Young red dwarfs are incredibly active, emitting bursts of such intensity and frequency that potential life for these stars should be especially difficult.
Three quarters of the stars in the Milky Way are small and relatively cool red M-class dwarfs. They shine dimly, but they are able to maintain stability, theoretically, up to tens of trillions of years. All this makes their exoplanets promising candidates for the development of life. However, the authors of a new article published in The Astrophysical Journal have shown that red dwarfs can be extremely life-threatening luminaries.
Parke Loyd and his colleagues are studying red dwarfs and their surroundings as part of a specialized program of the Hubble space telescope - HAZMAT (HАbitable Zones and M dwarf Activity across Time). Indeed, moderate and stable red dwarfs provide their planets with comfortable regions in which temperatures are neither too high nor too low, allowing liquid water, one of the key living conditions, to persist. However, the needs of biochemical evolution are not limited to moisture.
Development safety is perhaps equally important, and life on such planets can have problems with it. HAZMAT observations in the far-UV range allowed us to examine the surfaces of 12 young red dwarfs located at a distance of 120 to 165 light years. And in less than a day of monitoring, as many as 18 powerful flares were recorded on them, the energy of ten of which exceeded 1023 J is the amount that comes to the Earth from the calm Sun for a whole week. And the most powerful even got its own name - Hazflare - and was 1025 J.
“We've been observing the Sun for hundreds of years, and during that time we've seen one, maybe two, flares that are at least close to Hazflare,” says Park Loyd. “At the same time, we caught Hazflare in less than a day of Hubble observations of these young. This means that such outbreaks occur there daily, or even more often. " If young red dwarfs do show such vigorous activity, then for life in their vicinity this can be a big problem. These flares are capable of "blowing" the atmosphere, depleting and weakening it.
On the other hand, this is not yet a verdict. Yes, conditions on such planets should be harsher than on our comfortable Earth, but they are not beyond the possible, and life is quite capable of adapting to them. "It's a tough environment, of course," says Park Loyd, "but I wouldn't say it is sterile." In addition, red dwarfs older than several hundred million years in the middle and late stages of their existence already "calm down" and do not show such dangerous outbreaks.