Swiss space telescope delivers first results on ‘extreme’ exoplanet

WASP-189b is an exoplanet orbiting the star HD 133112, one of the hottest stars known to have a planetary system. Because it is so hot, the star appears blue and not yellow-white like the sun. © ESA ESA

Eight months after the CHEOPS telescope started its journey into space, scientists have published their first results: an in-depth analysis of the exoplanet WASP-189b, one of the most extreme planets in the universe.

The telescope is travelling on board the satellite CHEOPSExternal link (CHaracterising ExOPlanet Satellite) as part of a three-year mission to study exoplanets.

The first exoplanet to be surveyed by the CHEOPS telescope is known as WASP-189b. It is orbiting the star HD 133112, one of the hottest stars known to have a planetary system, scientists say.

“The WASP-189 system is 322 light-years away and located in the constellation Libra (the weighing scales),” explained Monika Lendl from the University of Geneva in a statementExternal link on Monday.

“WASP-189b is especially interesting because it is a gas giant that orbits very close to its host star. It takes less than three days for it to circle its star, and it is 20 times closer to it than Earth is to the Sun.”

The planet is over one-and-a-half times as big as Jupiter, the largest planet in the Solar system.

Planets like WASP-189b are unusual, Lendl said.

“They have a permanent day side, which is always exposed to the light of the star, and, accordingly, a permanent night side,” she explained. “Based on the observations using CHEOPS, we estimate the temperature of WASP-189b to be 3,200° Celsius. Planets like WASP-189b are called ‘ultra-hot Jupiters’. Iron melts at such a high temperature, and even becomes gaseous. This object is one of the most extreme planets we know so far.”

The planet is not visible as it is too far away and too close to its host star, so scientists have to rely on indirect methods like the CHEOPS telescope, which uses precise brightness measurements.

‘More to come’

Willy Benz, professor of astrophysics at the University of Bern and head of the CHEOPS consortium, said he was delighted about the findings.

“These observations demonstrate that CHEOPS fully meets the high expectations regarding its performance,” he declared. “We are expecting further spectacular findings on exoplanets thanks to observations with CHEOPS. The next papers are already in preparation.”

The new study and results have been accepted for publication in the journal Astronomy & Astrophysics.

Exoplanets – planets outside the Solar system – were first found in 1995 by two Swiss astronomers, Michel Mayor and Didier Queloz, who last year were awarded the Nobel Prize for this discovery.

CHEOPS was developed as part of a partnership between the European Space Agency (ESA) and Switzerland. The joint mission is led by the University of Bern, in collaboration with the University of Geneva.

Over 100 scientists and engineers from 11 European states were involved in constructing the satellite over five years. The Science Operations Center of CHEOPS is located at the observatory of the University of Geneva.