A binary system called ZTF J2020+5033 has been discovered, breaking records with its extremely tight rotation. The system is located just 457 light-years away and consists of a high-mass brown dwarf and a low-mass red dwarf that orbit each other in 1.9-hour orbits. This is the closest orbit a brown dwarf has ever found, making the distance between the two objects less than half the radius of the Sun. Brown dwarfs, which are among the types of stars and planets, are difficult to detect due to their small size and darkness. Only about 5,000 brown dwarfs have been identified in the Milky Way, and very few are found in nearby binary systems with other minor stars. The discovery of ZTF J2020+5033 could provide valuable information on the formation and evolution of these mysterious objects. The system’s red dwarf star is relatively small, only 17.6% of the Sun’s radius and 13.4% of the Sun’s mass. Brown dwarfs, on the other hand, are close to the upper mass limit for such objects, at 80.1 times the mass of Jupiter. The researchers believe the two objects were once much larger, suggesting they were at least five times apart. The tight orbit suggests that “magnetic braking” is an efficient process in this system, even in low-mass stars and brown dwarfs. Going forward, the trajectory of ZTF J2020+5033 is expected to continue to narrow. The brown dwarf, although smaller and lighter than the red dwarf, has a slightly higher surface gravity, causing it to suck up material from the red dwarf as they approach. This mass transfer is expected to happen within the next tens of millions of years. The discovery of ZTF J2020+5033 suggests that low-mass binaries up close like this may be relatively common, but the previous low light made them difficult to detect. However, with improved telescope technology, scientists may soon be able to identify more of these systems and study the magnetic brake in more detail.
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