CHEOPS keeps its promise: observations with the space telescope have revealed details of the exoplanet WASP-1
Eight months after the CHEOPS space telescope mission began, the first scientific publication using CHEOPS data was published. CHEOPS is ESA’s first mission dedicated to characterizing known exoplanets, those stars orbiting outside the solar system. Exoplanets 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 partnership between ESA and Switzerland. Under the leadership of the University of Bern and ESA, a consortium of over 100 scientists and engineers from 11 European countries was involved in the construction of the satellite over a five-year period. CHEOPS Science Operations Center is located at the Geneva University Observatory.
Using data from CHEOPS, scientists recently conducted a detailed study of the exoplanet WASP-189b. The results have just been accepted for publication in the journal Astronomy and astrophysics. Willy Benz, professor of astrophysics at the University of Bern and head of the CHEOPS consortium, said: “These observations show that CHEOPS fully meets the high expectations regarding its performance.”
One of the most extreme planets in the universe
WASP-189b, the target of CHEOPS observations, is an exoplanet orbiting the star HD 133112, one of the hottest stars known to have a planetary system. “The WASP-189 system is 322 light-years away and is in the constellation of Libra (the balance),” explains Monika Lendl, lead author of the study at the University of Geneva and member of the National Competence Center in Research PlanetS .
“WASP-189b is particularly interesting because it is a gas giant that orbits very close to its host star. It takes less than three days to circle its star, and is 20 times closer to the star than Earth is at. Sunshine. “, Says Monika Lendl. The planet is more than 1.5 times larger than Jupiter, the largest planet in the solar system.
Monika Lendl further explains that planetary objects like WASP-189b are very exotic: “They have a permanent day side, which is always exposed to the star’s light, and consequently a permanent night side.” This means that its climate is completely different from that of the gas giants Jupiter and Saturn in our solar system. “Based on observations using CHEOPS, we estimate the temperature of WASP-189b to be 3,200 degrees Celsius. Planets like WASP-189b are called” ultra-hot Jupiter. Iron melts at such a high temperature and even becomes gaseous. This object is one of the most extreme planets we know of so far, “says Lendl.
Extremely accurate brightness measurements
“We can’t see the planet itself because it’s too far and too close to its host star, so we have to rely on indirect methods,” says Lendl. For this, CHEOPS uses extremely precise brightness measurements: when a planet passes in front of its star as seen from Earth, the star appears fainter for a short time. This phenomenon is called transit. Monika Lendl says, “Because the exoplanet WASP-189b is so close to its star, its day side is so bright that we can even measure the ‘missing’ light when the planet passes behind its star; this is called occultation. We have observed many of these occultations of WASP-189b with CHEOPS. It appears that the planet does not reflect much starlight. Instead, most of the starlight is absorbed by the planet, heating it and causing it to glow. ”
Researchers believe the planet is not very reflective because there are no clouds present on its day side. “This is not surprising, as theoretical models tell us that clouds cannot form at such high temperatures,” Lendl says.
Willy Benz says: “We also found that the gas giant’s transit in front of its star is asymmetrical. This happens when the star has brighter and darker areas on its surface. Thanks to CHEOPS data, we can conclude that the star itself rotates like this. quickly that its shape is no longer spherical, but ellipsoidal. The star is pulled outward to its equator. “
The star around which WASP-189b orbits is very different from the sun. Monika Lendl says: “The star is considerably larger and more than 2000 degrees Celsius hotter than our Sun. Because it is so hot, the star appears blue and not yellow-white like the sun.”
Willy Benz says: “Only a handful of planets are known to orbit such hot stars and this system is by far the brightest.” Consequently, it constitutes a reference point for further studies. “We expect further spectacular discoveries on exoplanets from observations with CHEOPS. The next documents are already in preparation.”
How the European CHEOPS satellite will improve the hunt for exoplanets
M. Lendl et al, The diurnal and asymmetrical warm transit of WASP-189 b as seen by CHEOPS, Astronomy and astrophysics (2020). DOI: 10.1051 / 0004-6361 / 202038677
First study with satellite data on exoplanets describes one of the most extreme planets in the universe (2020, September 28)
recovered on September 28, 2020
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