Recent analyzes suggest that the ingredients needed for life may be lacking in red dwarf-centered systems, which account for 75% of all stars in the galaxy.
Three quarters of the stars in the observable universe may not allow life to develop, reveal new analyzes done on data from the Hubble Space Telescope and ESO’s Very Large Telescope. It is generally assumed today that 75% of the planets of the Milky Way revolve around red dwarfs. If that is truly the case, our hope about the possibility of “life elsewhere” in the Universe has somewhat been altered. But what makes these dominant stars so inhospitable?
Our Sun – which is not a red dwarf – has during the course of its evolution the presence of numerous comets and asteroids in orbit, often filled with water and organic compounds. Over time, some of these objects came to die on our planet, depositing in passing the seeds allowing life to appear and develop. The question here was whether red dwarfs could or could not allow this same luxury. And the latest analysis shows that the answer tends more to the negative.
Our Sun is a relatively stable star. This is why comets and asteroids have had the leisure to evolve more or less serenely. But the red dwarfs are different: smaller, of course, but much more unstable. AU Micro for example – a young star only 12 million years old, 32 light years away – seems very active, too much for the ingredients necessary for life to be kept around.
Significant stellar eruptions – still largely misunderstood – “act like a plow by pushing small particles – possibly containing water and other volatile substances – out of the system,” says Carol Grady of Eureka Scientific in Oakland, and lead author of the study. According to the analyzes, a protoplanetary disk formed around these stars could even disappear in only 1.5 million years. But life needs time to form (billions of years). And around the red dwarfs, time is lacking.
“These observations suggest that aquatic planets may be rare around red dwarfs because all the small bodies carrying water and organic matter are ejected by the extraction of the disc”, indeed confirms the researcher.
This new study, pessimistic as it is, adds to recent simulations published a few months ago. The latter then suggested that – even if a planet loaded with water had the chance to form around a red dwarf – the star would be so unstable that the atmosphere of the planet could be blown in a billion years only. Once again, life would be short of time.
Thus, the vast majority of the existing planets could finally be completely “dehydrated”, deprived of life forever. On paper the idea is not very pleasant. Those who see the glass as half full rather than half empty will argue that there is still 25% of stars around which it is possible for life to see the day.
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