Birth of a baby moon on Saturn?

Astronomers believe that they might have just witnessed the birth of a baby moon for the first time as NASA's Saturn-orbiting Cassini spacecraft has imaged something peculiar on the outermost edge of the gas giant's A-ring.

They spotted a bright knot, or arc, 20 percent brighter than the surrounding ring material and astronomers are interpreting it as a gravitational disturbance caused by a tiny moon.

"We have not seen anything like this before," said Carl Murray of Queen Mary University of London.

"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," Murray added.

The feature in the ring's edge is approximately 1,200 km long and 10 km wide but the possible baby moon is likely only half a mile across if it has confirmed to exist.

The discovery was announced in the journal Icarus.