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Superflares found on Sun-like stars

Artistic rendition of a "superflare star".

Artistic rendition of a 'superflare star'. It has large starspots - much larger than those on the Sun - and a superflare (white region) occuring near the starspots (Source: Hiroyuki Maehara/Kwasan and Hida Observatories, Graduate School of Science, Kyoto University)

Super storms Scientists have found superflares more than 1 million times more powerful than flares generated by the Sun occurring on stars being studied by NASA's Kepler space telescope.

The finding, published in the journal Nature, culled from 120 days of observations of 83,000 stars, is the first to detail how often and how energetic flares on other stars can be.

The discovery, however, raises a question about how the massive outbursts, believed to be caused by complex magnetic interactions, can physically occur.

Scientists previously theorised a close-flying Jupiter-sized planet would be needed to ground a super-flaring stars' magnetic fits. For the size flares our Sun experiences, magnetic reconnection occurs within the Sun itself, with one twisted magnetic field snapping and then linking up to another - releasing energy in the process as a solar flare.

But the 365 superflares found by scientists crunching Kepler data need another explanation, says astrophysicist Bradley Schaefer, of Louisiana State University.

Kepler, whose prime mission is to look for planets transiting the face of their parent stars, should have found big, close-by planets (so-called "hot-Jupiters") circling about 10 per cent of the superflaring stars. Instead the team, led by Kyoto University astronomer Hiroyuki Maehara, found none.

"Maehara's point that the 365 superflares don't show hot-Jupiters is a pretty strong argument against the hot-Jupiter theory," says Schaefer. "No one has proposed any alternative."

Maehara thinks they could be caused by starspots much larger than any sunspot found on the sun.

"However it is not well understood why and how such large starspots are formed on solar-type stars," he says.

"This very much is a mystery and a challenge for classic astrophysics," says Schaefer.

Scientists don't believe our sun has ever generated such a superflare. If one had, it likely would have triggered enough chemical change in the atmosphere to set off a mass-extinction of life on Earth. The only mass extinctions in geologic record have been tied to asteroid strikes, volcanic activity and related climatic change.

Ironically, a superflaring star may be a good place to look for habitable planets, Schaefer adds.


Tags: astronomy-space, stars