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Astronomy Picture Of the Day (APOD)
Barringer Crater on Earth
11.07.1999
What happens when a meteor hits the ground? Usually nothing much, as most meteors are small, and indentations they make are soon eroded away. 49,000 years ago, however, a large meteor created Barringer Meteor Crater in Arizona, pictured above. Barringer is over a kilometer across.
Southern Neptune
10.07.1999
Neptune, the Solar System's outermost gas giant planet, is 30 times farther from the Sun than Earth. Twelve years after a 1977 launch, Voyager 2 flew by Neptune and found surprising activity on a planet that receives only 3 percent as much sunlight as Jupiter.
NGC 7789: Galactic Star Cluster
9.07.1999
At 1.6 billion years old, this cluster of stars is beginning to show its age. NGC 7789 is an open or galactic star cluster about 8,000 light-years distant toward the constellation Cassiopeia and lies near the plane of our Milky Way galaxy.
Eruptive Prominence
8.07.1999
Activity on our parent star continues to increase as the sun approaches a maximum in its 11-year solar cycle, expected in the year 2000. On June 14 - only a week before the solstice - the space-based SOHO observatory recorded this stunning view of an immense prominence erupting from the sun's southern latitudes (south is up).
M80: A Dense Globular Cluster
7.07.1999
If our Sun were part of M80, the night sky would glow like a jewel box of bright stars. M80, also known as NGC 6093, is one of about 250 globular clusters that survive in our Galaxy.
A Sun Pillar
6.07.1999
Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, stop-sign shaped crystals as it falls from high-level clouds.
Four Faces of Mars
5.07.1999
As Mars rotates, most of its surface becomes visible. During Earth's recent pass between Mars and the Sun, the Hubble Space Telescope was able to capture the most detailed time-lapse pictures ever from the Earth. Dark and light sand and gravel create an unusual blotted appearance for the red planet.
A Landing On Mars
4.07.1999
On July 4th, 1997 - using its own array of fireworks, a parachute, and airbags - the Mars Pathfinder spacecraft successfully came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. Ninety minutes before reaching the surface Pathfinder began a flurry of activity.
NGC 2440: Cocoon of a New White Dwarf
3.07.1999
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!
Shadow Of A Comet
2.07.1999
Hale-Bopp, the Great Comet of 1997, may have been the most viewed comet in history - visible even from bright metropolitan skies. Astronomers are now reporting that this magnificent comet also cast a shadow against the glare of the solar system's ultraviolet haze.
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