Astronomers have found an unusual object in the constellation Pisces that occupies an intermediate position between giant planets and brown dwarfs, failed stars, according to an article published in the Astrophysical Journal Letters.
“The transfer of SIMP0136 from among brown dwarfs to the elite club of 'independent' giant planets that escaped their stars was a pleasant revelation for us. In the past, we have already found hints of the existence of weather on this object, even when we considered it a brown dwarf, and studying it will help us shed light on the composition and behavior of the atmosphere on other exoplanets,”explains Ethienne Artigau from the university Montreal (Canada).
Brown dwarfs, the first of which were found in 1995, astronomers call transitional objects between stars and planets. The mass of such failed stars - less than 7% of the mass of the Sun - is too small for a thermonuclear reaction to occur in their bowels. Therefore, brown dwarfs gradually fade away and cool.
In recent years, scientists have discovered a number of unusual features of brown dwarfs - the presence of weather on them, lead and mineral "clouds" and a number of other properties, which led many astronomers to believe that they are in fact very large planets, and not stars.
Artigo and his colleagues found that the boundary between planets and stars is even more blurred by studying the properties of what was previously thought to be one of the coldest and most unusual brown dwarfs - the object SIMP0136 in the constellation Pisces. It was discovered in 2006 in one of the clusters of young stars, born about 200 million years ago, at a distance of 20 light years from Earth.
The short distance to this star allowed the astronomer to very accurately measure the temperature of its surface, calculate its chemical composition and reveal other properties, including hints of the existence of difficult weather conditions in the atmosphere of SIMP0136. Everything, Artigo says, indicated that SIMP0136 is an unusually cool and interesting brown dwarf of low mass.
Observing this object last year, astronomers decided to re-measure its mass and speed across the sky. These observations, according to Artigo, were helped by the "brothers" of this dwarf in the cluster, which have a similar age and speed of movement, but brighter and more convenient for studying.
The results of these routine measurements were extremely unexpected. It turned out that SIMP0136 is located exactly on the border between giant planets like Jupiter and brown dwarfs. So, its mass is only 12-13 times greater than that of the largest planet in the solar system, and its radius is only 20% larger than that of Jupiter. Together with the relatively low surface temperature - about 800 degrees Celsius - all this does not allow us to consider SIMP0136 a "pure" brown dwarf.
Scientists believe that this half-planet-half-star was formed in the company of another star, but then it was thrown out of the system, becoming a kind of "outcast" planet. Such planets are especially interesting to astronomers, since their radiation is not "clogged" by the light of brighter stars, which makes it possible to accurately determine the composition of their atmosphere, monitor the movement of large air currents in it and reveal other physical and chemical secrets.