Red dwarfs always remind me of the classic British science comedy on the television of the 90s, which was named after them. However, the stars themselves are hardly similar to the show. These are small, not surprisingly red stars that can generate flares and coronal mass stirs that can keep up with many of the much larger stars. A team of astronomers recently used the Chandra X-ray observatory to investigate Wolf 359 and found that it triggers brutal X-rays that would be extremely harmful to life on nearby planets.
Red dwarfs are small, cool and very durable stars that only shine with a fraction of the brightness of our sun. They have a mass of less than half of the sun mass and their surface temperatures are between 2,500 and 4,000 degrees Celsius. Since they slowly burn their fuel, red dwarfs can survive trillions of years and thus surpass the lifespan of massive stars many times over. They are widespread throughout the cosmos and make up about 70–80 % of all stars in the galaxy. Nevertheless, they are difficult to recognize with the naked eye.
An artistic impression of Trappist-1 B, shortly before he passes the cool, red dwarf star Trappist-1. Such stars are known for their activity with large star stains and eruptions. Trappist-1 B can be exposed to intensive volcanism. Photo credits: Thomas Müller (HDA.mpia)
Wolf 359 is one of these red dwarf stars, which is about 7.8 light years away from the earth and is therefore one of the stars closest to our solar system. It is still too dark to be seen without a telescope, although it only has a thousandth of the brightness of the sun. It is part of the Lion constellation and has a mass of only about 12 % of the mass of our sun, with a surface temperature of around 4,000 degrees Celsius. Wolf 359 is a relatively young star, but due to its small mass, it will slowly burn his hydrogen fuels and could remain stable for several dozen billions of years.
Due to the intensive radiation emissions of Wolf 359, it is very likely that the planets in the orbit will not be able to maintain a stable life -resistant atmosphere. However, a team of astronomers examined it with the Chandra X-ray observatory of the NASA and the XMM Newton of the ESA. They found that only a planet that contains greenhouse gases such as the earth could enable lives. Since red dwarfs are the most widespread stars in the universe, astronomers have researched them in order to find information on exoplanets, but so far with little success. The team found evidence of two planets in orbit around Wolf 359, but not all scientists are convinced.
Artistic illustration of Chandra
Each star has a habitable zone and its location is determined by the temperature and the energy output of the star itself. The external boundaries of this zone around Wolf 359 are about 15 % of the distance between earth and the sun. The two exoplanets that have not yet been confirmed circle the star outside the habitable zone; One is too close, the other too far.
While they examined the system for 3.5 days, they observed 18 X -rays from Wolf 359. However, that was a little more than 3.5 days and the team assumes that more and more harmful outbreaks will occur from time to time. These intensive x -rays are the main reason that all planets in the orbit must be within the habitable zone and need a carbon dioxide -rich atmosphere to maintain habitable conditions. However, it is unlikely that a planet can maintain its atmosphere within the habitable zone due to the strength of the wind blowing on it.
Source: Exoplanets must be prepared for extreme space weather, Chandra Find
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