ESA’s exoplanet observer reveals strange ‘ultra-hot Jupiter’

This so-called "ultra-hot Jupiter" named WASP-189 b sits around 20 times closer to its star than Earth does to the Sun, and completes a full orbit in just 2.7 days, according to a paper accepted for publication by the journal Astronomy & Astrophysics.

London: European Space Agency’s new exoplanet mission called Cheops has found one of the hottest and most extreme extra-solar planets ever discovered.

This so-called “ultra-hot Jupiter” named WASP-189 b sits around 20 times closer to its star than Earth does to the Sun, and completes a full orbit in just 2.7 days, according to a paper accepted for publication by the journal Astronomy & Astrophysics.

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Hot Jupiters, as the name suggests, are giant gas planets a bit like Jupiter in our own Solar System; however, they orbit far, far closer to their host star, and so are heated to extreme temperatures.

The researchers determined that the planet is extremely hot, at about 3,200 degrees Celsius.

At such temperatures, even metals such as iron melt and turn to gas, making the planet a clearly uninhabitable one.

“Only a handful of planets are known to exist around stars this hot, and this system is by far the brightest,” said lead author of the new study Monika Lendl of the University of Geneva, Switzerland.

“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.”

The finding demonstrates Cheops’ ability to shed light on the universe around us by revealing the secrets of these alien worlds.

Launched in December 2019, Cheops (the Characterising Exoplanet Satellite) is designed to observe nearby stars known to host planets.

By precisely measuring changes in the levels of light coming from these systems as the planets orbit their stars, Cheops can initially characterise these planets — and, in turn, increase understanding of how they form and evolve.

The researchers used Cheops to observe WASP-189 b as it passed behind its host star — an occultation.

“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,” explained Lendl.

“We used this to measure the planet’s brightness and constrain its temperature to a scorching 3200 degrees C.”

This makes WASP-189 b one of the hottest and most extreme planets, and entirely unlike any of the planets of the solar system.