Astronomers have tracked down an extreme binary system made up of two very old objects at a distance of 457 light-years from us. The first of them is red dwarf with a size of 17.6 percent of the radius and 13.4 percent of the mass of our Sun. The second object in the pair is faintly glowing (probably) brown dwarf – a substellar object whose mass is on the boundary between a star and a planet. According to astronomers, the brown dwarf is roughly the same size as Jupiter and 20% less massive.
But the size and mass of the two objects of the binary system are not what most interested the scientist. What is interesting is the distance that separates the two objects from each other and thus their orbital period. Both objects orbit each other in such close proximity that they complete one orbit in 1.9 Earth hours. The system was given a breakneck designation ZTF J2020+5033 and experts hope that its research and eventual discovery of the mechanism that brought the objects in question so close to each other could contribute to the understanding of the evolution of star systems.
Dangerous proximity
Finding a brown dwarf isn’t exactly easy. Although some estimates suggest that there could be between 25 and 100 billion brown dwarfs in the Milky Way alone, scientists only know about two thousand of these “failed stars” so far, with the vast majority of them found alone in space. However, this is not the case for the brown dwarf from the ZTF J2020+5033 system. Its proximity to the parent star is even a record – the hitherto least known system of a star and a brown dwarf was, according to scientists, seven times larger. The two objects are so close to each other that their entire binary system could comfortably fit inside our Sun. In any case, the question is how something like this could have arisen.
Kareem El-Badri from the American Caltech and his colleagues believe that the ZTF J2020+5033 system in its current form simply could not have formed. According to them, both objects originally had to be much larger and their orbits were also larger. Research conclusions describing a study that has not yet been peer-reviewed.
Death brake
Researchers believe that the present-day appearance of the ZTF J2020+5033 system is largely due to a “magnetic braking” mechanism (magnetic braking). In this case, the material ejected by the star can capture its magnetic field, as a result of which the star’s rotation slows down for some time. Scientists compare the magnetic braking mechanism to a figure skater who spreads his arms during a pirouette. In the case of a binary system, this effect is additionally amplified by the magnetic field of the second object. The rotation of both objects slows down and the two space objects gradually approach each other.
TIP: Is a brown dwarf more of a star or a planet?
According to the models, after overcoming the Roche limit, the brown dwarf should be torn apart by the gravitational force of its stellar partner. Under normal circumstances, this should happen in about 1.3 billion years. However, if the process of convergence of the two objects continues, the extinction of the brown dwarf may occur much earlier – perhaps within a few tens of millions of years.
2023-08-10 08:22:01
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