|
Halloween
is a big night for astronomers.
+ Play Audio |
+ Download Audio | +
Historia en Español | +
Email to a friend | + Join mailing list
October 27, 2005: According to the National Retail
Foundation, the most popular Halloween costume last year was
Spiderman. Next was "a princess," followed by witches
and vampires, SpongeBob, Barbie and Harry Potter.
Sounds
about right. But if you read the complete list of top costumes,
you'll notice something missing: astronomers. There are no
Sagans, no Galileos, not even a Hubble.
 And
that's funny, because Halloween is an astronomical holiday.
It
has to do with seasons: Halloween is a "cross-quarter
date," approximately midway between an equinox and a
solstice. There are four cross-quarter dates throughout the
year, and each is a minor holiday: Groundhog Day (Feb. 2nd),
May Day (May 1st), Lammas Day (Aug. 1st), and Halloween (Oct.
31st).
Right:
Red crosses mark the year's cross-quarter dates. [More]
Long
ago, "the Celts of the British Isles used cross-quarter
days to mark the beginnings of seasons," says John Mosley
of the Griffith Observatory in Los Angeles. "Winter began
with Halloween, [or as they called it, 'Samhain']. Halloween
marked the transition between summer and winter, light and
dark -- and life and death."
"On
that one night, according to folklore, those who had died
during the previous year returned for a final visit to their
former homes. People set out food and lit fires to aid them
on their journey -- but remained on guard for mischief the
spirits might do."
And,
so, something astronomical became something spooky. It's not
the first time. Have you heard that comets are bad omens?
Or that a full moon brings out werewolves? Astronomy and superstition
are old friends.
This
year Halloween has a new astronomical significance:
On
Oct. 31st, the planet Mars is making its closest approach
to Earth for the next 13 years. (13 years? Cross
your fingers.) Technically speaking, the moment of closest
approach occurs on Oct. 30th, a day before Halloween, but
the difference in distance between the 30th and the 31st is
too slight to matter.
Trick
or Treaters will notice Mars rising in the east at sunset:
sky map. It
looks like a pumpkin-colored star, so intense that people
in brightly-lit cities can see it. Some say it's blood red,
but maybe that's just Halloween talking.
Mars
will soar almost overhead at midnight (as seen from North
America) and stay "up" all night long. Halloween
2005 is truly the night of Mars.
Above:
Mars rising over Payson Arizona on Oct. 25, 2005. Credit:
Chris Shur.
Because
Mars is so close--only 69 million km away, which is
close on the vast scale of the solar system--it looks great
through a backyard telescope. Lately amateur astronomers have
been watching dust storms swirl around Mars. They've seen
icy-blue clouds gather over the Martian north pole, where
it is winter. And they been sketching and photographing strange
dark markings that dapple the planet's surface.
So--nothing
against Spiderman, mind you--you might wish to reconsider
your costume. Grab a telescope and be an astronomer. It is
Halloween, after all.
SEND
THIS STORY TO A FRIEND
Author: Dr. Tony
Phillips | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
| More
Information |
| Celebrate
This Halloween With Mars At Its Brightest Until 2018
-- (Jack Stargazer)
Wait
a minute! Mars is not the scariest planet in
the Halloween sky. Venus is. Superbright Venus pops
into view even before the twilight sky fades to black.
You can't miss it in the southern sky around sunset.
What
makes it scary? For one thing, Venus has a bad case
of global warming. Its thick carbon dioxide atmosphere
traps solar heat, warming the planet's surface to a
hellish 740 K (872 F). The atmosphere itself is crushing.
Venus' air pressure at "sea level" is 90 times
greater than air pressure on Earth. Oh, and those clouds
floating overhead ... they're laced with sulfuric acid.
If you were teleported to Venus you'd be dissolved,
crushed and melted--not necessarily in that order.
So,
which is the real Halloween planet, Mars or Venus? You
decide.
The
History of Halloween -- (The History Channel)
The
Wheel of the Year -- "Weather Doctor"
Keith C. Heidorn explains the ancient origins of Halloween
and cross-quarter dates.
Cross-quarter
Halloween -- (Clark Planetarium) more about Halloween
and cross-quarter dates.
Most
Popular Halloween Costumes -- (National Retail Foundation)
NASA's
Vision for Space Exploration
|
|
