text: The Hubble space telescope sure has seen some strange things in deep space, but this most recent find is possibly one of the strangest. Introducing the six-tailed comet… or is it an asteroid? Or some kind of weird alien sprinkler system in the asteroid belt? 
   
   The object — called P/2013 P5 — was discovered in August by the Pan-STARRS 1 telescope in Hawaii, an observation that baffled astronomers. All they could see was a nondescript fuzzy blob. So, employing the help of Hubble, the space telescope slewed around and observed the mystery object twice in September. What it saw was something just as baffling as what Pan-STARRS astronomers originally described: it was a weird multi-tailed comet-like object. Or so it appeared. 
   
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   Apart from the fact that P5 appears to have jets of gas and dust projecting in all directions — like spokes on a bicycle wheel — between the Sept. 10 and Sept. 23, “the entire structure had swung around,” writes a Hubble science news release. This is all very un-comet-like — and, indeed, un-asteroid-like — behavior. 
   
   “We were literally dumbfounded when we saw it,” said David Jewitt, lead investigator from the University of California at Los Angeles. “Even more amazingly, its tail structures change dramatically in just 13 days as it belches out dust. That also caught us by surprise. It’s hard to believe we’re looking at an asteroid.” 
   
   So what is it? Needless to say, there are theories. 
   
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   The asteroid belt, that is located between the orbits of Mars and Jupiter, is home to a huge population of asteroids. Asteroids are known to be affected by the sun’s radiation — like their cometary cousins, they heat up. But given enough time, asteroids can undergo what is known as the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect. 
   
   The uneven heating on an asteroid’s surface can cause it to “spin up.” In a nutshell, the YORP effect heats up the sun-facing side of an asteroid, but as the asteroid rotates, it radiates heat into space from the dark side. This heat radiation is carried away by infrared photons that themselves exert a tiny amount of momentum, or recoil, as they depart the asteroid. Over long periods (thousands to millions of years), this radiation acts to speed up an asteroid’s spin. 
   
   But what of P5? Could the YORP effect explain these strange spoke features? 
   
   Jessica Agarwal of the Max Planck Institute for Solar System Research in Lindau, Germany, modeled a spinning asteroid to show the tails may be caused by impulsive dust-ejection events. Basically, we could be witnessing an asteroid that has been “spun up” at such a high rate by the sun that it is starting to lose integrity — centrifugal forces are causing it to eject dusty jets into space. “Given our observations and modelling, we infer that P/2013 P5 might be losing dust as it rotates at high speed,” said Agarwal. “The sun then drags this dust into the distinct tails we’re seeing.” 
   
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   The space rock, which measures up to 240 meters wide, has probably only lost about 100-1000 tons of dust — a tiny fraction of its total mass. Although the spinning jets of dust seems the most likely explanation, follow-up observations are needed to see if the jets are being emitted in a plane, from the asteroid’s equator. 
   
   “In astronomy, where you find one, you eventually find a whole bunch more,” said Jewitt. “This is just an amazing object to us, and almost certainly the first of many more to come.” 
   
   Jewitt’s team has published a paper describing this fascinating object in the Nov. 7 issue of The Astrophysical Journal Letters (doi:10.1088/2041-8205/778/1/L21). 
   
   Image: Left: A Hubble observation of P/2013 P5 exhibiting the spoke-like dusty jets. Right: Diagram showing the spinning asteroid generating the jets. Credits: NASA, ESA, D. Jewitt (University of California, Los Angeles), J. Agarwal (Max Planck Institute for Solar System Research), H. Weaver (Johns Hopkins University Applied Physics Laboratory), M. Mutchler (STScI), and S. Larson (University of Arizona) ||||| 
   
   Nov. 7, 2013: Astronomers viewing our solar system's asteroid belt with NASA's Hubble Space Telescope have seen for the first time an asteroid with six comet-like tails of dust. Designated P/2013 P5, the asteroid resembles a rotating lawn sprinkler. 
   
