Kepler satellite telescope reveals hundreds of superflares on distant stars

May 17, 2012 by Bob Yirka report
A solar flare. Image: NASA

(Phys.org) -- Here on Earth we are occasionally concerned about solar flares due to the impact they can have on our electrical systems. But our solar flares are puny when compared to so-called superflares that occur with other stars. A new research study by a team from Japan’s Kyoto University has found after studying one patch of sky over a 120 day period in 1990 using data from the Kepler telescope, that superflares are rather common, and as they describe in their paper published in the journal Nature, some are a billion times as powerful as those that occur with our own sun.

Scientists have known about superflares for some time, though little is actually known about them. Nonetheless, over the past several years a near consensus had been reached regarding the reasons for their occurrence. Most in the field agreed that they were caused by interactions with what are known as “hot Jupiters,” huge planets in close proximity to the star. This new study undermines that theory; out of 365 superflares spotted occurring with 148 , not one of them had a hot Jupiter nearby. Because of this, astrophysicists are once again in the dark and must now go back and rethink the possibilities. Some have already suggested that instead of a hot Jupiter, perhaps there is a hot situation occurring, i.e. a more distant cooler planet interacting with the star. Unfortunately, such an interaction would be far more difficult to observe because such planets wouldn’t change the amount of light observed by Kepler as would hot Jupiters when they pass between our planet and their star.

The team also found that superflares occur more often with faster spinning stars; of the 365 superflares observed, only 101 occurred with slow rotating stars. They also found that stars that gave rise to superflares almost always had large sunspots as well. For these reasons, and because there is no evidence of such a large flare over the past 2000 years, the team doesn’t believe our own sun is capable of producing such large flares, which is good, because just one blast would destroy our ozone layer, making our planet uninhabitable in short order.

Scientists believe that flares from our sun come about when magnetic field lines that are connected to magnetically active parts on the sun, which we observe as spots, snap like a cut wire, sending electrically charged particles into space. Unfortunately, the same model doesn’t appear to hold for superflares because of the differences in scale. Thus, more research will need to be done to see if other models or theories can be built to help better explain this mysterious phenomenon.

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More information: Superflares on solar-type stars, Nature (2012) doi:10.1038/nature11063

Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 1029 to 1032 ergs of energy on a timescale of hours. Similar flares have been observed on many stars, with larger ‘superflares’ seen on a variety of stars, some of which are rapidly rotating4, 5 and some of which are of ordinary solar type. The small number of superflares observed on solar-type stars has hitherto precluded a detailed study of them. Here we report observations of 365 superflares, including some from slowly rotating solar-type stars, from about 83,000 stars observed over 120 days. Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun. The maximum energy of the flare is not correlated with the stellar rotation period, but the data suggest that superflares occur more frequently on rapidly rotating stars. It has been proposed that hot Jupiters may be important in the generation of superflares on solar-type stars, but none have been discovered around the stars that we have studied, indicating that hot Jupiters associated with superflares are rare.

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baudrunner
1.5 / 5 (4) May 17, 2012
As I see it, solar flares are ignition (as in fission/fusion) reactions of concentrates of the matter that is constantly being generated from the energy inside a star. They "seep" out through the fissures and crevices, of which there are always a few on the surface, which in the case of the sun is comprised of iron. It is solid - most of the time. Sunspots are the slag, the residue from those reactions that float in the plasma atmosphere, and that will eventually vaporise and/or be consumed. A star is a constantly changing and very dynamic cosmic body. Intense gravity tends to keep it all together, but that's not etched in stone.
MRBlizzard
1 / 5 (1) May 17, 2012
Sunspots have magnetic fields. Instead of releasing their magnetic field energy, many can get locked together like a log jam. The magnetic fields entagle without canceling. Eventually, all the potential energy in the complex of magnetic fields breaks out. Vast amounts of energy are available for the Mass Ejection; thus, super/ultra flares.

What I wanted to suggest is that this could be the re-heating event, that got the Earth out of the ice ball Earth.

I admit that I still think it was probably a lava release like the Siberian traps that released vast amounts of methane from methane clathrate. In the absence of such a lava flow, a large coastal uplift, or decrease in sea level (with water locked up on land), would decrease the stability/trapping pressure on the clathrate and cause it to release methane.

Yes, this last belongs elsewhere, back to super flares.
Terriva
1 / 5 (2) May 18, 2012
Sunspots have magnetic fields. Instead of releasing their magnetic field energy, many can get locked together like a log jam. The magnetic fields entangle without canceling. Eventually, all the potential energy in the complex of magnetic fields breaks out.
This is still way local explanation. I do perceive the sunspots like the bubbles raising inside of circulating solar plasma toward surface in similar way, like the bubbles inside of boiling fluid. When the solar system passes trough dense cloud of dark matter, and/or under certain constellation of heavy planets the center of mass of solar system may appear beneath the surface of Sun. Such an event breaks the solar cycle and it stops the normal circulation of Solar plasma with Coriollis force. As the result, a substantial volume of Sun can overheat like the pot of water inside the microwave oven. The sudden burst of massive sunspots and solar flares will release the latent heat accumulated beneath the surface of Sun after then.
Terriva
1 / 5 (2) May 18, 2012
The sparse and massive stars (red giants) are known for their instability, which is caused with imbalance of radiative pressure and gravity (i.e. shielding force, dual to pressure of radiation in AWT). Such imbalance may appear even at the case of much smaller stars, when the circulation of their plasma is violated from outside. There is no strict boundary between calm and pulsating stars. As the Sun will evaporate into radiation, we should consider, that its occasional bursts will become more frequent and intensive gradually. The unexpected wave of dark matter or sparse interstellar gas from outside of solar system would make the material of Sun relatively lighter and it may trigger the accidental flares too. For example, if some massive planet or brown dwarf (a Nibiru or PlanetX) would visit our solar system, it could trigger the massive flares due the gravitational disbalance of solar system - not to say about pile of asteroids, which would be deflected from their stable orbits...