Astronomy Picture Of the Day (APOD)Mercury: A Cratered Inferno
Mercury's surface looks similar to our Moon's. Each is heavily cratered and made of rock. Mercury's diameter is about 4800 km, while the Moon's is slightly less at about 3500 km (compared with about 12,700 km for the Earth). But Mercury is unique in many ways.
The Star Trails of Kilimanjaro
The night had no moon, but the stars were out. And camped at 16,000 feet on Mt. Kilimanjaro, photographer Dan Heller recorded this marvelous 3 1/2 hour long exposure. Here the landscape is lit mostly by the stars.
Cat s Eye
Staring across interstellar space, the alluring Cat's Eye nebula lies three thousand light-years from Earth. A classic planetary nebula, the Cat's Eye (NGC 6543) represents a final, brief yet glorious phase in the life of a sun-like star.
These three bright nebulae are often featured in telescopic tours of the constellation Sagittarius and the view toward the center of our Milky Way galaxy. In fact, 18th century cosmic tourist Charles Messier cataloged two of them; M8, the nebula above and left of center, and colorful M20 at the lower left.
Molecular Torus Surrounds Black Hole
Why do some black hole surroundings appear brighter than others? In the centers of active galaxies, supermassive black holes at least thousands of times the mass of our Sun dominate. Many, called Seyfert Type I, are very bright in visible light. Others, called Seyfert Type II, are rather dim.
A Supernova in Nearby Galaxy NGC 2403
The closest and brightest supernova in over a decade was recorded just over a month ago in the outskirts of nearby galaxy NGC 2403. Officially tagged SN 2004dj, the Type IIP explosion likely annihilated most of a blue supergiant star as central fusion could no longer hold it up.
C153 Takes the Plunge
A comet-like tail of glowing gas, 200,000 light-years long, streams from galaxy C153 as it plunges through galaxy cluster Abell 2125 at nearly 8 million kilometers per hour. Itself a member of the giant cluster of galaxies, C153 may once have been a spiral galaxy like the Milky Way.
M51: The Whirlpool Galaxy in Dust and Stars
The Whirlpool Galaxy is a classic spiral galaxy. At only 30 million light years distant and fully 60 thousand light years across, M51, also known as NGC 5194, is one of the brightest and most picturesque galaxies on the sky.
Looking for water on Mars, researchers using detectors on board the orbiting Mars Odyssey spacecraft have created this false-color global map of energetic neutrons from the otherwise Red Planet. What do neutrons have to do with water?
Hurricane Frances Approaches Florida
A major hurricane is heading for Florida. Hurricane Frances, one of the stronger storm systems of modern times, may cross the eastern coast of Florida sometime tomorrow. Those in the path of a hurricane should take precautions. For example, NASA's Kennedy Space Center has completely shut down.