Saturday, October 1, 2022

Astronomers make unprecedented detection of clouds on distant exoplanets

Using data from several telescopes, scientists have detected clouds on a gas giant exoplanet about 520 light-years from Earth. The observations were so detailed, they even understood the height of the clouds and the composition of the upper atmosphere with the greatest accuracy.

It is this work that will help us better understand exoplanet atmospheres – and look for worlds that have favorable conditions for life, or biosignatures in their spectra. We’re also getting closer to producing weather reports for distant alien worlds.

The exoplanet in question is WASP-127b, discovered in 2016. It is a hot and therefore bloated animal, orbiting so close to its star that its year is just 4.2 days. The exoplanet is 1.3 times the size of Jupiter, but only 0.16 times the mass of Jupiter.

This means that its atmosphere is somewhat thin and weak – perfect for trying to analyze its contents based on the light emanating from the exoplanet’s host star.

To do this, a team of researchers led by astronomer Romain Allart of the Université de Montréal in Canada used infrared data from the space-based Hubble Space Telescope, and optical data from the ESPRESSO instrument on the ground-based Very Large Telescope to peer into the universe. added for. At different altitudes in WASP-127b’s atmosphere.

“At first, as previously detected in this type of planet, we detected the presence of sodium, but at a much lower altitude than we expected,” Allart said.

“Second, there were strong water vapor signals in the infrared but none at visible wavelengths. This implies that water vapor at lower levels is being probed by clouds that are opaque at visible wavelengths but transparent in the infrared.”

Determining the composition of exoplanetary atmospheres is a difficult task. This is because we cannot directly observe most exoplanets; We infer their presence based on the effects they have on their host stars. One of these is dimmer and brighter – when the exoplanet passes between us and the star, the light from the star is reduced, just a little.

If it does this regularly enough times, it’s one of the telltale signs of an orbiting exoplanet. And we may use this information in other ways as well. When light from a star passes through an exoplanet’s atmosphere, the wavelengths in the spectrum can be absorbed by or by different elements. We call these signature absorption lines, and we can decode them to see what’s in that environment.

Compared to the wasp-127b solar system. (David Ehrenreich/Université de Geneve, Romain Alart/Université de Montréal)

That’s what Allart and his team did, using high-resolution absorption data to narrow down the height of the clouds to a surprisingly low cloud layer with atmospheric pressures between 0.3 and 0.5 millibars.

“We don’t know the composition of clouds yet, except that they’re not made of water droplets on Earth,” Allart said.

“We are also puzzled as to why sodium is found in an unexpected location on this planet. Future studies should help us understand more not only about atmospheric composition, but about WASP-127b, which It is proving to be an attractive place.”

The team’s analysis also found some strange things about how WASP-127b orbits its host star. In the Solar System, where things are arranged, all the planets orbit in a more or less flat plane around the Sun’s equator, in the direction of the Sun’s rotation. This is because of the way the Solar System was formed, from a disk of material swirling around in the baby Sun.

WASP-127b orbits not only in the opposite direction of its star’s rotation, but at a very pronounced angle, roughly around the star’s poles. The system is thought to be about 10 billion years old, which means that something strange is definitely going on in that particular neighborhood.

“Such alignment is unexpected for a hot Saturn in an old stellar system and may be due to an unknown companion,” Allart said.

“All these unique features make WASP-127b a planet that will be studied very intensively in the future.”

research was published in astronomy and astrophysics, and presented at the 2021 Europlanet Science Congress.


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