A blazing world, where metallic clouds spew titanium drops, is the most reflective planet ever observed outside our solar system, astronomers said on Monday. Located 260 light-years from Earth, this strange world reflects 80 percent of the light from its host star, according to new observations from Europe’s exoplanet probe Cheops.

This makes it the first exoplanet to be brighter than Venus, the brightest object other than the Moon in our night sky. First discovered in 2020, the Neptune-sized planet LTT9779b orbits its star in just 19 hours. Because it is so close, the side of the planet facing its star is 2,000 degrees Celsius hotter, which is considered too hot for cloud formation.

However, the LTT9779b seems to have them.

“It was really a puzzle,” said Vivienne Parmantier, a researcher at the Cote d’Azur Observatory in France and co-author of the new study in the journal. Astronomy and Astrophysics. The researchers later said that “we understood that we should think of this cloud formation in the same way as condensation that forms in the bathroom after a hot shower.”

Like hot water flowing over a bath, the scorching stream of metal and silicate that makes up the glass oversaturated LTT9779b’s atmosphere until metallic clouds formed, he said.

This is an artist’s drawing of exoplanet LTT9779b orbiting its host star. The planet is approximately the size of Neptune and reflects 80% of the light falling on it, making it the largest known “mirror” in the universe. This glow was discovered by ESA’s Cheops spacecraft thanks to detailed measurements of the amount of light coming from the planet’s star system. As the planet reflected starlight back to us, the amount of light reaching the Cheops instruments decreased slightly as the planet moved out of sight behind the star. This small drop can be measured due to the high accuracy of the detectors. Copyright: ESA

Survival in the “Neptune desert”

The planet, which is about five times the size of Earth, stands out in other respects as well. The previously discovered exoplanets orbiting their stars in less than 24 hours are either gas giants 10 times the size of Earth or rocky planets half the size of Earth. However, LTT9779b lives in a region called the “Neptune desert” where planets of this size should not exist.

“This is a planet that shouldn’t exist,” Parmentier said. “We expect the atmospheres of such planets to be blown away by the stars, leaving bare rocks behind.”

According to the European Space Agency’s Cheops project scientist Maximilian Gunther, the planet’s metallic clouds “act like mirrors”, reflecting light and preventing the atmosphere from swelling.

“It’s like a shield, like in the old Star Trek movies with shields around their ships,” he told AFP.

He added that the study marks an “important milestone” as it shows how a Neptune-sized planet could survive in the Neptune desert.

The European Space Agency’s Cheops space telescope was launched into Earth orbit in 2019 to study planets discovered outside our solar system. He measured LTT9779b’s reflectivity by comparing the light before and after it disappeared behind the exoplanet star. Source