Mysterious Disintegrating Asteroid Photographed by Hubble Telescope

For the first time, astronomers have witnessed an asteroid break up into several smaller pieces while it zoomed through space.

This never-before-seen asteroid break-up was recently photographed by the Hubble Space Telescope, the European Space Agency reported Thursday.

The asteroid, known as P/2013 R3, was first spotted in September 2013. Upon further investigation of the asteroid, astronomers realized it was rather peculiar: it consisted of three simultaneous moving bodies embedded in an Earth-sized cloud of dust.

A subsequent investigation with the Hubble revealed the mysterious collection of space rocks was actually 10 distinct objects that are slowly drifting away from each other.

"This is a rock. Seeing it fall apart before our eyes is pretty amazing," said University of California, Los Angeles astronomer David Jewitt, who led the astronomical forensics investigation published in Astrophysical Journal Letters. 

The Hubble observations revealed that the pieces of the asteroid are drifting apart from one another at the rate of 1.5 kilometers per hour, a pace slower than a human's walk. The asteroid became coming apart early last year, the ESA said, noting that the largest of the fragments is 200 meters (656 feet) across.

"This is a really bizarre thing to observe - we've never seen anything like it before," said study co-author Jessica Agarwal of the Max Planck Institute for Solar System Research in Germany. "The break-up could have many different causes, but the Hubble observations are detailed enough that we can actually pinpoint the process responsible."

So far, the astronomers have ruled out that the break-up was caused by collision with an other asteroid (which would have resulted in an instantaneous explosion), and it is unlikely it is breaking up due to the pressure of interior ices warming and vaporizing, the ESA said.

The leading candidate for why the asteroid is breaking up is that the Sun's rays are slowly disintegrating the asteroid, causing its rotation rate to slowly increase over time, leading to its component pieces gradually pulling apart over time due to centrifugal force. This process, known as the YORP effect, has been widely discussed by scientists, but never reliably observed, the ESA reported.

"This is the latest in a line of weird asteroid discoveries, including the active asteroid P/2013 P5, which we found to be spouting six tails," Agarwal said."This indicates that the Sun may play a large role in disintegrating these small Solar System bodies, by putting pressure on them via sunlight."