What is WASP-189 b? Study finds 'hot Jupiter' exoplanet that can vaporize metals like iron orbiting blue star
One of the most extreme alien worlds is just 322 light-years away and could be the most hostile exoplanets — it is ultra-hot, where temperatures can turn metals like iron into gases. What is more, the exoplanet orbits one of the hottest stars known: blue stars. The findings are a part of a new study.
The exoplanet in question is WASP-189 b. It is dubbed in the category hot Jupiter due to the similarities it shares with a gas giant like Jupiter. However, it is close to its star, about 20 times closer to its star than Earth is to the Sun. "Only a handful of planets are known to exist around stars this hot, and this system is by far the brightest," says Monika Lendl of the University of Geneva, Switzerland, lead author of the new study. "WASP-189b is also the brightest hot Jupiter that we can observe as it passes in front of or behind its star, making the whole system really intriguing."
Lendl and her colleagues also learned about the blue star: it is not perfectly round and is cooler at its equator than at the poles. Stars get their color from their temperatures — the hottest appears blue while the coolest is red.
The discovery was made possible, thanks to the European Space Agency's (ESA) exoplanet mission named Cheops. Launched in December, the satellite has been spying on known exoplanets to gain an understanding of how alien worlds form and evolve.
Using Cheops, the team looked for a change in light as exoplanets orbit their stars. In other words, they can cause a drop in brightness when an exoplanet passes behind its star. "As the planet is so bright, there is actually a noticeable dip in the light we see coming from the system as it briefly slips out of view," explains Lendl. "We used this to measure the planet’s brightness and constrain its temperature to a scorching 3200 degrees C." Such high temperatures vapourize metals, making it inhospitable for life, says the team.
Cheops revealed more details about WASP-189 b, including that it is almost 1.6 times the radius of Jupiter. Further, it has an inclined orbit, which means it's closer to the star’s poles than its equator. The tilt suggests the hot exoplanet formed further away from its star and was later pushed closer at some point. Researchers suspect this could either be due to multiple planets in a system or the influence of a star.
There is more. The exoplanet is tidally locked to its star, meaning only one side of the object faces the star. "They have a permanent dayside, which is always exposed to the light of the star, and, accordingly, a permanent night side," Lendl said. "This object is one of the most extreme planets we know so far."
Cheops will do more follow-up studies on other known exoplanets. "It will search for transits of planets that have been discovered from the ground, and, where possible, will more precisely measure the sizes of planets already known to transit their host stars," says Kate Isaak, Cheops project scientist at ESA. "By tracking exoplanets on their orbits with Cheops, we can make a first-step characterization of their atmospheres and determine the presence and properties of any clouds present."
The findings are published in Astronomy & Astrophysics.