The European Space Agency (ESA) has just announced that Cheops, the “CHaracterising ExOPlanet Satellite,” has discovered an “ultra-hot Jupiter” exoplanet. The exoplanet, dubbed WASP-189 b, orbits closely around a rapidly spinning blue star. The distant planet’s surface is so hot, the ESA says, that it could melt iron into gas.

The ESA described the discovery in a recent announcement. In the announcement, which comes via Gizmodo, the space agency says WASP-189 b is one of the hottest and “most extreme” planets ever discovered.

“Only a handful of planets are known to exist around stars this hot, and this system is by far the brightest,” Monika Lendl says in the announcement. Lendl, at the University of Geneva, Switzerland, led the team that discovered the exoplanet.

Astronomers have found an ultra-hot Jupiter orbiting a blue star.


Lendl and her colleagues discovered the ultra-hot Jupiter using the transit method. The transit method identifies exoplanets by measuring dips in the light coming from their parent stars as they pass by. But because WASP 189 b is so hot—it’s approximately 5,800 °F—it is also very bright. So bright, in fact, there’s a noticeable dip in the light we observe coming from WASP-189 during the brief period when the exoplanet slips behind it, but is still in view.

“WASP-189b is… 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 added. By measuring the difference in the light coming from WASP-189 as the hot Jupiter (which is 1.6 times the size of our Jupiter) passed, the astronomers were able to determine the latter’s brightness, and therefore its temperature.


Lendl and her team also found that WASP-189, which appears to glow blue, is unique itself. “[The] star’s not perfectly round, but larger and cooler at its equator than at the poles, making the poles of the star appear brighter,” Lendl says. Apparently the star is spinning so fast it’s being pulled outward at its middle.

Looking forward, the ESA says this is only the beginning for Cheops. The space telescope only opened its “eye” in January of this year, and began routine operations in April. “This first result from Cheops is hugely exciting…” Kate Isaak, Cheops project scientist, says in the press release. Isaak adds that this discovery “is early definitive evidence that the mission is living up to its promise in terms of precision and performance.”

Feature image: ESA