Solar hurricane rips off comet's tail

Flaming comet
NASA said today one of its satellites captured the image of a solar hurricane ripping off the tail of a passing comet. The resulting collision saw the complete detachment of the plasma tail of Encke's comet, which was traveling within the orbit of Mercury, NASA said.

The comet is only the second repeating, or periodic, comet ever identified and has the shortest orbital period - about 3.3 years - of any known comet. Halley's comet was the first.

Solar hurricanes or "coronal mass ejections" are large clouds of magnetized gas blown into space by the sun. They are violent eruptions with masses upwards of a few billion tons traveling anywhere from 100 to 3,000 kilometers per second (62 to 1,864 miles/second). They have been compared to hurricanes because of the widespread disruption they can bring when directed at Earth; such activities are known to cause geomagnetic storms that can present hazards for satellites, radio communications, and power systems.

In a release, NASA said preliminary analysis suggests that the tail was ripped away when magnetic fields bumped together in an explosive process called "magnetic reconnection." Oppositely directed magnetic fields around the comet "bumped into each" by the magnetic fields in the hurricane. Suddenly, these fields linked together--they "reconnected"--releasing a burst of energy that tore off the comet's tail. A similar process takes place in Earth's magnetosphere during geomagnetic storms fueling, among other things, the Northern Lights, NASA said.

The results are published online today in the Astrophysical Journal Letters Rapid Release website and in the October 10 print issue of the journal. For some pictures of the event go here.

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