November 15 - LL Orionis: When Cosmic Winds Collide
Explanation:
This arcing, graceful structure is actually a
bow shock about half a
light-year across, created as the wind from young star LL Orionis
collides with the
Orion Nebula flow.
Adrift in Orion's
stellar nursery
and still in its formative years,
variable star LL Orionis produces a wind more
energetic than
the wind from our own
middle-aged sun.
As the fast stellar wind runs into slow moving gas a shock front is
formed, analogous to the
bow
wave of a boat moving through water or
a plane traveling at supersonic speed.
The slower gas is flowing away from the Orion Nebula's hot central star
cluster, the
Trapezium, located off the lower right hand edge
of the picture.
In three
dimensions,
LL Ori's wrap-around shock front is shaped like a
bowl that appears brightest when viewed along the "bottom" edge.
The complex
stellar nursery in Orion shows a myriad of similar
fluid
shapes associated with
star formation, including
the bow shock surrounding a faint star at the upper right.
Part of
a mosaic
covering the
Great Nebula
in Orion, this composite color image was recorded
in 1995 by the Hubble Space Telescope.
APOD: 2003 November 5 - The Lynx Arc
Explanation:
While chasing the spectrum of a mysterious arc in a cluster of
galaxies within the obscure northerly
constellation
Lynx, astronomers have
stumbled upon the most massive and distant star-forming region
ever discovered.
The notably red "Lynx arc" lies right of center in
this
color image of the galaxy cluster, a composite of
Hubble Space Telescope and ground-based data.
While the galaxy cluster lies about 5 billion
light-years distant,
spectroscopic studies
show that the arc itself is actually a distorted
image of an even more distant but enormous star-forming region.
The image is formed as the closer galaxy cluster's
gravity
bends light
like a magnifying lens, an effect explained by Einstein's
theory of gravity.
In fact, the monster star-forming region is nearly
12 billion
light-years away
and about a million times brighter than the
more familiar stellar nursery, the
Orion Nebula.
Estimates are that the star-forming region seen as the
Lynx arc contains about a million massive, hot stars, compared
to the four stars which power the
Orion Nebula's glow.
Stars within the Lynx arc are more than twice as hot
as the Orion Nebula's central stars
and were formed when
the Universe was a mere 2 billion years old.
Still, astronomers believe that the
first stars were
formed at even earlier times.
APOD: 2003 October 23 - Cygnus Nebulosities
Explanation:
Looking toward the constellation
Cygnus,
a stunning and complex region of nebulae strewn along
the plane of our
Milky Way
galaxy is revealed in this unique
wide-angle sky view.
Recorded with a filter designed to transmit
light emitted by hydrogen atoms,
the image emphasizes
cosmic gas clouds in a 34 by 23 degree field centered
on the well known Northern Cross asterism.
Bright, hot, supergiant
star
Deneb (the top of the cross)
and popular
celestial sights such as the North
America and Pelican
emission regions, the IC 1318
"butterfly",
and the Crescent
and Veil nebulae
can be identified by placing your cursor over the image.
Silhouetted by the glowing
interstellar
clouds and crowded star
fields, the dark Northern Coal Sack is also visible, part
of a series of obscuring dust clouds forming the Great Rift
in
the Milky Way.
These Cygnus nebulosities are all located about 2,000 light-years
away.
Along with the Sun, they lie within the
Orion
spiral arm of our galaxy.
APOD: 2003 October 7 - The Colorful Horsehead Nebula
Explanation:
While drifting through the cosmos, a magnificent interstellar
dust cloud became sculpted by stellar winds and radiation to
assume a recognizable shape.
Fittingly named the Horsehead Nebula, it is embedded in the vast and complex
Orion Nebula.
The dark
molecular cloud, roughly 1,500 light years distant, is cataloged as
Barnard 33
and is visible only because its obscuring dust is
silhouetted against the bright
emission nebula IC 434.
The bright blue
reflection nebula
NGC 2023 is visible on the lower left.
The prominent horse head
portion of the nebula is really just part of a
larger cloud of
dust which can be seen extending
toward the bottom of the picture.
A potentially rewarding but difficult object to view with a
small telescope, this gorgeous
representative-color image was taken by the large 3.6-m
Canada-France-Hawaii Telescope
in Hawaii,
USA.
APOD: 2003 October 2 - Reflections on the 1970s
Explanation:
The 1970s
are
often overlooked.
In particular, the beautiful grouping of reflection nebulae
NGC 1977,
NGC 1975, and NGC 1973 in Orion are
often overlooked in favor of
the substantial stellar nursery better known as the Orion Nebula.
Found along the sword of Orion just north
of the
bright Orion Nebula complex, these nebulae are also associated
with Orion's giant
molecular cloud which lies about
1,500 light-years away, but
are dominated by the characteristic blue color of interstellar
dust reflecting light from hot young stars.
In this sharp
color image a portion of the Orion Nebula appears
along the bottom border with the cluster
of reflection nebulae
at picture center.
NGC 1977 stretches across the field just below center,
separated from NGC 1973 (above right) and NGC 1975 (above left)
by dark regions laced with faint red emission from
hydrogen atoms.
Taken together, the dark regions suggest to many the
shape of a running man.
APOD: 2003 July 13 - The Horsehead Nebula
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a
photographic plate in the late 1800s.
The red glow originates from
hydrogen gas predominantly behind the nebula,
ionized by the nearby bright star
Sigma Orionis.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the
process of forming.
Light takes about 1500 years to reach us from the
Horsehead Nebula.
The
above image was taken with the
0.9-meter telescope at
Kitt Peak National Observatory.
APOD: 2003 April 4 - Clusters and Nebulae of the Hexagon
Explanation:
At first, the bright stars of the large
asterism
known as the (northern)
Winter Hexagon might be hard to pick out in this gorgeous
deep sky mosaic from December 2002.
But placing your cursor over the picture will reveal the hexagon's
outlines and the bright clusters and nebulae along
a stunning portion of
the Milky Way
opposite the
galactic center.
The celestial highlights include
M42
(aka the Great Nebula of Orion),
Orion's Horsehead nebula,
the Rosette and
Cone nebulae, and nearby star clusters
M45 (Pleiades) and Gemini's own
M35.
For now, this hexagon is sinking low in western
evening skies.
APOD: 2003 March 4 - In the Center of the Lagoon Nebula
Explanation:
The center of the Lagoon Nebula is busy with the
awesome spectacle of star formation.
Visible in the lower left, at least two long funnel-shaped clouds,
each roughly half a light-year long, have been formed by extreme
stellar winds
and intense energetic starlight.
The tremendously bright nearby star,
Hershel 36, lights the area.
Vast walls of dust
hide and redden other hot young stars.
As energy from these stars pours into the
cool dust and gas,
large temperature differences in adjoining regions
can be created generating
shearing winds which may cause the funnels.
This picture, spanning about 5 light years, was taken in 1995 by the
orbiting Hubble Space Telescope.
The
Lagoon Nebula, also known as
M8, lies about 5000
light years distant toward the
constellation of
Sagittarius.
APOD: 2003 March 2 - In the Center of the Trapezium
Explanation:
Start with the constellation of
Orion.
Near Orion's belt is a fuzzy area known as the
Great Nebula of Orion or
M42.
In this nebula is a bright
star cluster known as the
Trapezium, shown above.
New stellar systems are forming there in gigantic globs of gas and
dust known as
Proplyds.
Looking closely at the above picture also reveals
that gas and dust surrounding some of the
dimmer stars
appears to form structures that point away from the
brighter stars.
The above false color image was made by combining
several exposures from the orbiting
Hubble Space
Telescope.
APOD: 2003 February 25 - M42: Wisps of the Orion Nebula
Explanation:
The Great Nebula in Orion, an immense, nearby
starbirth region,
is probably the most famous of all
astronomical nebulas.
Here, glowing gas surrounds hot young stars at the edge of an
immense interstellar
molecular cloud only 1500
light-years away.
