Astronomers Discover the “Thermometer-Molecule” on an Exoplanet

Astronomers have confirmed the presence of chromium hydride (CrH) in the atmosphere of a hot Jupiter exoplanet for the first time. This relatively rare molecule is temperature-sensitive and can be used as a “thermometer.”

A hot Jupiter as imagined by an artist. Source: ESO/M. Kornmesser

The discovery was made during the study of the exoplanet WASP-31b, which orbits a red dwarf located 1,300 light-years away from Earth. This exoplanet is a hot Jupiter characterized by very low density. With a radius 1.55 times that of Jupiter and a mass only 0.48 times that of Jupiter, it falls into the category of low-mass hot Jupiters.

By analyzing spectroscopic observations of WASP-31b by Gemini North and VLT telescopes, the team of astronomers managed to confirm the presence of chlorine hydride in the exoplanet’s atmosphere.

Chlorine hydride is noteworthy for existing within a temperature range of 1000°C to 2000°C. At higher temperatures, only chromium is observed, while at lower temperatures, chlorine hydride transforms into other substances. In our Solar System, this molecule is only present in sunspots.

WASP-31b fits perfectly within the required temperature range. Its equilibrium temperature is 1200°C. As of now, this is the first exoplanet in whose atmosphere the presence of chlorine hydride has been confirmed. According to astronomers, this finding offers the potential to use this temperature-sensitive molecule as a “thermometer” to determine the temperature and other parameters of exoplanets, brown dwarfs, and cold stars.

Earlier, we reported on astronomers discovering a brown dwarf hotter than our Sun.

Based on materials from