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Astronomy Picture Of the Day (APOD)
The Yardangs Of Mars
13.11.2000
OK, fans of classic science fiction might be disappointed. The yardangs are not barsoomian warriors in a newly discovered Edgar Rice Burroughs tale of adventure and conquest on the Red Planet. In fact yardangs, geologists' term for narrow, wind-eroded ridges, are common land features in the desert regions of planet Earth.
Disorder in Stephan's Quintet
12.11.2000
What are four closely grouped galaxies doing in this image? The grouping composes a majority of the large galaxies in Stephan's Quintet, with the fifth prominent galaxy located off the above image to the lower right.
The Lyman Alpha Forest
11.11.2000
We live in a forest. Strewn throughout the universe are "trees" of hydrogen gas that absorb light from distant objects. These gas clouds leave numerous absorption lines in a distant quasar's spectra, together called the Lyman-alpha forest.
The First Lunar Observatory
10.11.2000
The first, and so far only, lunar astronomical observatory was deployed by the Apollo 16 crew in 1972. The Far Ultraviolet Camera / Spectrograph used a 3-inch diameter Schmidt telescope to photograph the Earth, nebulae, star clusters, and the Large Magellanic Cloud.
X Ray Cygnus A
9.11.2000
Amazingly detailed, this false-color x-ray image is centered on the galaxy Cygnus A. Recorded by the orbiting Chandra Observatory, Cygnus A is seen here as a spectacular high energy x-ray source. But it is actually more famous at the low energy end of the electromagnetic spectrum as one of the brightest celestial radio sources.
The Cosmic X-Ray Background
8.11.2000
Early on, x-ray satellites revealed a surprising cosmic background glow of x-rays and astronomers have struggled to understand its origin. Now, peering through a hole in the obscuring gas and dust...
October Skylights
7.11.2000
With brilliant Venus above the western horizon at sunset and Jupiter and Saturn high in the east by early evening, November's night sky is filled with bright planets. October's sky featured bright planets as well and, triggered by the active Sun, some lovely auroral displays.
The Gum Nebula Supernova Remnant
6.11.2000
Because the Gum Nebula is the closest supernova remnant, it is actually hard to see. Spanning 40 degrees across the sky, the nebula is so large and faint it is easily lost in the din of a bright and complex background.
Heaven on Earth
5.11.2000
If sometimes it appears that the entire Milky Way Galaxy is raining down on your head, do not despair. It happens twice a day. As the Sun rises in the East, wonders of the night sky become less bright than the sunlight scattered by our own Earth's atmosphere, and so fade from view.
Jupiter Swallows Comet Shoemaker Levy 9
4.11.2000
What happens when a comet encounters a planet? If the planet has a rocky surface, a huge impact feature will form. A giant planet like Jupiter, however, is mostly gas. When Comet Shoemaker-Levy 9 struck Jupiter in 1994, each piece was swallowed into the vast Jovian atmosphere.
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