In the above deep image, faint wisps and sheets of
dust and gas are particularly evident.
The Great Nebula in Orion can be found with the
unaided eye just below and to the left of the
easily identifiable
belt of three stars in the popular constellation
Orion.
In addition to housing a bright
open cluster of stars known as the
Trapezium, the
Orion Nebula contains many
stellar nurseries.
These nurseries contain
hydrogen gas, hot young stars,
proplyds, and
stellar jets
spewing material at high speeds.
Also known as
M42, the
Orion Nebula spans about 40 light years and is located in the same
spiral arm of
our Galaxy as the
Sun.
APOD: 2003 February 7 - Orion on Film
Explanation:
Orion, the Hunter, is one of the most easily recognizable
constellations
in planet Earth's night sky.
But Orion's stars and
nebulae don't look
quite as colorful to the
eye as they do in
this lovely photograph, taken last month from Vekol Ranch south
of
Phoenix, Arizona, USA.
The celestial scene was recorded
in a five minute
time exposure using high-speed color print film
and a 35mm camera mounted on a small telescope.
In the picture, cool red giant
Betelgeuse
takes on a yellowish tint as the brightest star
at the upper left.
Otherwise Orion's hot blue stars are numerous, with
supergiant Rigel balancing Betelgeuse at the
lower right, Bellatrix at the upper right, and
Saiph at the lower left.
Lined up in Orion's belt (left to right) are
Alnitak, Alnilam, and Mintaka all about 1,500 light-years away,
born of the constellation's well studied
interstellar
clouds.
And if the middle "star" of Orion's sword looks reddish and fuzzy
to you, it should.
It's the stellar nursery known as the
Great Nebula of Orion.
APOD: 2003 January 29 - Orion's Horsehead Nebula
Explanation:
The Horsehead Nebula
is one of the most famous nebulae on the sky.
It is visible as the dark indentation to the red emission nebula
seen above and to the right of center in the
above photograph.
The bright star on the left is located in the
belt of the familiar constellation of Orion.
The
horse-head
feature is dark because it is really an opaque
dust cloud which lies in
front of the bright red emission nebula.
Like clouds in Earth's atmosphere,
this cosmic cloud has assumed a recognizable shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance.
The emission nebula's red color is caused by
electrons recombining with
protons to form
hydrogen atoms.
Also visible in the picture are blue reflection nebulae,
which preferentially
reflect the blue light from
nearby stars.
APOD: 2003 January 21 - The Reflecting Dust Clouds of Orion
Explanation:
In the vast
Orion Molecular Cloud complex,
several bright blue nebulas are particularly apparent.
Pictured above are two of the most prominent
reflection nebulas -
dust clouds lit by the
reflecting light of bright embedded stars.
The more famous nebula is
M78,
on the upper right, cataloged over 200 years ago.
On the lower left is the lesser known
NGC 2071.
Astronomers continue to
study these
reflection nebulas to better understand how interior stars form.
The Orion complex
lies about 1500 light-years distant, contains the
Orion and
Horsehead nebulas,
and covers much of the
constellation of Orion.
APOD: 2002 December 20 - Colorful Clouds of Orion
Explanation:
Revisiting one of the most
famous nebulae in
planet Earth's night sky,
astrophotographer
Robert Gendler has constructed this stunning,
color-enhanced mosaic
of the region surrounding the
Great
Nebula in Orion.
As seen here, the
clouds of Orion are dominated by the
reddish emission nebula M42
near the bottom of the image,
with blue reflection nebulae, including
NGC 1977, near the top.
Strewn with dust lanes and dark nebulae,
the striking cosmic apparitions
surrounding Orion's
stellar nurseries are about 1,500 light-years away and are
themselves several light-years across.
Located at the edge of a giant molecular
cloud complex
spanning hundreds of light-years, these nebulae represent only a small,
but very visible(!), fraction of this region's wealth of
interstellar
material.
Within these colorful clouds of Orion,
astronomers have also
identified what appear to be numerous
infant solar systems.
APOD: 2002 August 29 - The Pelican in the Swan
Explanation:
The Pelican Nebula, also known as IC 5070, lies about 2,000 light-years
away in the high and far-off
constellation of Cygnus, the Swan.
This picture spans a portion
of the magnificent nebula about 30 light-years wide.
Fittingly, this cosmic
pelican is found
just off the east "coast" of
the North America Nebula,
another surprisingly familiar looking
emission nebula in Cygnus.
In fact, the Pelican and North America nebulae are part of the same
large star forming region.
The two glowing
nebulae appear separated from our vantage point
by a large obscuring dust cloud running across the upper
left corner in this
gorgeous
color view.
Within the
Pelican
Nebula, dark dust clouds also help define
the eye and long bill, while a
bright front of ionized gas
suggests the curved shape of the head and neck.
Even though it is almost as close as the
Orion Nebula,
the stellar nursery marked by the Pelican and North America
nebulae has
proven complex and difficult to study.
APOD: 2002 May 30 - Orion Nebulosities
Explanation:
Adrift 1,500 light-years away in one of the night sky's
most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
They both appear in this stunning composite color photograph along with
other nebulosities as part
of the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
The magnificent
Orion
Nebula (aka M42) lies at the
bottom of the image.
This emission nebula's
bright central regions were
captured on fast film in a relatively short 30 second exposure.
Above M42
are a cluster of prominent bluish
reflection nebulae
and fainter reddish emission nebulae recorded in additional exposures
lasting up to 40 minutes.
The Horsehead
appears as a dark nebula, a small silhouette
notched against the long red glow at the upper left.
Alnitak is the easternmost star in Orion's belt and
is seen as the brightest star above the Horsehead.
Immediately to Alnitak's left is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
The telescopic
exposures were made from a site in the Southern French Alps
at an altitude of 2,800 meters (a little closer to the stars!)
in September of 2001.
APOD: 2002 April 20 - Orion Nebula: The 2MASS View
Explanation:
Few astronomical sights excite the imagination like the nearby
stellar nursery known as
the Orion Nebula.
The Nebula's glowing gas surrounds hot young stars at the edge of an
immense interstellar molecular cloud only 1,500 light-years away.
This
distinctively detailed image of the Orion Nebula was constructed
using data from the
2 Micron All Sky Survey or 2MASS.
Using
telescopes in the Northern and Southern Hemispheres of
planet Earth,
the
2MASS project has mapped the entire
sky in infrared light.
The wavelength of infrared light is longer than visible light but more
easily penetrates obscuring dust clouds.
2MASS cameras were sensitve to near infrared wavelengths
around 2 microns or about 0.00008 inches.
Visible light has a wavelength of about 0.00002 inches.
Survey
observations in three infrared bands were translated to blue,
green, and red colors to produce this composite image.
APOD: 2002 March 13 - LL Orionis: When Cosmic Winds Collide
Explanation:
This arcing,
graceful structure is actually a bow shock about half a
light-year across, created as the wind from young star LL Orionis
collides with the
Orion Nebula flow.
Adrift in Orion's
stellar nursery
and still in its formative years,
variable star LL Orionis produces a wind more
energetic than
the wind from our own
middle-aged sun.
As the fast stellar wind runs into slow moving gas a shock front is
formed, analogous to the
bow
wave of a boat moving through water or
a plane traveling at supersonic speed.
The slower gas is flowing away from the Orion Nebula's hot central star
cluster, the
Trapezium, located off the lower right hand edge
of the picture.
In three
dimensions,
LL Ori's wrap-around shock front is shaped like a
bowl that appears brightest when viewed along the "bottom" edge.
The complex
stellar nursery in Orion shows a myriad of similar
fluid
shapes associated with
star formation, including
the bow shock surrounding a faint star at the upper right.
Part of
a mosaic
covering the
Great Nebula
in Orion, this composite color image was recorded
in 1995 by the Hubble Space Telescope.
