“It’s like living in Tornado Alley in the U.S.” That’s how Peter Williams of the Harvard-Smithsonian Center for Astrophysics (CfA) describes what it would be like living near M9 dwarf TVLM 513-465496.
It’s a red dwarf star about 35-light years away from Earth in the constellation Boîtes. Red dwarf stars are small, but this one skirts the line between being a star (fuses hydrogen) and a brown dwarf (which doesn’t).
While much smaller than our Sun, TVLM 513 packs a stormy surprise. Astronomers knew from previous data that this star’s magnetic field was much stronger than our Sun’s. And it puzzled them. The processes behind our Sun’s magnetic field shouldn’t be seen in a much smaller star.
Williams and his colleagues took another look at the star with the Atacama Large Millimeter/submillimeter Array (ALMA). They detected flare-like emissions at a frequency of 95 GHz. We all know our Sun generates solar flares, but nowhere near as often as this dwarf star. Not only is TVLM 513 pumping out solar flares more often, but they are also 10,000 times brighter than flares from our Sun.
Plus, ALMA only observed the star for 4 hours. TVLM 513 could be generating solar flares continuously.
What would it be like living near this star? Say goodbye to Google Maps and hello again to road atlases. “If we lived around a star like this one, we wouldn’t have any satellite communications. In fact, it might be extremely difficult for life to evolve at all in such a stormy environment,” says Williams.
Bad news for habitable planets
Red dwarfs are promising targets for astronomers looking for habitable planets. Why? Because there are so many of them. Red dwarfs are the most common type of star in our galaxy. But, this discovery is throwing more cold water on them.
Because of how “cool” they are, red dwarfs present several problems for potentially habitable worlds. The Goldilocks zone (area where liquid water could exist) is much closer with red dwarfs.
And Williams’ team shows that this proximity would put any habitable world right in the path of harmful radiation. At least, in TVLM 513’s case. The solar flares and radiation from the star would quickly strip a planet’s atmosphere and destroy any complex life (as we know it) on its surface.
Tidal locking would also be a problem. Because of the need for a closer orbit, any planet would likely become tidally locked. One hemisphere would always face the star. The other would freeze as it stays permanently in the shadows. A great example of this is our moon. We always see the same side of it.
Maybe TVLM 513’s solar flare output is an outlier? That’s what astronomers will look for next. TVLM 513 could just be a unique star. Or, it could be the first discovery of a new class of stormy stars.
Williams and his team also praised ALMA for making the discovery possible.
Finally, we note that these results could only be obtained thanks to ALMA’s superior sensitivity compared to any previous mm-band instrument. This first detection marks the opening of a new window for intensive investigations of the magnetic dynamo and particle acceleration processes that are jointly responsible for the cm/mm emission of ultracool dwarfs.
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