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NASA's Space Place

ISON the Sun Grazer

Alex H. Kasprak
National Aeronautics and Space Administration

There’s a comet barreling toward our sun at breakneck speed. What happens when it gets there is anybody’s guess. Chances are good that it ends up being quite a show, though.

Comet ISON is slowly warming as it hurls itself toward the center of our solar system. As it warms, its icy material is beginning to melt. As it boils off, it turns to gas and sheds dust. This gas and dust creates a bright halo and spectacular tail when lit by the sun. The closer it gets to the sun, the brighter this comet may become.

Comet ISON will be coming so close to the sun that scientists have put it into a special category—sun grazing comets. It passes closest to the sun on November 28th. After that, it could be so bright that it could be seen by the naked eye. It might even be visible during the day!

But the comet will be subjected to a great deal of stress, too. When it passes around the sun it will be traveling almost a million miles an hour and heated to nearly 5,000 degrees Fahrenheit. That could spell disaster for ISON. It’s possible that it could crumble into tiny pieces.

A broken comet could light the sky with multiple glowing bits of comet—a grand spectacle. But it could also fizzle into nothingness. It might just be gobbled up by the sun’s immense heat and gravity.

Chances are, though, that it will hold up. Comets are really hard to predict, but scientists are hopeful that this one sheds a lot of dust and gas. More gas and dust means a brighter comet.

Comet ISON has traveled hundreds of billions of miles to get here. Will its journey come to a dismal end? Will ISON appear triumphant after its trip around the sun? Take a look at the night sky in the coming months and you could find out for yourself!

Want to learn more about comets? Check out “What’s in the heart of a comet” at NASA’s Space Place: http://spaceplace.nasa.gov/comet-nucleus/

Comet ISON imaged by the Hubble Telescope on April 10th 2013 when it was 386 million miles from the sun. Credit: NASA/ESA/J.-Y. Li (PSI)/Hubble Comet ISON Images Science Team.


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