APOD: 2002 February 13 - The Great Nebula in Orion
Explanation:
Few astronomical sights excite the imagination like the
nearby stellar nursery known as the
Orion Nebula.
The Nebula's glowing gas surrounds hot young stars at
the edge of an immense interstellar
molecular cloud only 1500 light-years away.
The Great Nebula in Orion can be
found with the unaided eye just below and to the left of the
easily identifiable
belt of three stars in the popular constellation Orion.
The above image has been contrast balanced to bring out Orion's detail
in spectacular fashion.
Visible simultaneously are the bright stars of the
Trapezium in
Orion's heart, the sweeping lanes of
dark dust that cross the center,
the pervasive red glowing hydrogen gas,
and the
blue tinted dust
that reflects the light of newborn stars.
The whole Orion Nebula cloud complex, which includes the
Horsehead Nebula,
will slowly disperse over the next 100,000 years.
APOD: 2002 February 11 - Reflection Nebula M78
Explanation:
An eerie blue glow and ominous columns of
dark dust highlight
M78, one of the brightest
reflection nebula
on the sky.
M78 is visible with a small telescope toward
the constellation of Orion.
The
dust
not only absorbs light, but also reflects the
light of several bright blue stars that
formed recently in the nebula.
The same type of scattering that colors the
daytime sky further enhances the blue color.
M78 is about five
light-years across.
M78
appears above only as it was 1600 years ago,
however, because that is how long it takes
light to go from
there to here.
M78
belongs to the larger
Orion Molecular Cloud Complex
that contains the
Great Nebula in Orion and the
Horsehead Nebula.
APOD: 2001 December 28 - Starlight Reflections
Explanation:
Interstellar dust grains
often find themselves in a reflective "mood".
Near a bright star, clouds of these dust particles scatter
short wavelengths of visible starlight
more readily than
long wavelengths, producing lovely blue reflection nebulae.
Nine of the more spectacular examples of these dusty, blue
stellar
neighborhoods
have been assembled here by
astrophotographer
Rob Gendler.
From left to right starting with the top row are
NGC 1977 in Orion,
IC2118 (the Witch Head),
and M78 also in Orion.
Across the middle row are,
M20 (Trifid),
NGC 2264 in Monoceros,
and
IC405 (Flaming Star Nebula).
Along the bottom are
NGC 2023 (near
the Horsehead),
NGC 7023 (Iris Nebula),
and finally bright star Merope surrounded by
a veil of dust (NGC 1435).
Merope is one of the seven sisters of the Pleiades.
APOD: 2001 December 16 - The Horsehead Nebula
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a
photographic plate in the late 1800s.
The red glow originates from
hydrogen gas predominantly behind the nebula,
ionized by the nearby bright star
Sigma Orionis.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the
process of forming.
Light takes about 1500 years to reach us from the
Horsehead Nebula.
The
above image was taken with the
0.9-meter telescope at
Kitt Peak National Observatory.
APOD: 2001 December 4 - AE Aurigae: The Flaming Star
Explanation:
Is star AE Aurigae on fire?
Although surrounded by what may look like
smoke, the object known as the "flaming star"
creates energy primarily by
nuclear fusion, like other stars.
Fire, typically defined as the rapid molecular acquisition of
oxygen, happens only when sufficient
oxygen is present and is not important in such high-energy,
low-oxygen environments such as stars.
The material that appears as smoke is mostly
interstellar hydrogen, but does
contain smoke-like dark filaments of carbon-rich
dust grains.
The AE Aurigae region was imaged by the
KPNO
0.9-meter telescope and is
shown above in false but representative colors.
The star
AE Aurigae itself is very bright, young, blue,
and known as a
runaway star
since it appears to have been ejected from the
Orion Nebula
region about 2.7 million years ago.
APOD: 2001 July 22 - NGC 1977: Blue Reflection Nebula in Orion
Explanation:
The
Orion Nebula
is visible to the unaided eye as a fuzzy patch near the famous
belt of three stars in the Orion.
The above picture captures a part of the
Orion Nebula that primarily reflects light from bright
Orion stars.
This
reflection nebula
appears blue because the blue light from the neighboring stars
scatters more efficiently from
nebula gas than does red light.
The dark lanes are composed of mostly
interstellar dust - fine needle-shaped
carbon grains.
APOD: 2001 May 4 - Protoplanetary Survivors in Orion
Explanation:
The
Orion Nebula is a nuturing stellar nursery filled with
hot young stars and their natal clouds of gas and dust.
But for planetary
systems, the active star-forming region can present
a hazardous and inhospitable birthplace.
While the formation of dusty
protoplanetary disks seems
common in Orion, these
Hubble Space Telescope close-up images dramatically reveal
the torturous conditions they must face while trying to grow into
full-fledged planetary systems.
In each case,
a central young star is surrounded by a
disk substantially wider than our solar system.
The disks likely contain material in the process of planet formation.
However, withering ultraviolet radiation from one of Orion's
nearby hot stars is rapidly destroying the disks --
ultimately creating the comet-shaped clouds of glowing gas
seen engulfing the protoplanetary systems.
Planet formation must occur
quickly here, if at all.
Researchers estimate
that about 90 percent of Orion's youngest
protoplanetary disks will not survive the next 100,000 years.
APOD: 2001 April 26 - Horsehead Rides Again
Explanation:
Difficult to see in small telescopes, the Horsehead nebula was
recently
selected by internet voters as a target for
the Hubble Space Telescope.
Above (top) is
Hubble's
detailed view of the
dark cosmic dust cloud, released
to celebrate the 11th anniversary of the workhorse orbiting observatory.
Below it is a
stunning
ground-based view from
the NOAO 0.9 meter telescope at
Kitt Peak National Observatory
which shows the dark Horsehead against a wider edge-on expanse of
glowing gas.
Dramatic dust and gas clouds in and
around
the Horsehead are part of a large,
complex stellar nursery seen towards the
constellation of Orion.
This star forming region is about 1,500 light-years distant and
includes the well known Orion nebula.
The Horsehead nebula is found just south of
Zeta Orionis, the
easternmost star in Orion's belt.
APOD: 2001 February 27 - The Witch Head Nebula
Explanation:
Double, double toil and trouble;
Fire burn, and cauldron bubble -- maybe
Macbeth should have consulted the Witch Head Nebula.
This suggestively shaped
reflection nebula
is associated with the
bright star Rigel in the
constellation Orion.
More formally known as
IC 2118,
the Witch Head Nebula glows primarily by light reflected from
Rigel, located just outside the top right corner of the
above image.
Fine dust
in the nebula reflects the light.
The blue color is caused not only by Rigel's blue
color but because the
dust grains reflect blue light more efficiently than red.
The same
physical process causes
Earth's daytime sky to appear blue,
although the scatterers in
Earth's atmosphere are molecules of
nitrogen and
oxygen.
The nebula lies about 1000 light-years away.
APOD: 2001 February 24 - Infrared Horsehead
Explanation:
This famous
cosmic dust cloud was
imaged in infrared light by the European Space Agency's
Infrared Space Observatory (ISO) satellite.
The false-color picture
shows the bright
infrared emission
from dust and molecular gas in part of
the Orion star forming region
surrounding the
Horsehead Nebula.
In visible light,
the horsehead-shaped dust cloud looks
dark against a background of bright glowing gas.
But in this image, the interstellar infrared glow engulfs
much of the horse's head.
Just above and to the right of center, only the top remains crowned
by a bright, newborn star.
The very bright object at the lower left is the reflection nebula
NGC 2023, a dense concentration of interstellar gas and
dust grains
also associated with newly formed stars.
APOD: 2001 February 16 - Star Forming Region Hubble X
Explanation:
In nearby galaxy NGC 6822,
this glowing emission nebula complex
surrounds bright, massive, newborn stars.
A mere 4 million years young, these stars condensed
from the galaxy's interstellar gas and dust clouds.
The nebular glow is powered by the bright stars' intense
ultraviolet radiation
while its shape is sculpted by the interaction of stellar
winds and radiation with the immense interstellar clouds themselves.
