There’s a red dwarf about 35 light-years from here that’s spewing powerful, life crushing solar flares into space. These types of stellar objects are fairly common, leading to speculation that our galaxy is less habitable than we thought.
Of the estimated 100 billion stars in the Milky Way galaxy, about three-quarters are red dwarfs. That’s obviously a lot, so suffice it to say, these cool, compact stars are important objects of inquiry among both astronomers and astrobiologists. If we’re to get a handle on our galaxy’s potential to spark and sustain life, we’ll need to understand where red dwarfs fit in the equation.
Discouragingly, a new study published in The Astrophysical Journal suggests that planets in orbit around red dwarfs may be subject to tremendously powerful and frequent solar flares, making it difficult—if not impossible—for life to emerge in such systems.
At first glance, M9 dwarf TVLM 513-46546 doesn’t seem like something that could cause so much trouble. In fact, this thing barely registers as a star; like any red dwarf, it’s on the cusp of being able to fuse hydrogen. A closer glance, however, has revealed some startling details.
The first thing that scientists noticed was its extraordinary rate of spin. Unlike our Sun, which requires an entire month to make a full rotation, this red dwarf spins once every two hours.
But that’s not all. Measurements taken during an earlier study shows that its magnetic field is several hundred times stronger than our Sun’s. This seemed weird because the physics required to generate such a powerful magnetic field shouldn’t occur in such a small star.
The new study, conducted by researchers at the Harvard-Smithsonian Center for Astrophysics, has revealed yet another anomaly. Using the new Atacama Large Millimeter/submillimeter Array, a team led by Peter Williams discovered an emission frequency of 95 GHz. A high frequency such as this has never been observed before in a red dwarf. Our own Sun can produce solar flare emissions of this magnitude, but it does so only very rarely.
The researchers also discovered that the emissions from this ultracool dwarf is 10,000 times brighter than what our Sun produces—despite the fact that it has less than one-tenth the mass of our Sun. These bursts, which were measured over a 4-hour period, suggests this thing is basically active all the time.
“If we lived around a star like this one, we wouldn’t have any satellite communications,” noted Williams in a release. “In fact, it might be extremely difficult for life to evolve at all in such a stormy environment.”
Indeed, these measurements have serious implications for astrobiologists as they search for habitable exoplanets. Because red dwarfs are so cool, planets would have to be parked in close orbit to sustain surface water, and thus be deemed potentially habitable. But as noted by the Harvard-Smithsonian researchers, that proximity “would put the planet right in the bull’s-eye for radiation that could strip its atmosphere or destroy any complex molecules on its surface.” It would be like living in Tornado Alley.
“A planet in the habitable zone of a star like this would be buffeted by storms much stronger than those generated by the Sun,” added Williams.
The astronomers aren’t sure if M9 dwarf TVLM 513-46546 is an anomaly, or if it’s an example of an entire class of stormy stars. Looking ahead, they plan on studying similar stars to find out.
Read the entire study at The Astrophysical Journal: “The First Millimeter Detection of a Non-Accreting Ultracool Dwarf”.
Email the author at firstname.lastname@example.org and follow him at @dvorsky. Images by NRAO/AUI/NSF; Dana Berry / SkyWorks