Space

Hubble Spots Odd Asteroid With Six Tails

November 8, 2013 | by Lisa Winter

Photo credit: NASA, ESA, and D. Jewitt (UCLA)

Silly asteroid, tails are for comets! Around five months ago, an asteroid called P/2013 P5 was seen to be kicking off dust, making it look like it had a tail like a comet. Use of more detailed imaging would show that the asteroid actually has an unprecedented six tails.

In August, researchers had noticed P/2013 P5, an asteroid with a nucleus 1400 feet (427 meters) long, looked somewhat blurred through the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS). Traditionally, asteroids appear as a sharp point of light, and this anomaly piqued the curiosity of the researchers. They figured that it might have begun rotating extremely quickly, causing it to kick off some of its surface dust and look like a comet. 

On September 10, the team used the Hubble Space Telescope to get more detailed images of the oddball asteroid. The results completely dumbfounded the researchers: the asteroid had six tails that jut out in all directions, like spokes on a bicycle wheel! Even more amazing was the fact that when the team looked at it again less than two weeks later, the tails looked completely different. 

After extensive analysis, it was determined that the tails are most likely the byproducts from six different dust-ejection events that were pulled out like tails by solar radiation pressure. That pressure is also believed to be what caused the asteroid to begin spinning so quickly in the first place, in a phenomenon known as radiation torque. If an asteroid is spinning too fast, its small amount of gravity is not enough to hold itself together and the dust goes flying off. Because the dust pattern does not suggest that a lot of material was ejected from the asteroid at once, the researchers are currently discounting the idea that these tails are the products of a collision. The results were published in Astrophysical Journal Letters.

So far, only a small percentage of its mass has been sloughed off into the tails, but this could be the beginning of the end for the asteroid. Future analysis will show if the dust is being ejected around the asteroid's equator, which will be the best evidence that the asteroid is in the process of a rotational breakup. 

While this is the first six-tailed asteroid that has ever been documented, researchers are confident that if there is one, there are probably many more waiting to be discovered. 

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