Cataloged as Hubble-X,
many skygazers find the appearance of this extragalactic
star forming region reminiscent of
the most famous stellar nursery in our own galaxy,
the Orion Nebula.
Hubble-X is
intrinsically much brighter than Orion though,
and at a distance of
1.6 million light-years it is about 1,000 times farther away.
Hubble-X is also about 100 light-years across
compared to 10 light-years
for the Orion Nebula.
Why is it called Hubble-X?
X is the
Roman
numeral 10, this nebula's designation in a catalog
of similar objects for
galaxy NGC 6822.
APOD: 2001 January 30 - The Orion Nebula from VLT
Explanation:
The Great Nebula in Orion is a colorful place.
Visible to the unaided eye, it appears as a small
fuzzy patch in the
constellation of Orion.
But
this image, a representative-color composite of 81
near-infrared light images taken with
VLT's ISAAC, shows the
Orion Nebula to be a busy neighborhood of
young stars, hot gas, and dark dust.
The power behind much of the
Orion Nebula (M42) is the
Trapezium -
four of the brightest stars in the nebula.
The eerie blue glow surrounding the
bright stars pictured here is their own
starlight reflected by nearby
dust.
Dark brown
dust filaments
cover much of the region.
The whole
Orion Nebula cloud complex, which
includes the
Horsehead Nebula,
will slowly disperse over the next 100,000 years.
APOD: 2000 December 29 - The Dark Horsehead Nebula
Explanation:
While drifting through the cosmos
this magnificent interstellar dust cloud,
sculpted by stellar winds and radiation,
has chanced to assume a recognizable shape.
Fittingly named
The Horsehead Nebula
it is embedded in the immense complex of
star forming gas and dust
surrounding the
Orion Nebula some 1,500 light-years distant.
The dark nebula is
cataloged as Barnard 33 and is visible
only because its obscuring dust is silhouetted against
the bright emission nebulae
which lie behind it.
In fact, the prominent
horse head portion of the nebula is really just
part of a larger cloud of dust which can be seen extending off the
bottom of the picture.
A potentially rewarding but difficult object to view with a small
instrument,
this gorgeous color image
is a composite of exposures
made with a digital camera and astronomical
BVR filters
using a 1-meter diameter telescope.
APOD: 2000 November 22 - The Orion Nebula in Hydrogen
Explanation:
The
Great Nebula in Orion can be found just below
and to the left of the easily identifiable
belt of three stars in the popular
constellation Orion.
This fuzzy patch,
visible to the unaided eye,
contains one of the closest
stellar nurseries, lying at a distance of about 1500
light years.
The
above picture highlights red light emitted
by the nebula's hydrogen gas.
Dark
dust
filaments punctuate regions of this glowing hydrogen
gas and reflect light from the
nebula's brightest stars.
Recent observations of the
Orion Nebula by the
Hubble Space Telescope
have located
solar-system sized regions that are
thought to be planet-forming circumstellar disks.
APOD: 2000 November 20 - A 2000 Leonid Through Orion
Explanation:
The Leonid Meteor Shower this year could be
described as good but not great.
During November 17 and 18 the Earth crossed
through several streams of
sand-sized grit
left orbiting the Sun by
Comet Tempel-Tuttle.
Several distinct peaks in
meteor activity were reported,
with rates approaching 400 meteors per hour
for brief periods for some dark locations.
Pictured above, a
Leonid meteor was caught from
Florida
streaking through the
constellation of Orion
on the morning of 2000 November 18.
Visible as a red-tinged smudge to the left of the
three nearly linear stars that compose
Orion's belt is the picturesque star-forming region known as the
Orion Nebula.
Next year, the
Leonids Meteor Shower is expected
by many to be much more active.
APOD: 2000 August 30 - The Brown Dwarfs of Orions Trapezium
Explanation:
The bright stars above are well known as heart
of the Trapezium, an
open cluster
of stars in the center of the
Orion Nebula.
The many dim objects, however, are not well known,
and have come to attention only on
recent images in
infrared light.
These dim objects are thought to be
brown dwarfs and
free-floating planets.
Brown dwarfs are stars too puny to create energy
in their core by
fusing
hydrogen into
helium.
Although many more
brown dwarfs
than hot stars have now been
found in Orion,
their very low masses make them inadequate
to compose much of the
dark matter expected in
galaxies and the
Universe.
The above false-color mosaic
combines infrared and visible light images
of the Trapezium from the Hubble Space Telescope.
Faint brown dwarfs with masses as small as about one percent the mass of the sun
are seen in the infrared data.
Also visible
are complex lanes of hot gas (appearing in blue) and cooler fine
dust that blocks, glows and
reflects nearby starlight.
APOD: 2000 August 27 - Orion's Horsehead Nebula
Explanation:
The Horsehead Nebula
is one of the most famous nebulae on the sky.
It is visible as the black indentation to the red emission nebula
seen just to the right of center of the above photograph.
The bright star near the center is located in the
belt of the familiar constellation of Orion.
The
horse-head
feature is dark because it is really an opaque
dust cloud which lies in
front of the bright red emission nebula.
Like clouds in Earth's atmosphere,
this cosmic cloud has assumed a recognizable shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance.
The emission nebula's red color is caused by
electrons recombining with
protons to form
hydrogen atoms.
Also visible in the picture are blue reflection nebulae,
which preferentially
reflect the blue light from
nearby stars.
APOD: 2000 May 6 - The Heart Of Orion
Explanation:
Newborn stars lie at
at the heart
of the
the Orion Nebula,
hidden from view by the dust and gas of the giant Orion
Molecular Cloud number 1
(OMC-1).
Sensitive to invisible
infrared
wavelengths, Hubble's NICMOS camera
can explore the
interior of OMC-1 detecting the infrared radiation from
infant star clusters and
the interstellar dust and atoms energized by their intense starlight.
In this false color picture,
stars and the glowing dust clouds which also scatter the starlight appear
yellowish orange while emission from hydrogen gas is blue.
The dramatic image reveals a wealth of details, including
many filaments and arcs of gas and dust
-- evidence of violent motions stirred-up by the emerging stars.
The bright object near the center is the massive young star "BN"
(named for its discoverers Becklin and Neugebauer).
The pattern of speckles and
ripples surrounding BN and other bright stars are image artifacts.
APOD: 2000 April 24 - Reflection Nebula M78
Explanation:
An eerie blue glow and ominous columns of
dark dust highlight M78, a bright
reflection nebula
in the constellation of Orion.
The
dust
not only absorbs light, but also reflects the
light of several bright blue stars that
formed recently in the nebula.
The same type of scattering that colors the
daytime sky further enhances the blue color.
M78
is about five
light-years across and visible through a small telescope.
M78
appears above only as it was 1600 years ago,
however, because that is how long it takes
light to go from
there to here.
M78
belongs to the larger
Orion Molecular Cloud Complex
that contains the
Great Nebula in Orion and the
Horsehead Nebula.
APOD: 2000 March 31 - Free Floating Planets In Orion
Explanation:
This false-colour image
of the young Trapezium star cluster in the Orion
Nebula was made with an
infrared camera at wavelengths about
twice as long as visible light.
The infrared data are part of a sensitive survey
of this nearby star forming region in which
astronomers
have identified over 100 extremely low mass
objects -- candidates for
elusive brown dwarf stars.
Brown dwarfs are failed
stars with masses so low (about 8% of the Sun's)
that they can not sustain nuclear hydrogen burning, a sun-like star's main
energy source.
While brown dwarfs are thought to be still massive enough to burn
deuterium for energy,
thirteen of the low mass objects show evidence of
lying below even the deuterium burning limit
(about 1.3% of the
Sun's mass) falling in a range
more commensurate with giant planets.
These drifting, "free-floating planets" are perhaps as little as 8
times as massive as
Jupiter and likely formed along with the cluster stars
a million or so years ago.
