Video: Close Call in the Corona

Credit: Video courtesy of Cooper Downs

Deep inside the sun's atmosphere, temperatures reach millions of degrees—so hot that even the best-shielded spacecraft can't go there (even at night). But natural objects that pass exceptionally close to the sun do provide scientists opportunities to directly probe the solar corona. Enter sun-grazing comets, such as comet Lovejoy, which whizzed within 140,000 kilometers of the sun's surface in mid-December 2011 (as seen in the first 20 seconds of the video). When a comet is far from the sun, its tail acts like a weather vane in the solar wind (the torrent of charged particles that streams outward from the sun's upper atmosphere). But observations made from multiple angles by three different craft revealed that comet Lovejoy's tail waggled and wobbled in unexpected ways (see video, from 0:20 onward) as the object zipped through the deepest parts of the solar atmosphere. Those motions provide direct insight into the intense, highly variable magnetic fields close to the sun, the researchers report online today in Science. That, in turn, allows solar physicists to tweak their models of the corona and the processes that take place there, including how the solar wind forms and how it is accelerated to incredibly high speeds. Comet Lovejoy was the first sun-grazer known to survive its approach and reemerge from the corona, the researchers note. But alas, future sightings of this object probably aren't in the cards: Less than a week after the comet swooped past the sun, its icy nucleus shattered and disappeared, likely due to its brief but close call with extreme heat.

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