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 24, 1996

Comet Hyakutake's Closest Approach
Credit and Copyright: Herman Mikuz, Crni Vrh Observatory, Slovenia

Explanation: The above true colour image of Comet Hyakutake was taken the night of March 21/22. Tonight, Comet Hyakutake will make its nearest approach to Earth, closing to a mere 10 million miles as it passes over the planet's Northern Hemisphere. From dark sky areas, it's tail may be seen to cover about 20 degrees on the sky (40 times the apparent diameter of the full moon) corresponding to well over 3 million miles. at the distance of the comet. The word comet, referring to the tail, derives from the Greek "aster kometes", meaning long-haired star - and the hair of comet Hyakutake continues to grow as it nears the Sun! The tail grows as the sun heats and sublimates (changes directly from solid to gas) the material on the icy surface of the comet nucleus, sending jets of gas and dust into space. The material is swept back by the solar wind, so comet tails usually point away from the sun rather than simply trailing along behind in the comets' orbit. Some predict the tail will grow over the next few days to nearly 50 degrees. For the rest of March and most of April Comet Hyakutake will be visible to Northern viewers (weather permitting). The tail will be most visible from dark sky areas. Moonlit skies will tend to washout the comet as the April 3rd full moon approaches - however, on April 3rd, there will be a lunar eclipse!

Tomorrow's picture: Comet Hyakutake Passes the Earth

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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.