They are detectable in the infrared because they
are still hot from formation, but will eventually cool and fade.
If the Trapezium is typical of young
star clusters, then
the survey results suggest that brown dwarfs
and free-floating planets may be fairly common, but there
are not enough to solve the mystery
of dark
matter in the Universe.
APOD: 2000 March 13 - A Panorama of Oddities in Orion A
Explanation:
New stars, fast jets, and shocked gas clouds
all occupy Orion A, a
giant molecular cloud
just south of the
Orion Nebula.
The bright object visible below and slightly left of center of
this recently released picture is the
reflection nebula
NGC 1999.
Wind from NGC 1999's
central star, V380 Orionis, appears to have created the
surrounding billows of red and brown gas.
Several bright young stars illuminate reflecting
dust at the top right of the image.
Jets shoot from dozens of young stars creating glowing
compressed shocked waves known
Herbig-Haro objects.
One such shock is the unusual
Waterfall,
the bright streak on the upper right,
which is a source of unusual
radio waves.
The cone-shaped shock to the Waterfall's
lower right may result from a jet emitted
HH1 and HH2, located 10
light-years away below NGC 1999.
The unusual and energetic oddities that
occur and interact in
star forming regions
are often as complex as they are beautiful.
APOD: 2000 March 2 - NGC 1999: Reflection Nebula In Orion
Explanation:
A dusty bright nebula
contrasts dramatically with a dusty dark nebula in
this Hubble Space Telescope image recorded shortly
after December's orbital
servicing mission.
The nebula, cataloged as
NGC 1999, is a
reflection nebula,
which shines by reflecting light from
a nearby star.
Unlike emission nebulae, whose
reddish glow comes from
excited atoms of gas, reflection nebulae have a
bluish cast
as their interstellar dust
grains preferentially reflect blue
starlight.
While perhaps the most famous reflection nebulae surround
the bright young stars of the Pleiades
star cluster,
NGC 1999's stellar illumination is provided by the embedded variable star
V380
Orionis, seen here just left of center.
Extending right of center, the ominous
dark nebula is actually a condensation of cold molecular
gas and dust so thick and dense that it blocks light.
From our perspective it lies in front of the bright
nebula, silhouetted against the ghostly nebular glow.
New stars will likely form within
the dark cloud, called a Bok globule,
as self-gravity continues to compress its dense gas and dust.
Reflection nebula
NGC 1999
lies about 1500 light-years away in the constellation
Orion,
just south of Orion's well known emission nebula,
M42.
APOD: 2000 February 4 - X-Ray Stars Of Orion
Explanation:
The stars of Orion shine brightly
in northern winter skies where
the constellation
harbors the closest large stellar nursery,
the Great Nebula of Orion, a mere 1500 light-years away.
In fact, the apparently bright clump of stars near the center
of this Chandra
X-ray telescope picture of a portion of
the nebula are the massive stars of
the Trapezium - the
young star cluster which powers much of the nebula's
visible-light glow.
But the sheer number of other stars seen in
this X-ray image, which
spans about 10 light-years, has surprised and delighted astronomers
and
this picture was recently touted
as the richest field of X-ray sources ever recorded
in a single observation.
The picture does dramatically illustrate that
young stars are prodigious sources
of X-rays,
thought to be produced in hot
stellar coronas and
surface flares in a young star's strong magnetic field.
Our middle-aged Sun
itself was probably thousands of times
brighter in X-rays when, like
the Trapezium stars, it was
only a few million years old.
The dark lines through the image are instrumental artifacts.
APOD: November 29, 1999 - Arcs and Jets in Herbig Haro 34
Explanation:
Some features of HH-34 are understood -- some are not.
At the core of Herbig-Haro 34 lies a seemingly typical young star.
This star, though, somehow ejects energetic "bullets" of
high-energy particles,
appearing as red streaks toward the lower right of the
this image.
Astronomers speculate that a burst of these particles might
rebound when gas from a
disk
surrounding the star momentarily collapses onto the star.
Visible near the end of each
light-year long
jet is a glowing cap.
HH-34 lies about 1500 light-years away in the
Orion Nebula star-forming region.
The cause of the large arc of gas on the upper left known as
the waterfall remains unexplained.
APOD: October 26, 1999 - 30 Doradus: The Tarantula Nebula
Explanation:
30 Doradus is an immense star forming region in a nearby galaxy known
as the Large Magellanic Cloud.
Its
spidery appearance is responsible for its popular name, the
Tarantula Nebula, except that
this tarantula is about 1,000 light-years across, and
165,000 light-years away in the southern constellation
Dorado.
If it were at the distance of the
Orion Nebula,
the nearest stellar nursery to Earth, it
would appear to cover about 30 degrees
on the sky or about 60
full moons.
The
above image was taken with the
Big Throughput Camera
and is shown in representative colors.
The spindly arms of the
Tarantula Nebula surround the
NGC 2070 star cluster
which contains some of the intrinsically brightest,
most massive stars known.
This celestial
Tarantula is also seen near the site of the
closest recent Supernova.
APOD: September 24, 1999 - Cometary Globules In Orion
Explanation:
Intense
ultraviolet light from massive, hot stars in
the Orion region has sculpted and
compressed clouds of dust and gas in to
distinctively shaped Cometary Globules.
Seen in this IRAS
infrared image recorded at
a wavelength sensitive to emission from dust, the
elongated globules are easily visible along
with a bright region which corresponds to the
Trapezium star cluster.
Otherwise known as
the Witch Head Nebula,
IC 2118 is the string of globules near the middle right.
Suggestively similar to comets in general appearance only,
Cometary Globules
are interstellar condensations on a vastly
different scale.
These are likely related to star formation episodes in
the Orion
molecular cloud.
Besides those indicated by the arrows,
more comet-shaped clouds or globules are present in this image.
APOD: September 14, 1999 - The Colorful Orion Nebula
Explanation:
The Great Nebula in Orion is a colorful place.
Visible to the unaided eye as a
fuzzy patch in the
constellation of Orion,
this image
taken with the
Big Throughput Camera shows the
Orion Nebula to be a busy neighborhood of
young stars, hot gas, and dark dust.
The power behind much of the
Orion Nebula (M42) is the
Trapezium -
four of the brightest stars in the nebula.
The eerie blue glow surrounding the
bright stars pictured here is their own
starlight reflected by nearby
dust.
Hot oxygen and
hydrogen gases cause the
extended green and pink glows, respectively.
Dark brown
dust filaments
cover much of the region.
The whole
Orion Nebula cloud complex, which
includes the
Horsehead Nebula,
will slowly disperse over the next 100,000 years.
APOD: August 29, 1999 - The Witch Head Nebula
Explanation:
Double, double toil and trouble; Fire burn, and cauldron bubble ...
Maybe
Macbeth should have
consulted the
Witch Head Nebula.
This suggestively shaped reflection nebula is associated with the bright star
Rigel in the constellation
Orion.
More formally known
as IC 2118, the Witch Head Nebula glows primarily by light
reflected from Rigel.
Rigel is located about one photo-width
off the image to the right. Fine
dust in the nebula reflects the light.
The blue color is caused not only by Rigel's blue color but because the
dust grains reflect blue light more efficiently than red.
The same physical process causes
Earth's daytime sky to appear blue, although the scatterers here are
molecules of nitrogen and oxygen. The nebula lies about 1000 light-years away.
APOD: July 13, 1999 - The Flame Nebula in Infrared
Explanation:
What lights up the Flame Nebula? Fifteen hundred
light years away towards the constellation of Orion lies a nebula which,
from its glow and dark
dust lanes,
appears like a billowing fire.
But
fire,
the rapid acquisition of
oxygen, is not what makes this
Flame glow.
Rather the bright star Alnitak, the easternmost star in the
Belt of Orion
visible to the nebula's right,
shines energetic light into the
Flame that knocks electrons away from the
great clouds of hydrogen gas that reside there.
