But not all ultraviolet radiation is harmful: near-ultraviolet, waves of about 175-275 nanometers, are just what can encourage the diversification of life, while the real danger comes from waves of 135-175 nanometers, the so-called far-ultraviolet.
In solar flares, the ratio of the intensity of far and near ultraviolet rays is approximately 1:6. It is generally believed that a similar ratio should exist in the flashes of other stars. Based on this assumption, conclusions are drawn about the favorability of exoplanets for life.
But now scientists have discovered that this assumption is completely wrong. They collected data on 182 flashes in 158 stars. It was possible to observe all the flashes in detail both in the near and far ultraviolet range and to determine the intensity of the radiation and its change during the development of the flash.
It turns out that the ratio of far/near ultraviolet intensities in flashes is between 1:2 and 2:1, which is 3-12 times higher than previously thought.
The total energy emitted by the flash in the far ultraviolet is also three times higher than predicted by the previous model. In addition, the higher the total energy of the flash, the higher the proportion of far ultraviolet.
Finally, the fraction of far-ultraviolet is higher in redder stars – that is, those that are smaller than the Sun.
All these results indicate that it would be difficult for possible life to arise and survive on many known planets.
Most exoplanets orbit small red stars with flares similar in intensity to, or even stronger than, the Sun. It has long been debated whether such bright planets, which orbit much closer to the stars than the Earth is from the Sun, would sterilize or even support the spread of life.
The new results suggest that the first explanation is much more likely.
The results of the study are published in the magazine “MNRAS”.
2024-08-17 04:46:46