A group of astronomers recorded a strong burst of activity on Proxima Centauri, the closest star to the Sun, in March last year. Such outbursts call into question the possibility of the existence of life on the planet closest to us outside the solar system.
A reanalysis of last year's ALMA radio telescope data by a team led by astrophysicists at the Carnegie Institution found a bright flare last March on Proxima Centauri, a red dwarf and closest star to Earth (after the Sun). At the peak of luminosity, the intensity of radiation from our closest stellar neighbor was 10 times higher than the brightest solar flares ever observed in the same range. In just ten seconds, the star's brightness increased a thousand times. The big flash was preceded by another, weaker; together they lasted less than two minutes.
Stellar flares occur when fluctuations in the energy of a star's magnetic field accelerate electrons to speeds close to the speed of light. Electrons accelerated by the magnetic field interact with other charged particles of the plasma, which makes up most of the star's matter; this interaction leads to ejections of matter from the surface of the star, accompanied by intense radiation in all ranges of the electromagnetic spectrum.
"It is very likely that Proxima b, an exoplanet that orbits Proxima Centauri, received a huge dose of radiation during the outbreak," McGregor explains, adding that scientists previously knew that X-rays from its star periodically reach the planet, although less intensity. In the several billion years that have passed since the formation of Proxima b, outbreaks like March 2017 could completely deprive the planet of the atmosphere, liquid water and destroy any life if it had originated on the planet, the authors of the new work believe. However, scientists have previously questioned the possibility of life near red dwarfs, in particular due to the fact that stars of this type do not provide enough ultraviolet radiation for the birth of life.
Since its discovery in August 2016, Proxima b has been of great interest to astronomers and planetary scientists, primarily because it is located in the so-called habitable zone of its star. They are separated by only 7.3 million kilometers (for comparison, from the Earth to the Sun is 149.5 million km), however, the red dwarf Proxima Centauri is much colder than our star, therefore, even at such a relatively short distance on the exoplanet, according to calculations, liquid water can exist - an indispensable condition for the origin of life in the form we know.
In November of this year, scientists, based on the same data from the ALMA telescope, concluded that a disk of dust and gas exists around Proxima Centauri, similar to the Kuiper belt in the solar system, minus its large objects. Then the average brightness of the star for several months of observation (taking into account the outburst) was explained by the scattering of radiation on gas molecules and dust particles of the ring; at the same time, scientists suggested that in addition to the exoplanet Proxima b, one or more dense rocky bodies revolve around the star. But McGregor and her colleagues note that if we consider not the average luminosity of a star, but its dynamics, then you can notice a bright flash and abandon the assumption of a gas and dust ring and other planets or asteroids around Proxima Centauri.
An article by McGregor and her colleagues is being prepared for publication in the Astrophysical Journal Letters, a preprint published in the arXiv.org repository.
Ksenia Malysheva
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