Much of the glow results when the electrons and ionized hydrogen recombine. The above false-color picture of the Flame Nebula (NGC 2024)
was taken in
infrared light, where a young star cluster becomes visible.
The Flame Nebula is part of the
Orion Molecular Cloud Complex,
a star-forming region that includes the famous
Horsehead Nebula.
APOD: June 4, 1999 - NGC 3603: From Beginning To End
Explanation:
From beginning to end, different stages of a star's life appear in
this exciting Hubble Space Telescope picture of the environs
of galactic emission nebula
NGC 3603.
For the beginning, eye-catching "pillars" of glowing
hydrogen at the right signal
newborn stars emerging
from their dense, gaseous, nurseries.
Less noticeable,
dark clouds
or "Bok globules" at the top
right corner are likely part of a still earlier stage, prior to their
collapse to form stars.
At picture center lies a cluster of bright
hot blue stars whose strong
winds and ultraviolet radiation have cleared away nearby material.
Massive and young, they will soon exhaust their nuclear fuel.
Nearing the end of its life, the bright supergiant
star Sher 25 is
seen above and left of the cluster, surrounded by a glowing ring and flanked
by ejected blobs of gas.
The ring structure is reminiscent of
Supernova 1987a and Sher 25
itself may be only a few thousand years from its
own devastating finale.
But what about planets?
Check out the two
teardrop-shaped objects below the cluster
toward the bottom of the picture.
Although larger, these emission nebulae are similar to suspected
proto-planetary disks (proplyds) encompassing stars in the Orion Nebula.
APOD: May 22, 1999 - M42: A Mosaic of Orion's Great Nebula
Explanation:
The Great Nebula in Orion,
an immense, nearby starbirth region, is
probably the most famous of all astronomical nebulae.
Here, 15 pictures from the
Hubble Space Telescope have been mosaicked
to cover the inner 2.5 light years of the nebula and illustrate
its diverse nature.
In addition to housing a bright open cluster of
stars known as the Trapezium, the Orion Nebula contains many
stellar nurseries.
These nurseries contain
hydrogen gas,
hot young stars,
proplyds, and stellar
jets spewing material at high speeds.
Most of the filamentary structures visible in this image are
actually shock waves -
fronts where fast moving material encounters slow moving gas.
Shocks are particularly apparent near the bright stars in the
lower left of the picture.
The Orion Nebula
is about 1500 light years distant, located in the same spiral arm of
our Galaxy as the
Sun.
APOD: May 19, 1999 - The Horsehead Nebula
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a photographic plate in the late 1800s.
The red glow originates from
hydrogen gas predominantly behind the nebula,
ionized by the nearby bright star Sigma Orionis.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the
process of forming.
Light takes about 1500 years to reach us from the
Horsehead Nebula. The
above image was taken with the
0.9-meter telescope at
Kitt Peak National Observatory.
APOD: April 6, 1999 - NGC 6334: The Bear Claw Nebula
Explanation:
NGC 6334 is a cloud of gas and dust that
appears to be forming massive stars.
At 5500 light-years away, the
Bear Claw Nebula, as it has also been dubbed,
is more than three times as distant as the
Orion Nebula, but still close enough for detailed study.
The Bear Claw Nebula can be found towards the constellation of
Scorpius.
In visible light, ionized gas makes
NGC 6334 look quite red.
The above false-color photograph, however, was taken in
infrared light. There, the glow of starlight absorbing
dust is more apparent
(depicted in blue).
Current research
indicates that the bright sources are
very young and massive stars.
These stars emit light so energetic and intense
that it destroys fine grains of
dust in their
immediate vicinity, creating an abundance of
ionized gas (depicted in red).
APOD: March 2, 1999 - The Kleinmann Low Nebula
Explanation:
The most active part of the
Orion Nebular Cloud Complex
is an area known as the
Kleinmann-Low Nebula.
There, a cluster of young and forming stars
is embedded in a
molecular cloud filled with
dust.
In visible light, the dark dust blocks much of Orion KL's light, but in the
infrared light of the above photograph, the area seems literally to explode.
Hot
stellar winds flowing off massive young stars in
Orion KL region permeate and heat surrounding gas, causing
finger-like intrusions.
Near the center of Orion KL is
IRc2, a particularly active star estimated to have over
30 times the mass of
our Sun.
Radio telescopes have
recently detected unusual emission from water molecules -
maser radiation from the Kleinmann-Low Nebula.
APOD: February 2, 1999 - The Orion Nebula from Subaru
Explanation:
The Orion Nebula (M42) shows a host of treasures when viewed in
infrared light.
Some stars in the
Trapezium, an
open cluster
of stars at the center, are only visible in infrared light.
The orange feature above center is called the Kleinman-Low Nebula,
and appears greatly affected by newly forming central star IRc2.
The blue emission in this representative color photograph
is caused by hot gas ionized by the
Trapezium stars.
This is one of the
first photographs ever taken through Japan's new
Subaru Telescope.
APOD: January 15, 1999 - Reflections Of Orion
Explanation:
The Orion Nebula and
its surroundings present skygazers with a
wondrous jumble of newborn stars, gas, and dust.
Emission nebulae - glowing energized clouds of gas, and
reflection nebulae - dust clouds
shining by reflected starlight, abound at this
photogenic
cosmic location a mere 1,500 light-years or so away.
This telescopic image reveals an
intriguing nebulosity which seems to consist of dust clouds
illuminated not by starlight but by the light of the
Orion Nebula itself.
In non-telescopic views, the bright group of stars near the top
appear as the northernmost star in Orion's sword.
They are seen here illuminating the nearby dust clouds.
Yet the yellowish streamers of dust across the middle reflect
the light of the Orion Nebula,
which lies just off the bottom edge of the photo.
APOD: January 3, 1999 - Orion's Horsehead Nebula
Explanation:
The Horsehead Nebula
is one of the most famous nebulae on the sky. It is visible
as the black indentation to the red emission nebula
seen just to the right of center of the above photograph. The
bright star near the center is located in the belt of the familiar
constellation of Orion.
The horse-head feature is dark because it is really an opaque
dust cloud which lies in
front of the bright red emission nebula.
Like clouds in Earth's atmosphere,
this cosmic cloud has assumed a recognizable shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance. The emission nebula's
red color is caused by electrons recombining with protons to form
hydrogen atoms. Also
visible in the picture are blue reflection nebulae,
which preferentially
reflect the blue light from nearby stars.
APOD: November 26, 1998 - Meteor Milky Way
Explanation:
The bold, bright
star patterns of Orion (right) are a
familiar sight to even casual skygazers.
But this gorgeous color photo also features a subtler
spectacle - the faint stars
of the Milky Way.
A broad region of
the Milky Way
runs vertically through the picture
with the striking
red Rosette Nebula in bloom left of center.
Cutting across this dim, diffuse band of stars which lie along
the plane of our Galaxy is a meteor streak.
It seems to pass just under
the red-orange giant star Betelgeuse at
Orion's shoulder.
Astrophotographer
Jeff Medkeff recorded
this and other beautiful time exposures from
a dark sky countryside southeast of Sierra Vista, Arizona USA,
during
November's Leonid
meteor shower.
APOD: August 6, 1998 - Infrared Horsehead
Explanation:
This famous
cosmic dust cloud was imaged in infrared light by
the European Space Agency's
Infrared Space Observatory (ISO) satellite.
The false-color picture
shows the bright
infrared emission
from dust and molecular gas
in part of
the Orion star forming region
surrounding
the Horsehead Nebula.
In visible light, the
horsehead-shaped dust cloud looks
dark against a background of bright glowing gas.
But in this image, the interstellar infrared glow engulfs
much of the horse's head.
Just above and to the right of center, only the top remains crowned
by a bright, newborn star.
The very bright object at the lower left is the reflection nebula
NGC 2023, a dense concentration of interstellar gas and
dust
which is also associated with newly formed stars.
