London, June 19 : A new study has suggested that a new type of aurora may exist on Saturn, creating a faint ring around one the planet's poles.
According to a report in New Scientist, the planet has oval-like auroras that periodically brighten its poles. Its main auroras are thought to be caused by the solar wind.
This type of aurora is thought to be much like the Earth's, which is caused by the solar wind, a stream of charged particles emanating from the Sun.
When the solar wind crosses paths with the magnetic fields of the planets, intermittent fireworks light up the skies around the poles.
But now, astronomers say Saturn may also exhibit a dimmer, continuous type of aurora.
Its source may be similar to that on Jupiter, where the volcanic moon Io, along with several other moons, spews roughly a tonne of material per second into orbit around the gas giant.
"We've been able to find an aurora that seems to be very similar to Jupiter's," said Tom Stallard, a planetary astronomer at the University of Leicester in the UK.
On Saturn, the source is thought to be the moon Enceladus, which sloughs off an estimated 100 kilograms of material per second into orbit around Saturn via plumes of water vapour first discovered in 2005.
"The recent detection of volcanic plumes on Enceladus suggests that's probably the dominant source," Stallard told New Scientist.
Saturn's secondary auroral ring is too faint to see. To spot it, Stallard and colleagues used a ground-based instrument to look at infrared light near Saturn's south pole.
There, they found that the glow of charged particles extended beyond the planet's main auroral oval.
According to the researchers, the material feeding the secondary auroras might be coming off Saturn's rings, though they believe the more likely culprit is Enceladus.
The connection would be made plain if astronomers could find some direct evidence of interaction between Enceladus and Saturn's magnetic field.
The discovery fills out a picture of how auroras form on planets with strong magnetic fields.
"This paper is a contribution that shows that Saturn does have some auroral processes that are like Jupiter," said John Clarke of Boston University, US. "Further studies could contribute to models of how such auroras might form on extrasolar planets," he added.