September 29, 1996
The Earth has carried you around the Sun again, steady as ever, while the stars kept their patient watch.
The X-Ray Moon Credit:
Birthday · September 29, 1996
A little universe, just for you
Your date.
Ready to give.
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APOD published September 29, 1996. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
This X-Ray image of the Moon was made by the orbiting Roentgen Observatory Satellite (ROSAT) in 1990. It shows three distinct regions: a bright X-ray sky, a bright part of the Moon, and a relatively dark part of the Moon. The bright X-ray sky is due to the diffuse cosmic X-ray background. The bright lunar crescent shines because it reflects X-rays emitted by the Sun. The dark lunar face is in shadow and so stands stands out from the relatively bright background - but, surprisingly it is not completely dark! Where do those X-rays from? They are currently thought to result from energetic particles from the solar wind bombarding the lunar surface.