APOD: June 12, 1998 - Orion Nebula: The 2MASS View
Explanation:
Few astronomical sights excite the imagination like the nearby
stellar nursery known as
the Orion Nebula.
The Nebula's glowing gas surrounds hot young stars at the edge of an
immense interstellar molecular cloud only 1,500 light-years away.
This distinctively detailed image of the Orion Nebula was constructed
using data from the
2 Micron All Sky Survey or 2MASS.
Now underway with
telescopes in the Northern and Southern Hemispheres of
planet Earth,
the 2MASS project will map the entire
sky in infrared light.
The wavelength of infrared light is longer than visible light but more
easily penetrates obscuring dust clouds.
2MASS cameras are sensitve to near infrared wavelengths
around 2 microns or about 0.00008 inches.
Visible light has a wavelength of about 0.00002 inches.
Survey observations in three infrared bands were translated to blue,
green, and red colors to produce this composite image.
APOD: June 4, 1998 - Comet SOHO and Nebulae in Orion
Explanation:
Astrophotographer Michael Horn
captured this
gorgeous view of
comet SOHO in the dark night sky above
Wandibindle, Queensland, Australia on May 23rd.
On this date,
comet SOHO
was moving against the background of
the nebula-rich constellation of Orion.
South is up in the
picture which shows SOHO's bright head or
coma and long
tail extending past
the glowing gas clouds and dark dust lanes of
the Flame and
Horsehead nebulae.
Alnitak, the bright star above and to the right of the
cometary coma, is also known as Zeta Orionis,
the eastern-most of the three stars in
Orion's belt.
Southern Hemisphere
observers report that comet SOHO has recently
undergone a dramatic increase in brightness.
APOD: April 21, 1998 - Water From Orion
Explanation:
Is Orion all wet?
Recent observations have confirmed
that water molecules now exist in the famous
Orion Nebula,
and are still forming.
The
Orion Nebula (M42, shown above) is known to be composed mostly of
hydrogen gas, with
all other atoms and molecules being comparatively
rare. The nebula is so
vast, though, that even the measured
minuscule production rate creates enough water to fill
Earth's oceans 60 times over every day,
speculate discoverers led by M. Harwit
(Cornell).
The water that composes
comets, the oceans of Earth, and even humans may have been created in a cloud like the Orion Nebula.
APOD: February 9, 1998 - The Witch Head Nebula
Explanation:
Double, double toil and trouble; Fire burn, and cauldron bubble ...
Maybe
Macbeth should have
consulted the
Witch Head Nebula.
This suggestively shaped reflection nebula is associated with the bright star
Rigel in the constellation
Orion.
More formally known
as IC 2118, the Witch Head Nebula glows primarily by light
reflected from Rigel.
Rigel is located about one photo-width
off the image to the right. Fine
dust in the nebula reflects the light.
The blue color is caused not only by Rigel's blue color but because the
dust grains reflect blue light more efficiently than red.
The same physical process causes
Earth's daytime sky to appear blue, although the scatterers here are
molecules of
nitrogen and
oxygen. The nebula lies about 1000 light-years
away.
APOD: February 1, 1998 - NGC 1977: Blue Reflection Nebula in Orion
Explanation:
The
Orion Nebula
is visible to the unaided eye as a fuzzy patch near the famous
belt of three stars in the
constellation
Orion. The
above picture captures a part of the
Orion Nebula that primarily reflects light from bright Orion stars. This
reflection nebula appears blue
because the blue light from the neighboring stars scatters more
efficiently from nebula gas than does red light.
The dark lanes are composed of mostly
interstellar dust - fine needle-shaped
carbon grains.
APOD: January 27, 1998 - The Great Nebula in Orion
Explanation:
The Great Nebula in Orion can be found just below and to
the left of the easily identifiable
belt of three stars in the popular constellation Orion.
This fuzzy patch contains one of the closest stellar nurseries,
lying at a distance of about 1500 light years.
In the above picture, the red region on the left consists of nebulae designated
M42 and M43 and contains the bright
Trapezium
open cluster.
The blue region on the right is a nebula
primarily
reflecting
the light from internal bright stars.
Recent observations of the
Orion Nebula by the
Hubble Space Telescope
have located solar-system sized
star-forming regions.
APOD: December 1, 1997 - Orion: The Big Picture
Explanation:
Orion is big. Some of the stars that form the constellation of Orion are part of a giant gas cloud
complex that stretches over 100 light years and
appears more than 50 times the diameter of the Moon.
Components of this cloud include the
Horsehead Nebula, the
Orion Nebula, the
Trapezium
open cluster, and
small disks
containing stellar systems which are just forming.
At 1500 light years,
Orion is the closest star forming region to Earth.
Close inspection of the photo's center should reveal the
three stars which form the
belt of Orion.
APOD: November 18, 1997 - In the Center of the Trapezium
Explanation:
Start with the constellation of Orion. Below
Orion's
belt is a fuzzy area known as the
Great Nebula of Orion or M42.
In this nebula is a bright star cluster known as the
Trapezium, shown above. New stellar systems are forming there in
gigantic globs of gas and dust known as
Proplyds.
Looking closely at the above picture also reveals that
gas and dust surrounding some of the dimmer stars
appears to form structures that point away from the brighter stars. The
above false color image
was made by combining several exposures from the
Hubble Space Telescope.
APOD: October 25, 1997 - Orion's Horsehead Nebula
Explanation:
The Horsehead Nebula
is one of the most famous nebulae on the sky. It is visible
as the black indentation to the red emission nebula
seen just to the right of center of the above photograph. The
bright star near the center is located in the belt of the familiar
constellation of Orion.
The horse-head feature is dark because it is really an opaque
dust cloud which lies in
front of the bright red emission nebula.
Like clouds in Earth's atmosphere,
this cosmic cloud has assumed a recognizable shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance. The emission nebula's
red color is caused by electrons recombining with protons to form
hydrogen atoms. Also
visible in the picture are blue reflection nebulae,
which preferentially
reflect the blue light from nearby stars.
APOD: June 19, 1997 - HH1/HH2: Star Jets
Explanation:
A cloud of interstellar gas and dust collapses and
a star is born.
At its core temperatures rise,
a nuclear furnace ignites,
and a rotating dusty disk forms
surrounding the newborn star.
According to current understanding,
as material continues to fall onto the disk it is heated and blasted
back out
along the disk's axis of rotation, forming a pair of
high speed jets.
This Hubble Space Telescope image shows two nebulosities
at the ends of opposing jets from a young star.
The bright blobs at either end are where the jet material
has slammed into interstellar gas.
Tip to tip, the distance is about one light-year.
Located near
the Orion Nebula,
these nebulosities have
catalog designations
HH1 and HH2 for their discoverers astronomers
George Herbig and Guillermo Haro.
The nascent star which produced the jets is in the middle, hidden
by a cloud of obscuring dust.
Yet the structures and details visible in
the star jets
offer clues to events which also occured in our own Solar System -
when the Sun was formed from a collapsing interstellar cloud
4.5 billion years ago.
APOD: June 4, 1997 - Tarantula
Explanation:
NGC 2070 is an immense star forming region in a nearby galaxy known
as the Large Magellanic Cloud.
Its spidery appearance is responsible for its popular name,
"The Tarantula Nebula", except that
this tarantula is about 1,000 light-years across, and
165,000 light-years away in
the southern constellation Dorado.
If it were at the distance of
the Orion Nebula,
the nearest stellar nursery to Earth, it
would appear to cover about 30 degrees on the sky or about 60 full moons.
The spindly arms of
the Tarantula Nebula
surround the 30 Doradus Star Cluster
which contains some of the intrinsically brightest, most massive stars known.
This celestial Tarantula is also seen near the site of
the closest recent Supernova.
APOD: May 23, 1997 - The Heart Of Orion
Explanation:
Newborn stars lie at the heart of
the Orion Nebula,
hidden from view by the dust and gas of the giant Orion
Molecular Cloud number 1
(OMC-1).
