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Due to its proximity to its parent star, the day-side equilibrium temperature of ultra-hot Jupiter WASP-189b reaches 3,162 degrees Celsius (5,724 degrees Fahrenheit), according to an analysis of data collected by the CHEOPS mission (which characterizes the satellite ExOPlanet) of ESA.
An artist’s impression of an ultra-hot Jupiter. Image Credit: Sci-News.com.
Discovered in 2018, WASP-189b is a gas giant that transits the 730-million-year-old type A star WASP-189.
Also known as HD 133112, the host star is larger and more than 2,000 degrees Celsius hotter than the Sun, so it appears to glow blue.
WASP-189b is 20 times closer to its star than Earth is to the Sun, completing a full orbit in just 2.7 days.
“The WASP-189 planetary system is located 322 light years away in the constellation Libra,” said Dr. Monika Lendl, an astronomer at the University of Geneva.
“WASP-189b is especially interesting because it is a gas giant that orbits very close to its host star.”
“It takes less than 3 days to go around its star, and it is 20 times closer to it than Earth is from the Sun.”
“Only a few planets are known to exist around such hot stars, and this system is by far the brightest,” he added.
“WASP-189b is also the brightest hot Jupiter that we can observe when it passes in front of or behind its star, which makes the whole system really intriguing.”
WASP-189 planetary system key parameters. Image credit: ESA.
First, Dr. Lendl and his colleagues used CHEOPS to observe WASP-189b as it passed behind its star, an occultation.
“We use this to measure the brightness of the planet and limit its temperature to a scorching 3,162 degrees Celsius,” he said.
The astronomers then watched WASP-189b pass its star – a transit.
Transits can reveal a lot about the size, shape, and orbital characteristics of a planet. This was true for WASP-189b, which turned out to be larger than previously thought at nearly 1.6 times the radius of Jupiter.
“We also saw that the star itself is interesting: it is not perfectly round, but larger and cooler at its equator than it is at the poles, which makes the star’s poles appear brighter,” said Dr. Lendl.
“It spins so fast that it is being dragged out at its equator! Added to this asymmetry is the fact that the orbit of WASP-189b is tilted; It does not travel around the equator, but passes close to the star’s poles. “
“This first CHEOPS result is tremendously exciting: it is definitive initial evidence that the mission is delivering on its promise in terms of precision and performance,” said Dr. Kate Isaak, CHEOPS project scientist, ESA astronomer.
The findings will be published in the journal. Astronomy and Astrophysics.
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M. Lendl et al. 2020. The hot side and asymmetric traffic of WASP-189 b as seen by CHEOPS. AA, in press; doi: 10.1051 / 0004-6361 / 202038677
