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Rare 'superflares' could one day threaten Earth



 Rare "superflares" could one day threaten Earth
An artist's depiction of a superflare on an alien star. Credit: NASA, ESA and D. Player
            

Astronomers probing the edges of the Milky Way in recent years observed some of the most brilliant pyrotechnic displays in the galaxy: superflares.
                                               


These events occur when stars, for reasons that scientists do not understand, eject huge bursts of energy that can be seen from hundreds of light years away. Until recently, researchers found that such explosions occurred mostly on stars that, unlike Earth's, were young and active.

Now, new research shows with more confidence than ever before that superflares can occur on older, quieter stars like our own ̵

1; albeit more rarely, or about once every few thousand years.

The results should be a wake-up call for life on our planet, said Yuta Notsu, the lead author of the study and a visiting researcher at CU Boulder.

If superflare erupted from the sun, it said, Earth would probably be in the path of a wave of high-energy radiation. Such as blast could disrupt electronics across the globe, causing widespread black outs and shorting out communication satellites in orbit.

Notsu will present his research at a press briefing today at the 234th meeting of the American Astronomical Society in St. Louis.

"Our study shows that superflares are rare events," said Notsu, a researcher at CU Boulder's Laboratory for Atmospheric and Space Physics. "But there is some possibility that we could experience such an event in the next 100 years or so."

Scientists first discovered this phenomenon from an uniquely source: the Kepler Space Telescope. The NASA spacecraft, launched in 2009, features out planets circling stars far from Earth. But it also found something odd about those stars themselves. In rare events, the light from distant stars came to, and momentarily, brighter.

Researchers dubbed those humongous bursts of energy "superflares."

Close to home that normal-sized flares are common on the sun. But what the Kepler data was showing much bigger, on the order of hundreds of thousands of times more than the largest ever recorded with modern instruments on Earth.

And that raised an obvious question: Could a superflare also occur on our own sun?

"When our sun was young, it was very active because it was very fast and probably generated more powerful flares," said Notsu, also of the National Solar Observatory in Boulder. "But we didn't know if such large flares occur on the modern sun with very low frequency."

To find out, Notsu and an international team of researchers turned to data from the European Space Agency's Gaia spacecraft and from the Apache Point Observatory in New Mexico. About a series of studies, the group used those instruments to narrow down a list of superflies that had come from 43 stars that resembled our sun. The researchers then conducted those rare events to a rigorous statistical analysis. Based on the team's calculations, younger stars tend to produce the most superflares. But older stars like our sun, now a respectable 4.6 billion years old, are off the hook.

"Young stars have superflies once every week or so," Notsu said. "For the sun, it's once every few thousand years on average."

The group published its latest results in May in The Astrophysical Journal .

The solar light show is due to hit Earth. But he said that it's a matter of when, not if. Still, that could give humans time to prepare, protecting electronics on the ground and in orbit from radiation in space.

"If a superflare occurred 1,000 years ago, it was probably no big problem. People may have seen a large aurora," Notsu said. "Now, it's a much bigger problem because of our electronics."
                                                                                                                        


Kepler satellite telescope reveals hundreds of superflares on distant stars


More information:
Yuta Notsu et al. Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars? —Results Using APO 3.5m Telescope Spectroscopic Observations and Gaia-DR2 Data, The Astrophysical Journal (2019). DOI: 10.3847 / 1538-4357 / ab14e6

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University of Colorado at Boulder

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                                                 Rare 'superflares' could one day threaten Earth (2019, June 11)
                                                 retrieved June 11, 2019
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