Many "hot Jupiters", the most "hellish" planets of the Universe, arise directly in the vicinity of the star, and not only migrate there afterwards, as scientists previously believed. This is the conclusion reached by planetary scientists who published an article in the arXiv.org electronic library.
“Our calculations show that at least some of the 'hot Jupiters' should have formed in the same place where they are now. Of course, this does not exclude the possibility of their migrations in principle, but it suggests that such events, which were previously considered the norm, actually happen extremely rarely,”writes Konstantin Batygin from the California Institute of Technology in Pasadena (USA).
Astronomers call "hot Jupiters" heated gas giants that are only 2.2-75 million kilometers away from their stars (in the Solar System, even Mercury approaches a star no closer than 46 million kilometers), so the atmospheres of such planets really reign hellish temperatures - about 1000 degrees Celsius.
The discovery of the first "hot Jupiters", as noted by Batygin and his colleague Elizabeth Baily, came as a big surprise to scientists who began to argue about how and where such planets arise.
“The solar system has long been our only example of what a planetary system looks like and how it can form. For example, we have long believed, relying on the masses of Mercury and other inner worlds, that large planets cannot form in the immediate vicinity of stars. “Hot Jupiters” did not fit into this picture,”the scientist continues.
Today, many planetary scientists believe that this anomaly can be explained using the same mechanism that describes the birth of the giant planets of the solar system. "Hot Jupiters", like their cold namesake, should have been born in the cold part of the protoplanetary disk and later migrated towards the star as a result of gravitational interactions with other "embryos" of the planets.
Recent observations of forming stars and protoplanetary disks that contradict this idea have led Bailey to formulate an alternative theory in which "hot Jupiters" could form directly next to a star.
Their "embryos", as noted by the planetary scientist, are tens and hundreds of "super-earths" - large rocky objects, whose mass exceeds that of the earth, appearing inside the primary nebula in the first moments of the life of the star. Almost all of them will subsequently be thrown out of the stellar system, but some of them are large enough to quickly collect all the surrounding gas and dust reserves and turn into a gas giant.
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As Batygin and Bailey found out, the planets that have arisen in this way will have several distinctive features at once, allowing them to be distinguished from the "hot Jupiters" - migrants. In particular, their mass will be in a special way related to where they are located in the orbit. In addition, many of them must revolve around the star, not alone, but in the company of one or more "super-earths".
Similar features, according to planetary scientists, have a significant part of the already discovered "hot Jupiters". It is likely that they were not born on the outskirts of protoplanetary disks, but directly next to the stars. This, in turn, indicates that not all planetary families arise in the same way as the solar system, which will complicate the assessment of their habitability and the search for extraterrestrial life.