Around three-quarters of the stars in our milky way are Red dwarfs - smaller, cooler relatives of our sun. Most of the so-called M-class stars have only about a tenth of a solar mass, and because of the slower sequence hydrogen fusion in its core, you have only up to five percent of their luminosity. But these dwarves, there are the planetary and the the even plenty. Astronomers estimate that in the milky way tens of billions of potentially life-friendly planets in Orbit around Red dwarfs exist. Around 40 percent of which could revolve in the habitable Zone – the distance from the star, allowing a mild climate, with liquid water. Alone in our immediate cosmic neighborhood already dozens of such exoplanets have been discovered, including the seven "Erdzwillinge" Trappist to the 40 light-years away in the star-1, two planets around our nearest neighbor Proxima Centauri and the two earth-like planets in the habitable Zone of the twelve light-years away, Teegardens star.

A red dwarf is only eleven light-years away

However, there are planets around Red dwarfs a catch: Because these stars are so dim, their habitable Zone is quite close to the star. This makes it easy for the astronomers, although easier to discover the planet – for example, on your effect of gravity on the star or by the shadowing of the star's light, if you pull in front of him over. At the same time, but this puts such a planet an increased risk. Because Red dwarfs are very active and regularly experience outbreaks and strong Radiation. Our neighbour star, Proxima Centauri, for example, produces per day, a good 60 weak Flares, and up to eight times per year, particularly violent outbursts. His planets are, therefore, always strong spurts of high energy UV and x-ray radiation. Therefore, has been controversial whether it can develop on planets in the habitable Zone of such stars at all life.

shows how the now current example, Gliese 887 (GJ 887), there are also Red dwarfs, which offer their guard a much calmer and friendlier environment. This Red dwarf is only about eleven light-years away from us and is, therefore, of the twelve tnächste star in our neighborhood. With optical telescopes seen GJ is not lit 887 as the brightest red dwarf in the sky, although he is even half as big as our sun. To search for possible planets around this star, astronomers have taken by Sandra Jeffers of the University of Göttingen him with the HARPS Spectrograph at the Very Large Telescope (VLT) of the European southern Observatory in Chile targeted. This Instrument allows to detect the slight shifts in the light spectrum caused by the gravity effect of one or more planets on the star movement. In addition, the researchers evaluated over 200 additional observation data from the past 20 years.

Two super-earths, maybe even three

they were in luck: "We have detected signals with a period of 9.3 days, and 21.8 days, and 50.7 days", reports Jeffers and her Team. Further analyses confirmed that the first two of these signals are most likely from the planet. In FY 887b and GJ 887c are super-earths with 4.2 and 7.6 masses, you are only a little larger than the earth. At the third Signal, the astronomers are not sure. The additional statistical tests were inconclusive, so that you can't yet exclude the possibility that the 50-day Signal but only a disruptive effect. The innermost Planet, GJ 887b, moves in an orbit, which is only 0.07 astronomical units (AU) from its star removed. So this super-earth with a temperature of around 200 degrees is probably too hot for life. The second Planet, GJ 887c, could do rather hope. After all, with an Orbit of 0.12 astronomical units, he moves just barely within the habitable Zone, which starts at 0.19 astronomical units. The astronomers estimate that the temperatures on GJ 887c be around 75 degrees.

should give it to the third planet around Gliese 887, then he would be even in the middle of the habitable Zone – would he be a good candidate for the search for life. Also positive: In contrast to most of the other Red dwarfs, GJ 887 seems to be a particularly quiet specimen of his star class, as the researchers using data from the TESS space telescope, NASA said. Accordingly, the radiation intensity varies in this star, only minimal, or possibly even only a smaller group of sun spots. The planets in this System would be exposed, therefore, only bit of hard radiation and could have due to the weak-star winds a thick, protective atmosphere. If this is the case, you could check the astronomers soon with the James Webb space telescope of NASA, which is expected to start at the beginning of 2021. "Should confirm further observations, then the existence of the third planet in the habitable Zone, then GJ 887 could be one of the most intensively studied systems in the solar neighborhood," writes Melvyn Davies from the Swedish Lund University, in a supplementary comment.

source: Sandra Jeffers (University of Göttingen), et al., Science, doi: 10.1126/science.aaz0795

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Date Of Update: 25 June 2020, 18:26