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Astronomy Picture Of the Day (APOD)
Degas Ray Crater on Mercury
8.12.1996
Like the Earth's Moon, Mercury is scarred with craters, testifying to an intense bombardment during the early history of the Solar System. In 1974, the Mariner 10 spacecraft surveyed this innermost planet up close, producing the only detailed images of its tortured surface.
Planetary Systems Now Forming in Orion
7.12.1996
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.
Globular Cluster M3
6.12.1996
This huge ball of stars predates our Sun. Long before mankind evolved, before dinosaurs roamed, and even before our Earth existed, ancient globs of stars condensed and orbited a young Milky Way Galaxy.
Io's Giant Volcano Pele
5.12.1996
Io has some very large volcanoes. One of the largest is evident near the center of the above photograph and named Pele, for the mythological Polynesian fire goddess. The Galileo spacecraft now orbiting Jupiter took this picture of Jupiter's most active moon in June, although it was released just last week.
Ice at the Lunar South Pole
4.12.1996
Ice on the Moon? The prospecting Clementine spacecraft may well have discovered it. In 1994, Clementine spent 70 days in lunar orbit mapping the Moon's surface. Shown above is a dramatically detailed composite view centered on the Lunar South Pole - constructed from 1500 Clementine images.
Cocoon of a New White Dwarf
3.12.1996
Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all!
Orion's Star Colors
2.12.1996
What determines a star's color? Its temperature. Red stars are cool, with temperatures of around 3,000 degrees Kelvin (K), while blue stars are hotter and can have temperatures over 30,000 degrees K. Our own lovely yellow Sun's temperature is a comforting 6,000 degrees K.
Star Trails in Northern Skies
1.12.1996
As the Earth spins on its axis, the sky seems to rotate around us. This motion produces the beautiful concentric arcs traced out by the stars in this time exposure of the night sky.
Aurora Astern
30.11.1996
Sailing upside down, 115 nautical miles above Earth, the crew of the Space Shuttle Endeavour made this spectacular time exposure of the southern aurora (aurora australis) in October of 1994. The aurora, also known...
Io: The Fissure King?
29.11.1996
Is Io the solar system's Fissure King? Well, probably not ... but it is the most active volcanic moon. Active volcanoes on Jupiter's moon Io were a surprise discovery of the Voyager missions of the late 1970s.
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