Two barely stars were found to be engaged in an eclipse. The discovery was made accidentally by astronomers searching for potentially habitable planets. The two objects involved are two brown dwarf stars. The study on the binary system was published in the journal Nature.
A brown dwarf is a type of substellar object occupying the mass range between the most massive gas giant planets and the lightest stars. Its mass is between approximately 13 and 75–80 times that of Jupiter. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth. It is debated whether brown dwarfs would be better defined by their formation processes rather than by their nuclear fusion reactions.
The two brown dwarf stars create a unique eclipse
While working on SPECULOOS, astronomers were observing 2M1510. At some point, they registered a decrease in its luminosity that lasted for 90 minutes. SPECULOOS is a project known as the Search for habitable Planets Eclipsing Ultra-cool Stars. The four m-diameter telescopes will be equipped with cameras sensitive in the near-infrared, the wavelength range in which ultra-cool stars and brown dwarf stars emit most of their light.
The astronomers were amazed to find that 2M1510 was part of a binary, being orbited by another of her kind. They are currently searching for Earth-sized exoplanets between around 1000 ultra-cool stars and brown dwarfs, so the eclipse wasn’t an easy catch. During the survey operation, each telescope observes one target for about ten nights. To observe 500 targets in the southern hemisphere, 1200 nights or five years are needed.
“We rapidly realized that we were probably looking at two eclipsing brown dwarfs, one passing in front of the other, a configuration which is much rarer than planetary systems,” said Artem Burdanov, the co-author of the study. It’s an important discovery, as brown dwarf stars represent the missing chain link between the smallest red dwarfs and giant Jupiters. This is only the second eclipsing binary brown dwarf found so far.