Tiny Star Shoots Out Flares 10,000 Times Brighter Than the Sun's (Dec 2015 Space.com)

A small, cool star is emitting flares 10,000 times brighter than those ejected by the sun, a find that could be bad news for those hoping to find the galaxy filled with life.
The star's massive bursts of radiation, revealed in new research, could inhibit the evolution of life on planets orbiting the star, or at least severely disrupt it. If other stars of this type also have such intense flares, it could mean life in the universe is less likely to develop.
"If we lived around a star like this one, we wouldn't have any satellite communications," Peter Williams, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. Williams leads a team of researchers in studying the star using the Atacama Large Millimeter/Submillimeter Array (ALMA), a massive radio telescope in Chile.
"In fact, it might be extremely difficult for life to evolve at all in such a stormy environment," Williams said in the statement.
"A very different beast"
Dim red dwarf stars dominate in the Milky Way, making up about three-fourths of the stellar population of the galaxy. The well-known star Williams targeted is a cool red dwarf, less than 1 percent as massive as the sun. It lies about 35 light-years from Earth, in the constellation Boites.
Previous studies of the star from the Karl G. Jansky Very Large Array in New Mexico revealed that the tiny star has a magnetic field several times stronger than the sun, although the physical processes that build the sun's magnetic field shouldn't work for such a small star.
"This star is a very different beast from our sun, magnetically speaking," CfA co-author Edo Berger said.
Williams and his team turned ALMA's powerful focus toward the tiny star, making the first detections of flarelike emissions from a red dwarf star at such high frequencies.  The bursts of light created by the flares are 10,000 times brighter than those produced by the sun. Their presence in the short window of observations suggests that such flares are constantly being produced.
In their research, which has been accepted for publication in The Astrophysical Journal, the scientists named ALMA's extreme sensitivity as the key to detecting the flares. The measurement not only reveals more about the tiny star, but also opens the door to investigating other ultracool red dwarfs.
Bad news for life
If such emission is consistent across red dwarfs, it could mean bad news for the ability of life to evolve in the galaxy. Red dwarfs dominate the Milky Way, making up about three-fourths of all stars. Since NASA's Kepler telescope found planets around these worlds, the debate over whether or not they could host life has gone back and forth.
In order to hold liquid water on its surface, a condition necessary for life to evolve, a planet orbiting a dim red dwarf must lie significantly closer to its star than Earth lies to the sun. This region is known as the habitable zone. But its close proximity puts the planet at risk from stellar flares and coronal mass ejections, bursts of charged particles that stream out from a star. Stellar winds also carry charged particles away, potentially toward the planet.
If radiation reaches the surface of a planet, it can be damaging for any life growing there. Earth has a thick atmosphere that blocks most of the sun's rays, but the radiation that comes from orbiting very close to a red dwarf could tear away that type of protection. Plus, the extra-intense activity found around the ultracool red dwarf studied by Williams' team may make it even more challenging.
"It's like living in Tornado Alley in the U.S. Your location puts you at greater risk of severe storms," Williams said.
"A planet in the habitable zone of a star like this would be buffeted by storms much stronger than those generated by the sun."

Red Dwarf Stars May Be Best Chance for Habitable Alien Planets

Stars known as red dwarfs might have larger habitable zones friendly to ‘life as we know it’ than once thought, researchers say.


Red dwarfs, also known as M stars, are dim compared to stars like our sun and are just 10 to 20 percent as massive. They make up roughly three-quarters of the stars in the galaxy, and recently scientists found red dwarfs are far more common than before thought, making up at least 80 percent of the total number of stars.


The fact that red dwarfs are so very common has made astrobiologists wonder if they might be the best chance for discovering planets habitable to life as we know it. More and more planets are getting discovered around red dwarfs — for instance, a potentially habitable "super-Earth" at least 4.5 times the mass of Earth, GJ 667Cb, was recently found orbiting the red dwarf GJ 667C.


"More of these planets are being found, so research is moving from being theoretical and predictive to using actual data from extrasolar planets," said researcher Manoj Joshi, an atmospheric physicist at the University of East Anglia in England.


Since red dwarfs are so cold compared to our sun, planets would have to be very close in to be habitable to any life as we know it —  in many cases, less than the distance between Mercury and our sun. This closeness actually makes them appealing to hunters of alien worlds — planets near their stars eclipse them more often, making them easier to detect than planets that orbit farther away.


However, being too close to a star can have its disadvantages. For instance, the gravitational pull of the star would cause tides that could wreak havoc on such a world, perhaps leading to a so-called "tidal Venus" scenario where it loses all of its surface water. Also, young red dwarfs less than 3 billion years old may be very active, firing off flares several times per day, causing ultraviolet radiation to jump by 100 to 10,000 times normal levels and potentially sterilizing the surface of a nearby planet or even helping to strip off its atmosphere.


Now scientists find that planets may remain habitable farther away from a red dwarf than once thought. This in turn could mean there is a chance there are far more habitable worlds around red dwarfs than previously suspected.


The habitability of a star depends on how warm or cold it is, which in turn rests in large part on how much starlight it absorbs and reflects. Frozen water such as ice and snow reflects light, which means it helps cool planets, including Earth.


"If a rocky planet forms around an M-star and it has water on it, if it gets cold enough, that'll turn to ice or snow," Joshi said. "As for the odds of rocky planets forming around M-stars, Neptune- and sub-Neptune-sized objects have been found, so chances could be good."


The researchers modeled how reflective ice and snow would be on simulated planets orbiting two real-life red dwarfs. Ice and snow are less reflective against longer, redder wavelengths, while red dwarfs obviously have fairly red light to begin with.


The scientists found that any such planets encircling red dwarf stars would absorb more of their light than previously thought, leading to significantly warmer surfaces. This means the outer edge of the habitable zone around red dwarfs might be 10 to 30 percent farther away from its parent zone than once suggested.


"I was surprised that the effect was as large as it was," Joshi told Astrobiology Magazine. "The zone where liquid water is stable on a planet's surface is farther away from such stars than previously thought."


Joshi cautioned they only looked at the effects of water ice and snow, when other kinds might be important when considering how much energy a planet absorbs and reflects, such as frozen carbon dioxide, nitrous oxide and methane. Also, "we didn't look at the effects of atmospheric absorption of radiation by gases such as water vapor or carbon dioxide," he added. "That should be done in future."


Joshi and Robert Haberle detailed their findings in the Jan. 23 issue of the journal Astrobiology