Scientists warn 'superflares' could pose threat to Earth

An Incredibly Powerful White Light Superflare Erupted from a Small Faint Star

An illustration of a super flare on an L-dwarf. Credit University of Warwick Mark Garlick

Astronomers have been looking at the edges of the Milky Way galaxy have seen some very intense superflares originating from stars.

They estimated that Sun-like stars that rotate slower, roughly once every 25 Earth days, eject superflares about once every 2,000 to 3,000 years with an energy no more than 5 x 10 erg.

Superflares used to be thought of as a younger-star phenomenon, researchers said in a statement about the new study, but the new work suggests it can happen on the sun at rare intervals, of perhaps once every few thousand years.

Now scientists at the University of Colorado Boulder are warning that our own sun is prone to the odd superflare eruption that could easily hit Earth - and in fact one may be long overdue. The team estimates that calm stars like the Sun have superflares about every 1,000 years.

Among the potential consequences, such an event could lead to blackouts all around the world, or cause satellites in orbit to malfunction-disabling communications technologies, global positioning systems and more.

"Our study shows that superflares are rare events", said Notsu, a researcher in CU Boulder's Laboratory for Atmospheric and Space Physics.

To investigate, Dr Notsu and his colleagues from Japan, the United States and the Netherlands studied superflares detected from 43 Sun-like stars using data from the European Space Agency's Gaia spacecraft and New Mexico's Apache Point Observatory. They noticed that, at times, the light from some distant stars, hundreds of light-years away, would rapidly get brighter for a relatively short period of time.

Be that as it may, Notsu says the more we learn about superflares, the more we realise that while they might be more common on younger stars, Sun-like stars are definitely not precluded from this powerful, and potentially very risky form of stellar phenomena. However, what the Kepler data was showing seemed to be much bigger, on the order of hundreds to thousands of times more powerful than the largest flare ever recorded with modern instruments on Earth.

These superflares are mainly observed in young, active stars. But older stars like the Sun could have superflares every few thousand years on average while younger stars have superflares every week or so. These events are far more powerful than the flares that are often produced by our sun.

And that raised an obvious question: Could a superflare also occur on our own sun? However, older stars like the Sun - which is 4.6 billion years old - also produce them occassionally.

'If a superflare occurred 1,000 years ago, it was probably no big problem, ' Dr Notsu said, explaining that people may have seen a large aurora as a result of the event.

"Now, its a much bigger problem because of our electronics".

Co-authors on the recent study include researchers from Kyoto University, the National Astronomical Observatory of Japan, University of Hyogo, University of Washington and Leiden University.

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