The CHEOPS space telescope analyzes one of the most extreme planets in the universe

The first scientific publication using data from the CHEOPS satellite telescope was released eight months after launch.

CHEOPS is the first mission of the European Space Agency (ESA) to characterize known exoplanets. Exoplanets, or planets outside our solar system, were first discovered in 1995 by two Swiss astronomers, Michel Mayor and Didier Queloz, who received the Nobel Prize for this discovery last year. CHEOPS was developed as part of a collaboration between ESA and Switzerland. A consortium of over one hundred scientists and engineers from eleven European countries worked on the satellite for five years, led by the University of Bern and ESA. The CHEOPS Science Operations Center is housed in the Observatory of the University of Geneva.

Scientists recently conducted a detailed study of exoplanet WASP-189 using data from CHEOPS. who are preparing the results for publication in Astronomy & Astrophysics. “These observations indicate that CHEOPS fully meets the high expectations for its performance,” said Willy Benz, Professor of Astrophysics at the University of Bern and leader of the CHEOPS consortium.

CHEOPS offers highly accurate brightness measurements

When a planet passes in front of its star, the star appears dimmer as seen from Earth for a short time. Transit is a term for this phenomenon. When a planet passes in front of a star, the light it emits and/or reflects is momentarily blocked out by the principal. Occultation is the term for this phenomenon. ESA (European Space Agency)

WASP-189b, an exoplanet orbiting the star HD 133112, one of the hottest stars known to host a planetary system, is one of the outermost planets in the cosmos. It is the goal of the CHEOPS observations. “The WASP-189 system is located in the constellation of Libra (the Scales) and is 322 light-years away,” says Monika Lendl, lead author of the study and member of the National Center of Competence in Research PlanetS.

“WASP-189b is particularly intriguing because it is a gas giant orbiting its host star fairly closely. It orbits its star in less than three days and is 20 times closer to it than Earth is to the sun,” says Monika Lendl Planet, which is more than one and a half times the size of Jupiter, the largest planet in the solar system.

“They have a permanent day side, which is always exposed to the light of the star, and consequently also a permanent night side,” says Monika Lendl about planetary objects like WASP-189b. This means that its climate is radically different from that of our solar system’s gas giants, Jupiter and Saturn. “We estimate the temperature of WASP-189b to be 3,200 degrees Celsius based on CHEOPS measurements. “Ultra hot Jupiters” are planets like WASP-189b. At such a high temperature, iron melts and even turns into a gas. “This is one of the most extreme planets that we have discovered so far,” says Lendl.

Brightness measurements with the highest precision

“We can’t see the planet because it’s too far away and too close to its host star,” Lendl continues, “so we have to rely on indirect means.” CHEOPS does this through extremely accurate measurements of brightness: when a planet in front of its passes, the star appears dimmer for a short time as seen from Earth. Transit is a term for this phenomenon. “Because exoplanet WASP-189b is so close to its star, its dayside is so bright that we can even quantify the missing light as the planet passes behind its star; this is referred to as coverage,” says Monika Lendl. “With CHEOPS, we have seen three such occultations of WASP-189b,” explains Lendl. “It appears that the planet doesn’t reflect much light from the stars. Instead, the planet absorbs most of the starlight, which heats it up and makes it glow.” Since there are no clouds on the planet’s day side, the researchers believe that it is not extremely reflective: “This is not surprising, since clouds according to theoretical models cannot generate such high temperatures.”

The star is also unique.

“We also discovered that the transit of the gas giant in front of its star is asymmetrical.” “This happens when the star’s surface has lighter and darker zones,” says Willy Benz. “We can conclude from CHEOPS data that the star is rotating so fast that its shape no longer changes spherical, but elliptical.” “The star is pulled outwards at its equator,” adds Benz.

WASP-189b orbits a star that differs significantly from the Sonne differs. “The star is significantly larger and almost two thousand degrees hotter than our sun,” explains Monika Lendl. The star appears blue rather than yellow-white because it is so hot.” “Few planets are known to orbit such hot stars, and this system is the brightest from far,” says Willy Benz. It thus serves as a basis for future research.

“Based on the observations made with CHEOPS, we expect further remarkable results on exoplanets,” concludes Willy Benz. The following papers are already in progress.”