With the help of the 10.4-meter Gran Telescopio Canarias (GTC), European astronomers have detected methane in the atmosphere of the object WISE1810 for the first time. This is the closest T-class brown dwarf to Earth.
Brown dwarfs occupy an intermediate position between gas giants and stars. Their masses range from 13 to 80 Jupiter masses. This is enough to start some thermonuclear reactions involving deuterium and lithium. However, the mass of brown dwarfs is not enough to sustain long-term reactions involving ordinary hydrogen. This is why brown dwarfs do not reach a constant luminosity like stars, but shrink and dim.
Like stars, brown dwarfs fall into a number of spectral classes. One of these is known as T dwarfs. It includes the coldest and least luminous brown dwarfs, whose effective surface temperatures lie between 230 °C and 1230 °C.
Studying T dwarfs can help astronomers better understand the difference between objects on the boundary separating different types of celestial bodies. However, while many brown dwarfs have been discovered to date, T dwarfs are not so common — only about 400 have been identified.
The closest of these, known as WISE1810, is 29 light-years away from Earth. Its radius is about 0.65 the radius of Jupiter, and its mass is about 17 times that of Jupiter. Previous observations of WISE1810 have revealed that its atmosphere is dominated by hydrogen and water vapor. However, it showed no traces of methane, which is the defining molecule for T-dwarfs.
The situation has changed with the recent publication of a new study by an international team of astronomers using GTC. They were able to detect methane in the atmosphere of WISE1810 and estimate its temperature, which is about 770 °C. Scientists have also managed to measure the speed of the brown dwarf. This helped to determine that, despite its very low metallicity, it is most likely associated with the Milky Way’s thick disk rather than the halo.
Earlier we reported on the discovery of potassium cyanide in the atmosphere of a brown dwarf.
According to Phys.org
