Europe's CHEOPS satellite, which was launched last December, has revealed details about its first exoplanet: an extreme world, one of the hottest planets ever studied, where even metals like iron would vaporize and turn into gas .
The planet, named WASP-189b, is of a type known as ultra hot Jupiter because it is a gas giant like Jupiter and (you guessed it) is ultra hot.
The planet orbits its star 20 times closer than Earth to the Sun and moves in a year that is just 2.7 days. Not only is it orbiting extremely close to its star, but that star itself is incredibly hot and over 2,000 degrees Celsius hotter than the sun. In fact, the star is so hot that it appears to glow blue.
It was the extreme brightness of the star that enabled astronomers to see the planet, as lead author Monika Lendl of the University of Geneva in Switzerland explained: “Since the planet is so bright, there is actually a noticeable drop in light that we see out of the system as it briefly slips out of view. We used this to measure the brightness of the planet and keep its temperature to a scorching 3,200 degrees Celsius. "
Artist's impression of the exoplanet WASP-189b orbiting its host star. The system was observed by ESA's Cheops exoplanet mission to determine key features. For example, the host star is larger and more than 2000 degrees hotter than our own sun and therefore appears to glow blue. ESA
The whole system is hot, bright and unusual. "It is known that only a handful of planets exist around such hot stars, and this system is by far the brightest," said Lendl. "WASP-189b is also the brightest hot Jupiter we can observe as it passes in front of or behind its star, which makes the whole system really fascinating."
In addition to the hot planet, the star in this system has some interesting properties that have caught the attention of researchers. "We also saw that the star itself is interesting – it's not perfectly round, but larger and cooler at its equator than at the poles, which makes the star's poles appear brighter," said Lendl. "It rotates so fast that it is pulled outwards at its equator! Contributing to this asymmetry is the fact that the orbit of WASP-189b is inclined. It does not move around the equator, but rather runs close to the Poles of the star. "
The information about the planet's inclined orbit was of particular interest as it suggests that at some point in its history it was influenced by other planets or another star, bringing it closer to its star. This could help solve the mystery of how these extremely hot gas giants form.
The results are published in the journal Astronomy & Astrophysics.