That's why astronomers weren't sure what would happen in early March when Comet Pan-STARRS, a first-time visitor to the inner solar system, dipped inside the orbit of Mercury. On March 10th, NASA’s STEREO-B spacecraft watched as the comet made its closest approach to the sun only 28 million miles away. At that distance, the sun loomed 3 times wider and felt more than 10 times hotter than it does on Earth.
The comet survived.
A new ScienceCast video tracks the progress of Comet Pan-STARRS and the development of its wild tail. Play it
Now we know. "It is a gorgeous comet--one of the brightest in years," says astronomer Matthew Knight of the Lowell Observatory.
NASA's STEREO-B spacecraft photographed "wild striations" in the tail of Comet Pan-STARRS as it passed by the sun. Play the movie
The amount of dust and gas spewing from the comet implies a nucleus on the order of 1 km in diameter--in other words, neither unusually large nor small. Size-wise, it is a fairly typical comet.
The comet’s tail is anything but typical. STEREO-B images processed by Karl Battams of the Naval Research Lab in Washington DC reveal many wild and ragged striations in the cloud of dust trailing behind Pan-STARRS. "Wow!" says Battams. "The fine-structure is breathtaking. We think this is caused by some fairly complex interaction between the solar wind and the comet's rotating nucleus. It's going to take computer models to figure this one out."
The comet is now receding from Earth. It will slowly dim as it heads back into deep space. Ironically, though, its visibility will improve for a while as it heads into darker skies away from the sun. In the last weeks of March it could become an easy naked-eye object.
Step outside after sunset, face west, and take a look.
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