Photo in the News: Comet Loses Tail in Space Collision

Alt tag: picture of comet tail
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October 3, 2007—For the first time, scientists have witnessed a collision between a comet and a solar hurricane.

The intergalactic crash—recorded by a NASA Solar Terrestrial Relations Observatory satellite on April 20—sliced off the Encke comet's plasma tail as it was traveling within Mercury's orbit.

[See still taken from an animation sequence (top) and satellite images (below).]

"We were awestruck when we first saw these images," Angelos Vourlidas, lead author of a new study on the event and researcher at the Naval Research Laboratory, said in a statement.

"The surprise of seeing the disconnection of the tail was just the icing on the cake."

Comets usually have two tails, one made of dust and a fainter one made of electrically conducting gas called plasma. The Encke comet is periodic, meaning it passes near the sun on a set interval.

Solar hurricanes—or coronal mass ejections—occur when the sun spews out fierce eruptions of magnetized gas. The ejections create geomagnetic storms that can wreak havoc on human-made satellites and communication systems.

Though scientists suspected solar hurricanes could be responsible for comets losing their tails, no one had been sure—until now.

Early analyses of the collision suggest that the comet lost its tail through a process called magnetic reconnection, when a comet's magnetic field is "crunched" by those of the solar hurricane. The comet's fields then reconnect, sparking a burst of energy that lops off its tail.

The study will appear in the October 10 print edition of Astrophysical Journal Letters.

—Christine Dell'Amore

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