Scientists have found further evidence that red dwarfs, once thought to be a bastion for habitability, may not be the oases of life we were looking for.
Using data from NASA’s Galaxy Evolution Explorer (GALEX) spacecraft, researchers found that red dwarfs undergo both large and small flares that could erode the atmospheres of nearby planets. They could also damage any life on the surface, or prevent it arising at all.
The research was led by Chase Million of Million Concepts in State College, Pennsylvania, and presented this week at the 230th meeting of the American Astronomical Society in Austin, Texas.
The team looked at 10 years of observations by GALEX, which monitors stars in the ultraviolet wavelength. Red dwarfs themselves are dim in ultraviolet (but strong in infrared), which allowed the researchers to see even small ultraviolet flaring events.
Looking at several hundred red dwarf stars, they saw dozens of flares. These ranged “from itty bitty baby flares that last a few seconds, to monster flares that make a star hundreds of times brighter for a few minutes,” Million said in a statement. All the flares were similar in power to those from our own Sun, but as the planets are much closer, they are subjected to more of their potentially damaging energy.
While only a few dozen were found, the team said they expected to find hundreds of thousands of flares in the GALEX data. That’s not a good thing – the more we find, the less promising red dwarfs become.
Recently, these stars have shot to the fore in the search for life. Red dwarfs are the most common stars in our galaxy by far, making up three-quarters of our stellar population. They are also relatively dim and have planets in tight orbits, which makes these worlds easier to study than other stars as they transit (cross the face) of the star more frequently and noticeably.
In this past year, systems like TRAPPIST-1 and LHS 1140, with Earth-sized worlds in the habitable zones, have garnered a great deal of excitement. But the threat of flares has remained ever present. Now it seems we may have underestimated the threat.
That does not mean habitable worlds around these stars cannot exist. After all, the atmospheres of Earth and Venus both survive solar flares in our own Solar System. But it might put a dampener on just how habitable worlds like Proxima b could be.
We won’t know for sure until more powerful telescopes come online in the future though, such as NASA’s James Webb Space Telescope (JWST). These will be able to probe the atmospheres of distant planets, and look for signs of life.
“The argument of the flares and higher ultraviolet flux environment has been done several times before and it will be done again,” astronomer Guillem Anglada-Escudé from Queen Mary University of London, who was not involved in the research, told IFLScience.
“From my point of view, all these are arguments that need to be taken into account when we eventually detect their atmospheres (if any) and features in them.”
Time will tell if these worlds are dead and barren, or somehow defy the odds.