   "We were literally dumbfounded when we saw it," said lead investigator David Jewitt of the University of California at Los Angeles. "Even more amazing, its tail structures change dramatically in just 13 days as it belches out dust. That also caught us by surprise. It's hard to believe we’re looking at an asteroid." 
   
   This NASA Hubble Space Telescope set of images reveals a never-before-seen set of six comet-like tails radiating from a body in the asteroid belt, designated P/2013 P5. 
   
   Jewitt leads a team whose research paper appears online in the Nov. 7 issue of the Astrophysical Journal Letters. 
   
   P/2013 P5 has been ejecting dust periodically for at least five months. Astronomers believe it is possible the asteroid's rotation rate increased to the point where its surface started flying apart. They do not believe the tails are the result of an impact with another asteroid because they have not seen a large quantity of dust blasted into space all at once. 
   
   Scientists using the Pan-STARRS survey telescope in Hawaii announced their discovery of the asteroid Aug. 27. P/2013 P5 appeared as an unusually fuzzy-looking object. The multiple tails were discovered when Hubble was used to take a more detailed image Sept. 10. 
   
   When Hubble looked at the asteroid again Sept. 23, its appearance had totally changed. It looked as if the entire structure had swung around. 
   
   "We were completely knocked out," Jewitt said. 
   
   Careful modeling by team member Jessica Agarwal of the Max Planck Institute for Solar System Research in Lindau, Germany, showed that the tails could have been formed by a series of impulsive dust-ejection events. She calculated that dust-ejection events occurred April 15, July 18, July 24, Aug. 8, Aug. 26 and Sept. 4. Radiation pressure from the sun stretched the dust into streamers. 
   
   Radiation pressure could have spun P/2013 P5 up. Jewitt said the spin rate could have increased enough that the asteroid's weak gravity no longer could hold it together. If that happened, dust could slide toward the asteroid's equator, shatter and fall off, and drift into space to make a tail. So far, only about 100 to 1,000 tons of dust, a small fraction of the P/2013 P5's main mass, has been lost. The asteroid's nucleus, which measures 1,400 feet wide, is thousands of times more massive than the observed amount of ejected dust. 
   
   Astronomers will continue observing P/2013 P5 to see whether the dust leaves the asteroid in the equatorial plane. If it does, this would be strong evidence for a rotational breakup. Jewitt's interpretation implies that rotational breakup must be a common phenomenon in the asteroid belt. It might even be the main way small asteroids die. 
   
   "In astronomy, where you find one, you eventually find a whole bunch more," Jewitt said. "This is just an amazing object to us, and almost certainly the first of many more to come." 
   
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   Production editor: Dr. Tony Phillips | Credit: Science@NASA 
   
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   Jewitt said it appears P/2013 P5 is a fragment of a larger asteroid that broke apart in a collision roughly 200 million years ago. There are many collision fragments in orbits similar to P/2013 P5's. Meteorites from these bodies show evidence of having been heated to as much as 1,500 degrees Fahrenheit. This means the asteroid likely is composed of metamorphic rocks and does not hold any ice as a comet does.
target: – The Hubble telescope has spotted a spectacular, perplexing object in the middle of the Asteroid Belt: a rock with six "comet-like" dust tails streaming behind it. "We were literally dumbfounded when we saw it," David Jewitt, the head of the astronomy team studying the P/2013 P5, said in a NASA release. "Even more amazing, its tail structures change dramatically in just 13 days as it belches out dust. That also caught us by surprise. It's hard to believe we're seeing an asteroid." The team hypothesizes that the sun's radiation set the 260-yard-wide rock spinning—thanks, Discovery explains, to the Yarkovsky-O'Keefe-Radzievskii-Paddack effect—so quickly that it lost structural integrity. Using modeling, one team member calculated six dates when the asteroid likely ejected dust into space. So far, it has likely ejected as much as 1,000 tons of dust into space, but that's still a tiny fraction of its mass. "This is just an amazing object to us, and almost certainly the first of many," Jewitt says. "In astronomy, when you find one, you eventually find a whole bunch more."