An enhanced colour view of a raging electrical storm on Saturn taken in 2008.
Credit: NASA
PARIS: A tempest that erupted on Saturn in January has become the Solar System's longest continuously observed lightning storm, say astronomers.
The storm broke out in 'Storm Alley', a region 35º south of the ringed giant's equator, the researchers will tell the European Planetary Science Congress in Potsdam, Germany today.
Thunderstorms there can be as big as 3,000 km across and have lightning bolts 10,000 times as powerful as those on Earth.
Powerful radiowaves
The event was spotted by the NASA space probe Cassini, using an instrument that can detect powerful radiowaves emitted by lightning discharge.
"The reason why we see lightning in this peculiar location is not completely clear," said lead researcher behind the discovery, Georg Fischer of the Austrian Academy of Sciences.
"It could be that this latitude is one of the few places in Saturn's atmosphere that allow large-scale vertical convection of water clouds, which is necessary for thunderstorms to develop."
But another possibility for the southerly location of Storm Alley could be seasonal, he said.
Voyager measurements
In 1980 and 1981, the Voyager spacecraft flew by Saturn and observed lightning storms near the equator.
It could be that the mega-storms will now shift back to equatorial latitudes as Saturn continues its crawl around the Sun. A year in Saturn is equivalent to more than 29 Earth years.
The previous record-breaker for a Solar System thunderstorm was an event that lasted seven and a half months, running from November 2007 to July 2008, also spotted by Cassini.
This is the ninth storm Cassini has tracked since it arrived at Saturn in 2004.
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