The search for alien life has become more difficult. Red dwarfs, the small and dim stars that many astronomers think may host life-supporting planets, come with an important feature: They often emit deadly flares of ultraviolet radiation, much stronger than astronomers previously thought.
Astronomers analyzed solar flares in 300,000 Milky Way stars using data collected by the GALEX space telescope. In a study published in Monthly notices of the Royal Astronomical Society, these researchers reported that the ultraviolet emission detected by the telescope between 2003 and 2013 was, on average, three times stronger than previously thought. In some cases, flares reach 12 times that level.
“Few stars have been thought to emit enough UV radiation through flares to affect the habitability of a planet. Our findings show that many stars may have this ability,” said Vera Berger, a graduate student researcher at the University of Cambridge, who led the study, in a statement.
Why red dwarfs shoot such powerful flares is not entirely clear. Jason Hinkle, Berger’s colleague, noted that red dwarfs are smaller and cooler than Earth’s Sun and emit less UV radiation than their flares. The team hypothesized that the unexpected intensity of these bubbles may be due to the concentration of UV radiation at short wavelengths, possibly caused by the presence of elements such as carbon and nitrogen in stars.
Whatever the cause, the flames would be a major obstacle to any possible life on nearby planets. UV radiation has a erosive effect on the atmosphere, which can disrupt the natural processes necessary for life to form and thrive on long scales.
This finding is similar to a 2020 paper that looked at Barnard’s Star, a 10-billion-year-old red star located about six light-years from Earth. The researchers determined that the star has a tendency to emit powerful UV flares that could have damaging effects on any planets in its habitable zone—the area around the star that is neither too hot, nor too cold to support life.
Red dwarfs make up about 75% of the known stars in the Milky Way. Because of how common they are, some astronomers have hypothesized that, if alien life is out there, most of it would be on the red zone planets. A paper published in 2013 stated that there are as many as 4.5 billion possible planets orbiting small stars in our galaxy alone. Openness aside, that theory has taken a few hits; a study in the same year concluded that many of the red exoplanets close to where life could flourish were attacked by the sun’s deadly winds. Another finding from 2016 is that many planets in the habitable zone of stars may actually be too hot for anything to survive.
Despite these constraints, scientists released a list in 2020 of 24 exoplanets that may be better suited to support life than Earth. That being said, if you’re lonely and hoping to find a creepy alien friend, don’t try to wish on a star. Red dwarfs are faint compared to our Sun, and none can be seen with the naked eye.
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