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Astronomy Picture Of the Day (APOD)
Express to Mars
18.12.2003
Hurtling toward its destination, the high resolution camera on board ESA's Mars Express spacecraft recorded this tantalizing view of the Red Planet earlier this month on December 3rd. Seen from a distance of 5.5 million kilometers, features across part of Mars' western hemisphere are bathed in sunlight.
A Proton Aurora
17.12.2003
What are auroras made out of? Most auroras are caused by the solar wind exciting electrons that are funneled down the Earth's magnetic field. These electrons strike air molecules, liberating other electrons that glow when re-acquired.
Retrograde Mars
16.12.2003
Why would Mars appear to move backwards? Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.
Open Star Clusters M35 and NGC 2158
15.12.2003
Open clusters of stars can be near or far, young or old, and diffuse or compact. Open clusters may contain from 100 to 10,000 stars, all of which formed at nearly the same time. Bright blue stars frequently distinguish younger open clusters.
Close up of the Face on Mars
14.12.2003
Wouldn't it be fun if clouds were turtles? Wouldn't it be fun if the laundry on the bedroom chair was a friendly monster? Wouldn't it be fun if rock mesas on Mars were faces or interplanetary monuments? Clouds, though, are small water droplets, floating on air.
A Flock of Stars
13.12.2003
Only a few stars can be found within ten light-years of our lonely Sun, situated near an outer spiral arm of the Milky Way galaxy. But if the Sun were found within one of our galaxy's star clusters, thousands of stars might occupy a similar space.
Full Moondark
12.12.2003
The brilliant full Moon might not have looked quite like this to skygazers this week, but the image is a mosaic of 18 digital frames recorded on December 9th at 3:30 UT.
Arp 81: 100 Million Years Later
11.12.2003
From planet Earth, we view this strongly interacting pair of galaxies, cataloged as Arp 81, as they were only about 100 million years after their mutual closest approach. The havoc wreaked by gravity during...
Cassini Approaches Saturn
10.12.2003
Cassini, a robot spacecraft launched in 1997 by NASA, is close enough now to resolve many rings and moons of its destination planet: Saturn. The spacecraft has now closed to within a single Earth-Sun separation from the ringed giant. Early last month, Cassini snapped the contrast-enhanced color composite pictured above.
NGC 604: Giant Stellar Nursery
9.12.2003
Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33, a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 was so large, however, it could form enough stars to make a globular cluster.
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