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 data from CHEOPS was published. CHEOPS is the first ESA mission to characterize known exoplanets orbiting stars outside the solar system. Exoplanets were first found 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 direction of the University of Bern and the ESA, a consortium of more than 100 scientists and engineers from 11 European countries was involved in the construction of the satellite for five years. The CHEOPS Science Operations Center is located at the Observatory of the University of Geneva.
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 & 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 the CHEOPS observations, is an exoplanet orbiting 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 located in the constellation Libra (Libra),” explains Monika Lendl, lead author of the study at the University of Geneva and member of the National Center of Excellence for Research Planets.
“WASP-189b is particularly interesting because it is a gas giant orbiting very close to its host star. It takes less than three days to orbit its star, and it is 20 times closer to the star than Earth is to Sun “, says Monika Lendl. The planet is more than 1.5 times the size of 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 that is always exposed to the light of the star, and accordingly a permanent night side.” This means that the climate is completely different from that of the gas giants Jupiter and Saturn in our solar system. “Based on the observations made with 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 turns into a gas. This object is one of the most extreme planet that we know so far, “says Lendl.
Highly precise brightness measurements
“We cannot see the planet ourselves because it is too far away and too close to its host star. That is why we have to rely on indirect methods,” explains Lendl. For this purpose, CHEOPS uses high-precision brightness measurements: When a planet passes in front of its star as seen from Earth, the star appears weaker for a short time. This phenomenon is known as transit. Monika Lendl says: “Because the exoplanet WASP-189b is so close to its star, its daytime side is so bright that we can even measure the ‘missing’ light when the planet passes behind its star; this is called eclipse. We have observed several such occultations of WASP-189b with CHEOPS. It appears that the planet does not reflect much starlight. Instead, most of the starlight is absorbed, heated and made to glow by the planet. ”
The researchers believe that the planet is not very reflective because there are no clouds on its days. “This is not surprising, since theoretical models tell us that clouds cannot form at such high temperatures,” says Lendl.
Willy Benz says: “We have also determined that the transit of the gas giant in front of its star is asymmetrical. This happens when the star has lighter and darker zones on its surface. Thanks to CHEOPS data, we can conclude that the star itself is rotating so fast that its shape is no longer spherical but ellipsoidal. The star is pulled outwards at 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 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.” As a result, it forms a benchmark for further study. “Thanks to the observations with CHEOPS, we expect further spectacular results with exoplanets. The next work is already in preparation.”
How Europe’s CHEOPS satellite will improve exoplanet hunting
M. Lendl et al., The Hot Day and Asymmetric Transit of WASP-189b, Seen by CHEOPS, Astronomy & Astrophysics (2020). DOI: 10.1051 / 0004-6361 / 202038677
Provided by the University of Bern
Quote: First study with exoplanet satellite data describes one of the most extreme planets in the universe (2020, September 28), which was published on September 28, 2020 from https://phys.org/news/2020-09-exoplanet-satellite-extreme-planets – was retrieved. universe.html
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