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The NASA/ESA Hubble Space Telescope has snapped a view of several star generations in the central region of the Whirlpool Galaxy (M51), a spiral region 23 million light-years from Earth in the constellation Canes Venatici (the Hunting Dogs). NASA and the Space Telescope Science Institute have issued a press release explaining the study. Copies of relevant pictures can be obtained from the Institute's archives.
This colorful image from the Hubble Space Telescope shows the collision of two gases near a dying star. Astronomers have dubbed the tadpole-like objects in the upper right-hand corner "cometary knots" because their glowing heads and gossamer tails resemble comets. Although astronomers have seen gaseous knots through ground-based telescopes, they have never seen so many in a single nebula.
Hubble captured thousands of these knots from a doomed star in the Helix nebula, the closest planetary nebula to Earth at 450 light-years away in the constellation Aquarius. Each gaseous head is at least twice the size of our solar system; each tail stretches 100 billion miles, about 1,000 times the Earth's distance to the Sun. The most visible gaseous fragments lie along the inner edge of the star' s ring, trillions of miles from the star at its center. The comet-like tails form a radial pattern around the star like the spokes on a wagon wheel. Astronomers have seen the spoke pattern using ground-based telescopes, but Hubble reveals for the first time the sources of these objects.
Unlike most of the published images of Hyakutake, these Hubble images focus on a very small region near the heart of the comet, the icy, solid nucleus. The Hubble images provide an exceptionally clear view of the near-nucleus region of comet Hyakutake.
The images were image was taken through a red filter with the Wide Field Planetary Camera 2 (in WF mode). The sunward and tailward directions are at approximately the 4 o'clock and 11 o'clock positions, respectively. Celestial North and East are at approximately the 5:30 and 8:30 positions, respectively.
The discovery of a strong radiation signal -- about100 times brighter than even the most optimistic predictions -- was made March 27, 1996, during observations of comet Hyakutake using Germany's orbiting ROSAT satellite.
Discovered in 1930, Pluto has always appeared as nothing more than a dot of light in even the largest earth-based telescopes because Pluto's disk is much smaller than can be resolved from beneath the Earth's turbulent atmosphere. Pluto is 2/3 the size of Earth's Moon but 1,200 times farther away. Viewing surface detail is as difficult as trying to read the printing on a golf ball located thirty-three miles away!
Hubble imaged nearly the entire surface of Pluto, as it rotated through its 6.4-day period, in late June and early July 1994. These images, which were made in blue light, show that Pluto is an unusually complex object, with more large-scale contrast than any planet, except Earth.
Pluto itself probably shows even more contrast and perhaps sharper boundaries between light and dark areas than is shown here, but Hubble's resolution (just like early telescopic views of Mars) tends to blur edges and blend together small features sitting inside larger ones.
The two smaller inset pictures at the top are actual images from Hubble. North is up. Each square pixel (picture element) is more than 100 miles across. At this resolution, Hubble discerns roughly 12 major "regions" where the surface is either bright or dark.
The Larger images (bottom) are from a global map constructed through computer image processing performed on the Hubble data. The tile pattern is an artifact of the image enhancement technique.
Opposite hemispheres of Pluto are seen in these two views. Some of the variations across Pluto's surface may be caused by topographic features such as basins, or fresh impact craters. However, most of the surface features unveiled by Hubble, including the prominent northern polar cap, are likely produced by the complex distribution of frosts that migrate across Pluto's surface with its orbital and seasonal cycles and chemical byproducts deposited out of Pluto's nitrogen-methane atmosphere.
The picture was taken in blue light when Pluto was at a distance of 3 billion miles from Earth.
Credit: Alan Stem (Southwest Research Institute), Marc Buie (Lowell Observatory), NASA and ESA
A video of the deployment of the OAST-FLYER payload by the orbiter robotic arm.
A source of more indepth information about the OAST-FLYER is found at Goddard OAST-FLYER Information
According to one theory for the formation of planetary nebulae, the hourglass shape is produced by the expansion of a fast stellar wind within a slowly expanding cloud which is more dense near its equator than near its poles. What appears as a bright elliptical ring in the center, and at first sight might be mistaken for an equatorially dense region, is seen on closer inspection to be a potato shaped structure with a symmetry axis dramatically different from that of the larger hourglass. The hot star which has been thought to eject and illuminate the nebula, and therefore expected to lie at its center of symmetry, is clearly off center. Hence MyCn18, as revealed by Hubble, does not fulfill some crucial theoretical expectations.
The nebula is a record of the star's final death throes. Initially the ejection of the star's outer layers, when it was at its red giant stage of evolution, occurred at a low rate and was spherical. The Hubble photo reveals that the initial ejections occurred episodically to produce the concentric shells. This culminated in a vigorous ejection of all of the remaining outer layers, which produced the bright inner regions. At this later stage the ejection was non-spherical, and dense clouds of dust condensed from the ejected material.
Click here to view the Photo Release.
Click here to view the Photo Release.
Last Revised: 08 September 1997