An artist’s impression of a hot-Jupiter exoplanet. Image credit: ESA / ATG Medialab / CC BY-SA 3.0 IGO.
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.
“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.”
They supplemented the GRACES data with archival data taken in 2017, which was not intended to look for metal hydrides.
“Part of our data for the paper was old data that was on the very edge of the data set. You wouldn’t have looked for it,” Dr. Flagg said.
“I’m hoping that the paper will encourage other researchers to look in their data for chromium hydride and other metal hydrides.”
“We think it should be there. Hopefully we’ll get more data that will be suitable for looking for chromium hydride and eventually build up a sample size to look for trends.”
Source: Sci News