杏吧原创

The sun鈥檚 atmosphere 鈥� the corona 鈥� is too hot for spacecraft to explore. Luckily, there鈥檚 a family of comets that isn鈥檛 afraid to plunge in, allowing us to probe this mysterious region.

In 2011, one of these sun-grazers, named Lovejoy, became the first comet seen to dive through the sun鈥檚 corona and emerge intact, 鈥� at least for a while (see video). In visible light, the corona is about a millionth as bright as the sun鈥檚 surface, so images of it are usually captured in extreme ultraviolet. In the video above, Lovejoy鈥檚 ice vaporises as it passes through the corona, forming a tail of plasma that shines brightly in extreme UV. Interestingly, the tail moves erratically compared with the comet鈥檚 trajectory.

According to a team led by of Predictive Science in San Diego, California, the wiggling is caused by the sun鈥檚 magnetic field. The researchers are matching the tail鈥檚 motion with computer models of the corona鈥檚 magnetic field, as shown in the video, to explore magnetic activity on the sun.

鈥淲e care about the magnetic field in the corona, because the structure and dynamics of this field dictates the nature of the solar wind and solar eruptions,鈥� says Downs.

The team has applied data obtained from Lovejoy to two competing models of the magnetic field, but it鈥檚 too early for definitive results.

Astronomers are expecting a cluster of sun-grazers to come charging at the sun over the next decade, giving us plenty of opportunities to gather more details. In fact, a large comet called C/2012 S1 (ISON) is expected to come within 1.2 million kilometres of the solar surface this November. 鈥淚f its tail lights up as brightly as Lovejoy鈥檚, the solar encounter could offer a nice probe of the birth region of the solar wind鈥�, says Downs.

Journal reference: , DOI: 10.1126/science.1236550