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.

2000 July 20
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AR9077: Solar Magnetic Arcade
Credit: TRACE, Stanford-Lockheed ISR, NASA

Explanation: On July 14th, solar active region 9077 (AR9077) produced a massive flare. The event also blasted an enormous cloud of energetic charged particles toward planet Earth, triggering magnetic storms and dramatic auroral displays. This striking close-up of AR9077 was made by the orbiting TRACE satellite shortly after the flare erupted. It shows million degree hot solar plasma cooling down while suspended in an arcade of magnetic loops. The false-color image covers an expansive 230,000 by 170,000 kilometer area on the Sun's surface (Earth's diameter is about 12,800 kilometers) and was recorded in extreme ultraviolet light. Collectively resembling a popular "slinky" toy, the enormous loops are actually magnetic field lines which trap the glowing, cooling plasma above the relatively dark solar surface. After the flare, AR9077's activity decayed as it was carried farther across the Earth-facing hemisphere of the Sun by solar rotation. Active regions like AR9077 appear as groups of dark sunspots in visible light.

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/GSFC
& Michigan Tech. U.