Saturn may be forming a new moon, according to images from the Cassini spacecraft, an orbiter launched to the ringed planet in 1997.
Cassini took the image on April 15, 2013, using its narrow-angle camera. The picture shows a disturbance in Saturn's A ring, which is the outermost of ring in the system. This bulge in the ring is about 750 miles long and 6 miles wide. In the picture, the protuberance is about 20 percent brighter than the ring surrounding it. This formation is consistent with models of satellite formation.
"We have not seen anything like this before. We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right," Carl Murray of Queen Mary University in London and lead author of the accompanying journal article, said.
Saturn's new moon is believed to be just half a mile in diameter so far, too small to be resolved by astronomers. The object has been given the informal name of "Peggy." The object is not likely to get much larger than it is now, according to researchers, and may already be falling apart.
"The discovery image was one of a pair taken 33 [seconds] apart... the feature was apparent in both images, thereby ruling out the possibility of it being a cosmic ray," Murray and his team wrote in the journal article announcing the discovery.
Cassini is expected to approach the area in Saturn's A ring in 2016, providing a possible opportunity to take the first-ever photograph of a moon being born.
Saturn is already known to have at least 53 moons, and astronomers have detected nine other candidate satellites. A general rule-of-thumb holds that the largest satellites of Saturn are orbiting the planet at the greatest distances. This could be the result of the way the earlier moons were created.
"The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons. As the moons formed near the edge, they depleted the rings and evolved, so the ones that formed earliest are the largest and the farthest out," Murray said in a press release from JPL.
By studying formation of the icy body, astronomers hope to learn more about the way moons and planets come into existence around their parent bodies.
Investigation of the possible new moon of Saturn was profiled in the journal Icarus.