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Red dwarf star systems: Promising for life, but watch the apocalyptic flares

Red dwarf stars have several virtues that make them potential homes for Earth-like planets, but a new study suggests they also produce the largest solar flares ever seen.

By Staff writer / January 11, 2011

An artist's impression of the planetary system around the red dwarf Gliese 581.



Note from the Hubble Space Telescope: Looking for a home outside the solar system and considering that tempting-looking planet around an "old" red dwarf star? Check for flares from that star before you buy.

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Astronomers surveying 210,000 red dwarf stars toward the Milky Way's center have found that a relative handful of the oldest among them are sending flares of hot gas hurtling into the so-called habitable zones of those stars – an activity that has typically been associated with the youngest red dwarf stars.

That does not bode well for any otherwise-attractive planet that might be orbiting in that zone, suggests Adam Kowalski, a graduate student in astrophysics at the University of Washington in Seattle.


These stars were generating flares "much larger than the largest solar flares we've ever seen," says Mr. Kowalski.

He was part of a team conducting the survey, an effort driven in large part by the potentially rich hunting grounds red dwarfs present as locations for planets that might be hospitable for life. He presented the results during a briefing at the American Astronomical Society's winter meeting in Seattle, which runs through Jan. 13.

The trials of Gliese 581G

The interest is more than academic. Last September, a team of astronomers led by Steven Vogt of the University of California at Santa Cruz announced the discovery of two additional planets – including a possible Earth-mass planet, Gliese 581G – orbiting a red dwarf known as Gliese 581.

The team calculated that their candidate for an Earth-mass-planet was orbiting Gliese 581 in the star's narrow habitable zone – a region of space around the star where liquid water could remain stable on a planet's surface. Gliese 581 appears some 20 light-years from Earth in the constellation Libra.

It was a difficult detection, however, requiring data combined from major observatories in Hawaii and Chile. Two weeks later, Francesco Pepe, with the Geneva Observatory, reported that his attempt to provide independent confirmation of the discovery yielded no evidence for either new planet.

For now, Gliese 581G has been relegated to the scientific limbo known as "unconfirmed" discovery.

Rich planet-hunting grounds?

Similarly, red dwarfs – stars with less than half the mass of the sun – have had mixed success working their way onto some astronomers' lists of stars that might host habitable planets.


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