Giant ring system surrounds distant planet

Artist's impression of the massive ring system circling the young giant gas planet J1407B.
Ron Miller
A ring system roughly 200 times larger than the rings of Saturn has been analysed by astronomers at the Leiden Observatory, The Netherlands, and the University of Rochester in the US.

The rings surround a young giant gas planet or brown dwarf star denoted as J1407b. "This planet is much larger than Jupiter or Saturn, and its ring system is roughly 200 times larger than Saturn's rings are today," says Eric Mamajek, professor of physics and astronomy at the University of Rochester.

Matthew Kenworthy from Leiden who led the study, says J1407b is too far away to observe directly. "We could make a detailed model based on the rapid brightness variations in the star light passing through the ring system," he says. "If we could replace Saturn's rings with the rings around J1407b they would be easily visible at night and many times larger than the full moon."

The astronomers have calculated that the diameter of the ring system is almost 120 million kilometres and that their mass is roughly equal to the Earth.

"The planetary science community has theorised for decades that planets like Jupiter and Saturn would have had, at an early stage, disks around them that then led to the formation of satellites," says Mamajek. "However until we discovered this object in 2012, no one had seen such a ring system. This is the first snapshot of satellite formation on million-kilometre scales around a sub-stellar object."

Astronomers believe the rings will become thinner over the next several million years, and may eventually disappear as satellites form out of the disks.

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