Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

June 10, 1996

Ultraviolet Earth
Credit: NASA, Apollo 16, George Carruthers (NRL) and the Far UV Camera Team

Explanation: Here's a switch: the above picture is of the Earth taken from a lunar observatory! This false color picture shows how the Earth glows in ultraviolet (UV) light. UV light is so blue humans can't see it. Very little UV light is transmitted through the Earth's atmosphere but what sunlight does make it through can cause a sunburn. The Far UV Camera / Spectrograph deployed and left on the Moon by the crew of Apollo 16 took the above picture. The part of the Earth facing the Sun reflects much UV light, but perhaps more interesting is the side facing away from the Sun. Here bands of UV emission are also apparent. These bands are the result of aurora and are caused by charged particles expelled by the Sun spiraling to Earth along magnetic field lines.

Tomorrow's picture: Doomed Star Eta Carinae

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Authors & editors: Robert Nemiroff (GMU) & Jerry Bonnell (USRA).
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