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Astronomy Picture Of the Day (APOD)
Magnetic Mars
4.05.1999
Mapping Mars from orbit, instruments on the Mars Global Surveyor (MGS) spacecraft have recently revealed banded magnetic field patterns - a startling and unanticipated suggestion that the Red Planet was more Earth-like in its distant past.
Loop I in the Northern Sky
3.05.1999
One of the largest coherent structures on the sky is known simply as Loop I and can best be seen in radio and X-ray maps. Spanning over 100 degrees, part of Loop I appears so prominent in northern sky maps that it is known as the North Polar Spur (NPS).
Stars from Eagles Eggs
2.05.1999
Newborn stars are forming in the Eagle Nebula. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars.
Lunar Dust and Duct Tape
1.05.1999
Why is the Moon dusty? On Earth, rocks are weathered by wind and water, creating soil and sand. On the Moon, the long history of micrometeorite bombardment has blasted away at the rocky surface creating a layer of powdery lunar soil or regolith. This lunar regolith could be a scientific and industrial bonanza.
Solar Shock Wave
30.04.1999
On September 24, 1997 a shock wave blasted across the surface of the sun at speeds of 250 to 600 kilometers per second. On planet Earth, observer Barry Reynolds photographed the expanding shock front (left) in the light emitted by hydrogen atoms at the solar surface.
NGC 2266: Old Cluster in the New General Catalog
29.04.1999
The New General Catalog of star clusters and nebulae really isn't so new. In fact, it was published in 1888 - an attempt by J. L. E. Dreyer to consolidate the work of astronomers William, Caroline, and John Herschel along with others into a useful single, complete catalog of astronomical discoveries and measurements.
A Sundial for Mars
28.04.1999
When Mars Surveyor arrives at Mars in 2002, it will carry a sundial. Even though batteries and a solar array will power the Mars Surveyor Lander, the sundial has been included to allow a prominent public display of time.
Introducing Comet Lee
27.04.1999
Another large snowball is falling toward the Sun. Comet Lee was discovered two weeks ago by Steve Lee (AAO) in Australia, and is expected to brighten as it approaches the inner Solar System. Comet...
USNO A2.0 Catalog: A Digital Sky
26.04.1999
Here lie 526,230,881 of the brightest stars known. The US Naval Observatory has deployed their monster Precision Measuring Machine to digitize photographic plates covering the whole sky and creating the above map. Yellow corresponds to 150,000 stars per square degree, while dark blue corresponds to only 500 stars per square degree.
Mimas: Small Moon with a Big Crater
25.04.1999
Mimas is one of the smaller moons of Saturn but shows one of the largest impact craters. In fact, if the impact had been much greater, it would have disrupted the entire satellite. The large crater has been named Herschel after the 1789 discoverer of Mimas, Sir William Herschel.
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