Scientists discovered a comet just inside Neptune. It was estimated that it was between 62 and 125 miles long. This would be the largest comet ever found if the estimates were correct.
The comet nucleus was measured with precision by the Hubble Space Telescope in January because scientists wanted to be certain that the term stuck. The comet's core could be up to 85 miles wide, making it more than twice the width of Rhode Island. It has a mass of 500 trillion tons, which is equivalent to 2,800 Mount Everests.
David Jewitt, an astronomer and planetary scientist at the University of California, Los Angeles, said that it was 100 times bigger than the typical comet.
The comet will be visible to the naked eye for a short time. It is traveling at a rate of 22,000 miles per hour. It will appear as a faint glow in the night sky in 2031, when it will only get within a billion miles of the sun.
Astronomers can see and study this extraterrestrial visitor in all its glory, almost as if they were flying right beside it, thanks to the help of Hubble.
It was difficult to measure the size of the comet's nucleus. Although far from the sun, just a trickle of sunlight is enough to create an obfuscating dusty atmosphere known as a coma.
The comet nucleus could not be clearly seen by Hubble. Dr. Jewitt and his colleagues were able to make a computer model of the coma by taking high-resolution images of the comet. It was easy to size it up with only the nucleus remaining.
Their analysis showed that the nucleus is blacker than coal. Dr. Jewitt said that this may be caused by being cooked by cosmic rays. Cosmic rays have broken the chemical bonds on the nucleus. The lighter elements were able to escape into space and leave behind dark-colored carbon, which made the nucleus a bit like a slice of toast.
Teddy Kareta, a planetary scientist, said that comet nuclei are always superdark. He suggests comparing comets to a pile of snow.
The comet will reveal more of its secrets as it approaches the planet. As it begins the return leg of its three-million-year circuit of the sun in 2031, there won't be much to know about its origin.
There is a sneak preview of what is inside that bubble. It is a reminder of how little we know about the outer solar system.
Who knows what's going on out there?
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