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.

March 19, 1996

The Ion Tail of Comet Hyakutake
Credit: Oscar Pizarro, 1-meter Schmidt Telescope, La Silla, Chile, European Southern Observatory

Explanation: This picture of Comet Hyakutake was taken on March 14, 1996. Structure in the ion tale of Comet Hyakutake is now clearly visible. An ion tale forms as a comet nears the Sun. Sunlight causes gas and dust to boil off the comet's solid nucleus. Charged gas - called ions - are then accelerated away from the Sun by the solar wind - fast moving particles streaming out from the Sun's corona. The ion tale will appear blue and glows by fluorescence. As Comet Hyakutake gets closer to the Sun during the next month, a dust tail is expected to be visible as well. Dust tails shine by light reflected from the Sun. Comet tails point away from the Sun, even as a comet moves away from the Sun. For observers in the Northern Hemisphere, Comet Hyakutake should appear tonight in the eastern part of the constellation of Virgo and should be about magnitude 2.5. The comet will look the most impressive in the darkest skies - in a city you are likely to see only a fuzzy blob!

Information: The Scale of the Universe Debate in April 1996
Tomorrow's picture: NGC 1977: Blue Reflection Nebula in Orion

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