With New Space Telescope, Astronomers Find One of the Most Extreme Planets in Universe

Bigger than Jupiter, a three-day orbit around its star and a permanent day side with temperatures hot enough to melt iron into a gas.

Infographic of the WASP 189 system (Courtesy of the European Space Agency)

(CN) — A European space telescope designed to gather information on planets beyond our solar system has uncovered the secrets of one such planet, revealing on Monday an extreme world with a permanent day and night side and surface temperatures hot enough to melt iron.

Last December, Switzerland and the European Space Agency launched the space telescope CHEOPS (Characterizing Exoplanets Satellite) to study exoplanets, planets that exist far beyond the gravitational reach of our sun.

One of the exoplanets targeted for study, WASP-189b, has been discovered to be an incredible world of extremes according to a new study published in the journal Astronomy & Astrophysics.

“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 for it to circle its star, and it is 20 times closer to it than Earth is to the Sun,” said lead author Monika Lendl in a statement.

Lendl said the exoplanet is “more than one and a half times as large as Jupiter” and orbits the extremely hot star HD 133112, a rarity according to the astronomer.

She said exoplanets like WASP-189b are “very exotic” due to their unique characteristics.

“They have a permanent day side, which is always exposed to the light of the star, and, accordingly, a permanent night side,” she said. “Based on the observations using CHEOPS, we estimate the temperature of WASP-189b to be 3,200 degrees Celsius [5,792 degrees Fahrenheit]. Planets like WASP-189b are called ‘ultra-hot Jupiters.’ Iron melts at such a high temperature, and even becomes gaseous. This object is one of the most extreme planets we know so far.”

WASP-189b is 322 light-years from Earth and located in the Libra constellation, which makes it difficult to observe, Lendl noted.

“We cannot see the planet itself as it is too far away and too close to its host star, so we have to rely on indirect methods,” she said.

To accomplish this, CHEOPS utilizes brightness measurements and can observe the star’s brightness as being fainter when the exoplanet passes in front of it.

“Because the exoplanet WASP-189b is so close to its star, its dayside is so bright that we can even measure the ‘missing’ light when the planet passes behind its star; this is called an occultation. We have observed several such occultations of WASP-189b with CHEOPS,” she said. “It appears that the planet does not reflect a lot of starlight. Instead, most of the starlight gets absorbed by the planet, heating it up and making it shine.”

Additionally, the telescope has been able to pick up characteristics of the star the exoplanet orbits around.

“We also found that the transit of the gas giant in front of its star is asymmetrical. This happens when the star possesses brighter and darker zones on its surface,” said Willy Benz, astrophysics professor at the University of Bern in Switzerland. “Thanks to CHEOPS data, we can conclude that the star itself rotates so quickly that its shape is no longer spherical; but ellipsoidal. The star is being pulled outwards at its equator.”

Benz said “only a handful of planets are known to orbit such hot stars.”

More than a hundred engineers and scientists developed the telescope over a period of five years. According to Benz, that work is already paying off.

“We are expecting further spectacular findings on exoplanets thanks to observations with CHEOPS. The next papers are already in preparation,” he said.

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