In the constellation Bear researchers have for the first time tracked down a giant gas planet, which revolves around a small dwarf star. The discovery questions common theories of physics about the formation of planets, experts in the journal "Science" report.
In itself, the gas planet is nothing special, but the star around which it circles, actually has too little mass to accommodate such an object in the solar system: "GJ 3512", a so-called red dwarf star, owns just 12 percent of our mass Sun. At the same time, the gas planet is at least half as massive as Jupiter, the largest planet in our solar system.
In other words, while the mass ratio between our Sun and the orbiting Jupiter is 1050 to one, it is just 270 to one in the Dwarf star "GJ 3512" and the newly discovered gas planet.
"To find stars like 'GJ 3512' are typically several planets the size of our planet and perhaps even more massive super-terrestrials," explains Christoph Mordasini of the University of Bern. As an example, he calls the dwarf star Trappist-1. It has similar characteristics as "GJ 3512", but instead of a gas giant it is surrounded by seven planets with at most the mass of the earth.
This corresponds to the common theory for the development of planets.
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Accordingly, planets are made of the same material as the stars around which they circle later. The starting point is a rotating disk of gas and dust, in the center of which the material is increasingly compressed. If the temperature and pressure are high enough, nuclear fusion occurs there - a star is formed. Outside, solid particles are forming, collecting more and more material and forming a gas envelope by gravity - the planets.
Too little material for a giant planet
The problem: According to the theory, the gas and dust disks, from which low-mass stars such as "GJ 3512" develop, contain too little material to be able to develop large gas planets.
The unusual giant planet was tracked down by a Spanish-German research consortium in which the Max Planck Institute for Astronomy in Heidelberg also participates. Using a special instrument at the Calar Alto Observatory in southern Spain, the researchers observed the dwarf star "GJ 3512". They found that he regularly moves away from us and back to us.
Guillem Anglada-Escude / IEEC
Comparison of the "GJ 3512" system with other dwarf star systems
The phenomenon could only be explained with a very massive planet orbiting the star. The gas giant named "GJ 3512b" is located about 30 light-years from our sun. One year has 204 days there. However, the researchers were unable to conclusively clarify how exactly it was created. But they suspect that it has evolved directly from the gas and dust, rather than grow slowly from a solid particle.
The background is the mechanism of the so-called gravitational collapse. "Part of the gas disk in which the planets are formed collapses under their own mass," Mordasini explains. This is possible, among other things, because it is very cold in the outer area of the disc with temperatures of minus 160 degrees. The thermal pressure can then compensate for the gravity of the swirling particles worse, they collapse. In this case, according to the scenario, planets can arise.
However, there are inconsistencies. "Why did not the planet continue to grow and position itself closer to its star?" Asks Mordasini. Both are to be expected if one assumes that the gas and dust disk contained enough material to become unstable by its own gravity.
The researchers hope to use GJ 3512 to better understand how planets are formed around low-mass stars.