A newly discovered exoplanet could have rain clouds

(CNN) – Scientists discovered an exoplanet located 90 light-years from Earth with an intriguing atmosphere that could contain clouds of water.Exoplanets are planets located outside of our solar system. This exoplanet, called TOI-1231 b, makes a complete orbit around its star every 24 Earth days.

The planet orbits a red dwarf, or M-type, star known as NLTT 24399, which is smaller and dimmer than stars like our Sun.

The planet’s discovery is detailed in a new study to be published in a future issue of the journal. The Astronomical Journal.

“Although TOI 1231 b is eight times closer to its star than Earth is to the Sun, its temperature is similar to that of Earth, thanks to the fact that its host star is colder and less bright,” said the co-author of the study Diana Dragomir, assistant professor in the Department of Physics and Astronomy at the University of New Mexico, in a statement.

“However, the planet itself is actually larger than Earth and slightly smaller than Neptune, we could call it a sub-Neptune.”

Why could it have clouds

The researchers were able to determine the radius and mass of the planet, which helped them calculate its density and infer its composition.

The exoplanet has a low density, suggesting that it is a gaseous planet rather than a rocky one like Earth, but scientists still do not know for sure the composition of the planet or its atmosphere.

“TOI-1231 b is quite similar in size and density to Neptune, so we think it has an equally large gaseous atmosphere,” said lead study author Jennifer Burt, a NASA Jet Propulsion Laboratory postdoctoral fellow at Pasadena, California.

“TOI1231b could have a large hydrogen or hydrogen-helium atmosphere, or a denser water vapor atmosphere,” said Dragomir.

“Each of them would point to a different origin, allowing astronomers to understand if and how planets form differently around M dwarfs, compared to planets surrounding our Sun, for example.” .

The researchers believe that TOI-1231 b has an average temperature of 60 ° C, making it one of the coldest of the small exoplanets available to study its atmosphere.

“Compared to most of the transiting planets detected so far, which typically have scorching temperatures of many hundreds or thousands of degrees, TOI-1231 b is positively icy,” said Burt.

The colder the exoplanet, the more likely it is to have clouds in its atmosphere.

The similarly sized exoplanet K2-18 b, discovered in 2015, was recently observed in more detail, and the researchers found evidence of the presence of water in its atmosphere.

«TOI-1231 b is one of the only other planets we know of in a similar size and temperature range, so future observations of this new planet will allow us to determine how common (or rare) it is for water clouds to form around of these temperate worlds, “Burt said in a statement.

This makes TOI-1231 b the perfect candidate for observations by the Hubble Space Telescope, or the James Webb Space Telescope, which is scheduled to be deployed in October. The Webb will have the ability to peer into the atmospheres of exoplanets and help determine their composition. And Hubble is scheduled to observe the exoplanet later this month.

The search for exoplanets

Burt, Dragomir and their colleagues discovered the planet thanks to data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The planet hunter satellite, launched in 2018, observes different areas of the sky at the same time for 28 days. So far, TESS has helped scientists find large and small exoplanets that orbit stars like our Sun, as well as the smaller M-dwarf stars. These tiny stars are common in the Milky Way.

When a planet crosses in front of its star during its orbit, it blocks a certain amount of light. This is called a transit, and it’s one of the ways astronomers search for exoplanets using missions like TESS.

Since M-dwarf stars are smaller, the amount of light blocked by an orbiting planet is greater, making the transit more detectable. Scientists look for at least two transits before determining if they have found an exoplanet candidate. Subsequent observations were made with the Planet Finder spectrograph of the Magellan telescopes at the Las Campanas Observatory in Chile.

“One of the most intriguing results of the last two decades of exoplanet science is that, so far, none of the new planetary systems we have discovered looks anything like our own solar system,” said Burt.

“This new planet we just discovered is still strange, but it is one step closer to resembling our neighboring planets in some way.”