Evidence for dust at liquefied gas boundary on exoplanet WASP-31b

Evidence for dust at liquefied petroleum gas boundary on exoplanet WASP-31b

Artist impression of an exoplanet. Credit: ESA / ATG medialab, CC BY-SA 3.0 IGO

One of the characteristics that makes a planet fit for life is the presence of a weather system. Exoplanets are too far away to observe them directly, but astronomers can look for substances in the atmosphere that make a weather system possible. Researchers from SRON Netherlands Institute for Space Research and the University of Groningen have now found evidence on exoplanet WASP-31b for chromium hydride, which is at the corresponding temperature and pressure at the boundary between liquid and gas. The study was published in Astronomy & Astrophysics.

While space probes scan the planets and moons around our sun for extraterrestrial life, there are hundreds of billions of other stars in our galaxy, most of which are probably also surrounded by planets. These so-called exoplanets are too far to travel, but we can study them with our telescopes. Although the spatial resolution is usually insufficient to take a picture of an exoplanet, astronomers can still get a lot of information from the fingerprints that the atmosphere leaves behind in the light rays of the host.

From the fingerprints – so-called transmission spectra – astronomers deduce which substances are present in the atmosphere of an exoplanet. It may one day give an indication of foreign life. Or they can show that there is a condition of life, like a weather system. For the time being, however, this kind of research is limited to giant planets near their stars, called hot Jupiters. These planets are too hot to expect life, but they can already teach us a lot about how possible weather systems work. A research team from SRON Netherlands Institute for Space Research and the University of Groningen has now found evidence for a substance on the boundary between liquid and gas. On earth it is reminiscent of clouds and rain.

First author Marrick Braam and his colleagues found evidence in Hubble data for chromium hydride (CrH) in the atmosphere of the exoplanet WASP-31b. It is a warm Jupiter with a temperature of about 1 200 ° C in the twilight zone between day and night – the place where starlight moves through the atmosphere to the earth. And this is about the temperature at which chromium hydride changes from liquid to gas at the corresponding pressure in the outer layers of the planet, similar to the conditions for water on earth. “Chromium hydride could play a role in a possible weather system on this planet, with clouds and rain,” says Braam.

This is the first time that chromium hydride is found on a hot Jupiter and is therefore at the right pressure and temperature. Braam: “We must add that we only found chromium hydride using the Hubble Space Telescope. We did not see it in the data of the ground telescope VLT. There are logical explanations for this, but we therefore use the term evidence instead. proof. ”

When Hubble’s successor – the James Webb Space Telescope (JWST) – launches later this year, the team plans to use it for further investigation. “Hot Jupiters, including WASP-31b, always have the same side as their host,” says Michiel Min, co-author and SRON Exoplanets program leader. “We therefore expect a day side with chromium hydride in gaseous form and a night side with liquid chromium hydride. According to theoretical models, the large temperature difference creates strong winds. We want to confirm this with observations.”

Co-author Floris van der Tak (SRON / UG) says: “With JWST we are looking for chromium hydride on ten planets with different temperatures, to better understand how the weather systems on those planets depend on the temperature.”


Astronomers see unexpected molecules in exoplanet atmosphere


More information:
Marrick Braam, Floris FS van der Tak, Katy L. Chubb and Michiel Min, ‘Evidence for chromium hydride in the atmosphere of the hot Jupiter WASP-31b’, Astronomy & Astrophysics, 2021.

Provided by SRON Netherlands Institute for Space Research

Quotation: Evidence for the substance at the liquefied gas boundary on the exoplanet WASP-31b (2021, 3 February) obtained on 3 February 2021 from https://phys.org/news/2021-01-evidence-substance-liquid-gas-boundary- exoplanet .html

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