A group of astronomers made a groundbreaking discovery by detecting hydrogen cyanide and acetylene in the atmosphere of a brown dwarf known as Wise J045853.90+643451.9, which is located just 30 light years away from Earth. Brown dwarfs are celestial bodies that fall in between planets and stars in terms of mass, with a range of 13-80 times greater mass than Jupiter but not enough to sustain nuclear reactions like stars. As a result, brown dwarfs gradually cool over time.
The pair of brown dwarfs studied belong to a specific subclass called T-CALIMS, which are the coldest and dimmest members of the brown dwarf family, with temperatures ranging from 500 to 1500 kelvins. These particular brown dwarfs have been classified as T8.5 and T9 types, with surface temperatures of 600 and 500 kelvins respectively, significantly cooler than the Sun. The two celestial bodies orbit each other at a distance roughly equivalent to the distance between the Sun and Jupiter.
A team of scientists led by Elizabeth Matthews from the Max Planck Institute of Astronomy in Heidelberg conducted observations of Wise J045853.90+643451.9 using the MRS medium-resolution spectrometer as part of the Miri infrared device on the James Webb telescope. Their analysis revealed the absence of clouds in the atmosphere of the brown dwarfs, but a rich chemical composition including methane, carbon dioxide, carbon monoxide, water, and ammonia.
Of particular interest was the presence of hydrogen cyanide and acetylene in the brown dwarfs’ atmospheres, compounds not typically found in such objects. Acetylene is more commonly found in gas giants like Jupiter and Saturn, while hydrogen cyanide is rare in the solar system and is often found in interstellar clouds. The discovery of these compounds suggests the existence of complex chemical processes at low temperatures.
Further observations allowed scientists to determine the physical parameters of the two brown dwarfs, revealing their sizes to be approximately 0.81 times the radius of Jupiter. The total mass of the brown dwarf pair is equivalent to 132 Jupiters. The next step for astronomers is to search for similar chemical compounds in the atmospheres of other stars with similar temperatures.