Chromium hydride is often used to probe atmospheric temperatures and classify objects called brown dwarfs into spectral types because it’s abundant only in a narrow range between 1,200 and 2,000 K.
First discovered in 2011, WASP-31b is a so-called hot Jupiter exoplanet.
It has a mass of 0.5 times that of Jupiter and a radius of 1.5 Jupiter radii, making it one of the lowest density exoplanets known to date.
WASP-31b orbits the 1-billion-year-old F5-type star WASP-31 once every 3.4 days. The system is located about 1,305 light-years away in the constellation of Crater.
“Chromium hydride has no previous confirmed detections in any exoplanet, and this marks the first detection of a metal hydride from a high-resolution exoplanet spectrum,” said Cornell University astronomer Laura Flagg.
“The definitive detection of metal hydrides in WASP-31b is an important advancement in the understanding of hot giant planet atmospheres, although the discovery doesn’t give new information about the individual planet.”
The new study confirms WASP-31b’s equilibrium temperature at 1,400 K — in range for chromium hydride.
“Chromium hydride molecules are very temperature sensitive. At hotter temperatures you see just chromium alone. And at lower temperatures it turns into other things.”
“So there’s only a specific temperature range, about 1,200 to 2,200 Kelvin, where chromium hydride is seen in large abundances.”
“In our Solar System, the only detected occurrence of this molecule is in sunspots” the Sun is too hot (around 6,000 K on the surface) and all other objects are too cool.”
To analyze WASP-31b, Dr. Flagg and colleagues used high-resolution spectra from one new observation in March 2022 as part of the Exoplanets with Gemini Spectroscopy survey from Hawaii‘s Maunakea, using the Gemini Remote Access to the CFHT ESPaDOnS Spectrograph (GRACES).
They supplemented the GRACES data with archival data taken in 2017, which was not intended to look for…
Read the full article here