Sensitive to invisible
infrared wavelengths,
Hubble's recently installed NICMOS camera
can explore
the interior of OMC-1 detecting the infrared radiation from
infant star clusters and
the interstellar dust and atoms energized by their intense starlight.
In this false color picture,
stars and the glowing dust clouds which also scatter the starlight appear
yellowish orange while emission from hydrogen gas is blue.
The dramatic image reveals a wealth of details, including
many filaments and arcs of gas and dust
-- evidence of violent motions stirred-up by the emerging stars.
The bright object near the center is the massive young star "BN"
(named for its discoverers Becklin and Neugebauer).
The pattern of speckles and
ripples surrounding BN and other bright stars are image artifacts.
APOD: May 11, 1997 - M42: A Mosaic of Orion's Great Nebula
Explanation:
The Great Nebula in Orion,
an immense, nearby starbirth region, is
probably the most famous of all astronomical nebulae.
Here, 15 pictures from the
Hubble Space Telescope have been mosaicked
to cover the inner 2.5 light years of the nebula and illustrate
its diverse nature.
In addition to housing a bright open cluster of
stars known as the Trapezium, the Orion Nebula contains many
stellar nurseries.
These nurseries contain
hydrogen gas,
hot young stars,
proplyds, and stellar
jets spewing material at high speeds.
Most of the filamentary structures visible in this image are
actually shock waves -
fronts where fast moving material encounters slow moving gas.
Shocks are particularly apparent near the bright stars in the
lower left of the picture.
The Orion Nebula
is about 1500 light years distant, located in the same spiral arm of
our Galaxy as the
Sun.
APOD: December 7, 1996 - Planetary Systems Now Forming in Orion
Explanation: How do planets form? Astronomers are finding
out by studying one of the most interesting of all astronomical
nebulae known, the Great Nebula in Orion.
Insets to above mosaic
show several planetary systems in
formation. The bottom left insert shows the relative size of
our own Solar System. The Orion Nebula
contains many stellar nurseries. These nurseries contain hydrogen
gas, hot young stars, proplyds, and
stellar jets spewing material at
high speeds. Much of the filamentary structure visible in this
image are actually shock waves
- fronts where fast moving material encounters slow moving gas.
Some shock waves are visible near one of the bright stars in the
lower left of the picture. The Orion Nebula
is located in the same spiral arm of our Galaxy
as is our Sun.
APOD: October 17, 1996 - Proplyds: Infant Solar Systems?
Explanation:
Are planets common in our galaxy? Strong evidence that the
answer is "yes" was provided in
this 1994 image made by the Hubble Space Telescope .
A close-up of the Orion Nebulae,
it reveals what seem to be disks of dust and gas surrounding
newly formed stars.
These fuzzy blobs, called
"proplyds",
appear to be infant solar systems in the
process of formation.
Of the five stars in this field which spans about 0.14 light years,
four appear to have associated proplyds - three bright ones and one dark one
seen in silhouette against the bright nebula.
A more complete survey of 110 stars in the region
found 56 with proplyds.
If extra-solar planetary systems are common place,
are there extra-terrestrial
civilizations out there as well?
APOD: October 2, 1996 - Orion's Horsehead Nebula
Explanation: The Horsehead Nebula
is arguably the most famous nebula on the sky. It is visible
as the black indentation to the red emission nebula
seen just to the right of center of the above photograph. The
bright star near the center is located in the belt of the familiar
constellation of Orion.
The horse-head feature is dark because it is really an opaque
dust cloud which lies in
front of the bright red emission nebula.
Like clouds in Earth's atmosphere,
this cosmic cloud has assumed a recognizable shape by chance.
After many thousands of years, the internal motions of the cloud
will alter its appearance. The emission nebula's
red color is caused by electrons recombining with protons to form
hydrogen atoms. Also
visible in the picture are blue reflection nebulae,
which preferentially reflect the blue light from nearby stars.
APOD: May 23, 1996 - The Violent Star Cluster 30 Doradus
Explanation:
The largest, most violent star forming region known in the whole
Local
Group of galaxies lies in our neighboring galaxy the
LMC. Were 30 Doradus
at the distance of the
Orion Nebula -- a local star forming region -- it
would take up fully half the sky. Also called the
Tarantula Nebula, the red gas indicates a massive
emission nebula, although
supernova remnants and
dark nebula
also exist in
30
Doradus. The bright knot of stars just below
center is called R136 and contains many of the most massive, hottest, and
brightest stars known.
APOD: April 4, 1996 - The Keyhole Nebula Near Eta Carinae
Explanation:
The dark dusty Keyhole Nebula gets its name from its unusual shape.
Designated NGC 3324, the
Keyhole
Nebula is a smaller region superposed on the bright
Eta Carina
Nebula.
The Eta Carina Nebula is the largest nebula in angular extent on the sky,
larger than the famous Orion Nebula,
but its southerly location makes it less familiar to Northern Hemisphere
skywatchers.
The star Eta Carinae
itself is extremely variable and has faded in a mere 150 years - formerly
one of the brightest in the sky it is now invisible
without a telescope.
The nebula created by the star's
19th century outburst has been photographed by the
Hubble Space Telescope.
APOD: March 20, 1996 - NGC 1977: Blue Reflection Nebula in Orion
Explanation:
The
Orion
Nebula is visible to the unaided eye as a fuzzy patch near the
famous belt of three stars in the
constellation Orion. The above picture
captures a part of the
Orion Nebula that primarily reflects light from
bright Orion stars. This
reflection nebula
appears blue because the blue light from the neighboring stars scatters
more efficiently from nebula gas than does red light. The dark lanes are
composed of mostly
interstellar dust
- fine needle-shaped carbon grains.
APOD: November 21, 1995 - M42: Orion Nebula Mosaic
Explanation:
The Great Nebula in
Orion is one of the most interesting of all astronomical nebulae known.
Here fifteen
pictures from the
Hubble Space Telescope have been merged to show
the great expanse and diverse nature of the nebula. In addition to housing
a bright
open cluster of stars known as the
Trapezium, the Orion Nebula contains many
stellar nurseries. These nurseries contain
hydrogen gas,
hot young stars,
proplyds, and stellar
jets spewing material at high speeds. Much of
the filamentary structure visible in this image are actually shock waves -
fronts where fast moving material encounters slow moving gas. Some shock
waves are visible near one of the bright stars in the lower left of the
picture. The
Orion Nebula is located in the same spiral arm of
our Galaxy as is our
Sun. It takes light about 1500 years to
reach us from there.
APOD: September 25, 1995 - Orion's Horsehead Nebula
Explanation:
The black indentation to the red
emission nebula
seen just to the right of
center of the above photograph is one of the most famous features in any
nebulae on the sky. Because of its shape, it is known as the
Horsehead
Nebula. The bright star near the center is
located in the belt of the familiar constellation of Orion.
The horse head feature is dark because it is really a dense
dust cloud which lies
in front of the bright nebula and blocks the light.
Like clouds in our sky, this cosmic cloud has chanced to assume
a recognizable shape. After thousands of years, the
internal motions of the cloud will alter its appearance.
The emission nebula's
red color is caused by electrons recombining with protons to form
hydrogen atoms.
Also visible in the picture are blue
reflection nebulae.
This type of nebula contains dust which
preferentially reflects the blue light of nearby stars.
APOD: July 3, 1995 - The Great Nebula in Orion
Explanation:
The Great Nebula in Orion, M42, can be found on the night sky just below and
to the left of the easily identifiable belt of three stars in the popular
constellation Orion. This nebula is one of the closest stellar nurseries -
where young stars are being formed even now.
Clumps of gas (mostly hydrogen and helium) and dust in the nebula
are squeezed together by their own gravity until they collapse and
form stars.
Some stars we can see here partially obscured by the nebula,
are only about 100,000 years
old - just babies compared to the 5 billion (5,000,000,000) years of
our Sun.