January 20, 2012
Last summer, on July 6, solar scientist Karel Schrijver spotted something unusual. Looking at a coronagraph—an image created by blocking out the center of the sun, revealing only the corona, the area near its surface—he saw a bright comet, identified as C/2011 N3, descending into the solar atmoshpere. When he searched for the comet on images produced by the Solar Dynamic Observatory (SDO), a solar observation satellite that orbits the earth, he realized he was seeing something unprecedented. For the very first time, the death of a comet crashing into the sun had been caught on camera.
A new paper, published by Schrivjer and a team of scientists today in Science, details the find and what it means for astronomy. Comets dive into the sun frequently, but previous ones had been too small and dim to be seen against the glaring backdrop of the sun. But this comet, an ultra-bright one from a group known as the Kreutz comets, was caught by SDO imaging equipment plunging to its death. Over the course of 20 minutes, it clearly appears descending across the sun before disappearing into its surface. Space.com notes:
“It was very surprising to see this comet at all,” Karel Schrijver, an astrophysicist at Lockheed Martin Advanced Technology Center in Palo Alto, Calif., told SPACE.com. “We may think that an object of some 60,000 metric tons and some 50 meters [164 feet] across is large and heavy, but if you compare it to the sun, which can easily hold a million Earths, it is astonishing that such a small object glows brightly enough to be seen.”
The find, it turns out, is more than merely interesting: It has helped the scientists develop a new method for calculating the size of comets from afar. Using two figures—the amount of time it took the comet to evaporate and the distance over the sun it traveled while doing so—the team figured out its size and speed.
“It was moving along at almost 400 miles per second through the intense heat of the sun—and was literally being evaporated away,” said Schrijver, the lead author of the paper. As the Bad Astronomy blog points out, that speed means it would have crossed the width of the United States in about 8 seconds.
The researchers also estimate that the comet came within 62,000 miles of the sun’s surface before evaporating, and was 70,000 tons in size (about the weight of an aircraft carrier), trailed by a tail 10,000 miles in length.
Some aspects of the discovery, though, are still confusing for the scientists. Most surprising is the fact that we could see the comet at all. Because objects passing in front of the sun absorb light, the comet should have appeared as a dim spot rather than a bright one. Solving this mystery, along with others, might help reveal information about the composition of comets, the sun’s corona and perhaps even the origins of the solar system. Scientists will continue to look to the sun—and scrutinize the data—for answers.
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