The planet most similar to the Earth is most likely unsuitable for life
Astronomers from the University of Warwick have given a disappointing forecast for the planet Kepler-438b, which was considered the most similar to the Earth of the exoplanets discovered to date. Periodic powerful coronal mass ejections with Kepler-438, the stars around which the planet revolves, could completely destroy its atmosphere.
It turned out that the Kepler-438 star, a red dwarf, emits powerful flashes every few hundred days, in intensity exceeding the strongest solar flares by an order of magnitude. But the atmosphere is not directly affected by them, but by coronal mass emissions. These are massive emissions of gas and electromagnetic radiation from the stellar corona, which introduce strong perturbations into the magnetic field of the star. After a rapidly occurring solar flare, plasma rushes into space from the star (consisting mainly of electrons and protons).
The planet Kepler-438b most similar to the Earth is called according to the Earth Similarity Index (ESI). This index, which shows the probability of living conditions on the planet, is based on several factors of its physical similarity to the Earth: size, mass, density, distance from the star and temperature on the planet. For Earth, this index is a strict unit; for Kepler-438b, this figure is 0.88. The next planet on the list, Kepler-296 e, has an ESI of 0.85.
“If Kepler-438b has the same magnetic field as the Earth, it can be partially protected from the effects of [coronal mass ejection]. But if it is not strong enough for such powerful flashes, it could completely lose its atmosphere, become dangerously irradiated and be less suitable for life than it might seem at first glance, ”explains Dr. David Armstrong, the lead author of the work , University Astrophysicist [David Armstrong].
Strong flares of the star, among other things, lead to the irradiation of the planet Kepler-438b with ultraviolet and X-ray radiation, which also badly affects its ability to maintain our usual forms of life.
In addition to the Earth similarity index, there are other methods for ranking exoplanets by life support options - for example,transit planet habitability index .