"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
Hubble sees asteroid spouting six comet-like tails
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 radiating from it like spokes on a wheel.
Unlike all other known asteroids, which appear simply as tiny points of light, this asteroid, designated P/2013 P5, resembles a rotating lawn sprinkler. Astronomers are puzzled over the asteroid’s unusual appearance.
"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."
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.
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.
Image credit: NASA, ESA, D.Jewitt/UCLA