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.

2003 December 3
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Moonrise Through Mauna Kea's Shadow
Credit & Copyright: Michael Connelley (U. Hawaii)

Explanation: How can the Moon rise through a mountain? It cannot -- what was photographed here is a moonrise through the shadow of a large volcano. The volcano is Mauna Kea, Hawai'i, USA, a frequent spot for spectacular photographs since it is arguably the premier observing location on planet Earth. The Sun has just set in the opposite direction, behind the camera. Additionally, the Moon has just passed full phase -- were it precisely at full phase it would rise, possibly eclipsed, at the very peak of the shadow. Refraction of moonlight through the Earth's atmosphere makes the Moon appear slightly oval. Cinder cones from old volcanic eruptions are visible in the foreground. Cloud tops below Mauna Kea's summit have unusually flat tops, indicating a decrease in air moisture that frequently keeps the air unusually dry, another attribute of this stellar observing site.

Tomorrow's picture: New Horizons

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