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Astronomy Picture Of the Day (APOD)
Layered Hills on Mars
24.12.2003
Why are some hills on Mars so layered? The answer is still under investigation. Clearly, dark windblown sand surrounds outcropping of light sedimentary rock across the floor of crater Arabia Terra. The light rock clearly appears structured into many layers, the lowest of which is likely very old.
Comet Encke Returns
23.12.2003
It's back. Every 3.3 years, Comet Encke swoops back into our inner Solar System. First officially discovered in 1786, Comet Encke is on its 59 th documented return, making it one of the best-studied comets on the sky.
The Andromeda Galaxy from GALEX
22.12.2003
Why does the Andromeda Galaxy have a giant ring? Viewed in ultraviolet light, the closet major galaxy to our Milky Way Galaxy looks more like a ring galaxy than a spiral. The ring...
N159 and the Papillon Nebula
21.12.2003
In a search for massive stars, the Hubble Space Telescope has peered into yet another spectacular region of star formation. This nebula, known as N159, spans over 150 light-years and is located in the neighboring Large Magellanic Cloud galaxy, about 170,000 light years distant.
The Flight of Helios
20.12.2003
An example of solar-powered flight, NASA's Helios aircraft flew almost one hundred years after the Wright brothers' historic flight on December 17, 1903. Pictured here at 10,000 feet in in skies northwest of Kauai, Hawaii in August 2001, the remotely piloted Helios is traveling at about 25 miles per hour.
Inside The Elephant s Trunk
19.12.2003
Spectacular first images from the newly christened Spitzer Space Telescope include this penetrating interior view of an otherwise opaque dark globule known as the Elephant's Trunk Nebula. Seen in a composite of infrared...
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.
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