Astronomers identify the most reflective exoplanets

A hot, hot world where metallic clouds rain droplets of titanium is the most reflective planet ever seen outside our solar system, astronomers said.

This strange world, more than 260 light-years from Earth, reflects 80 percent of the light from its host star, according to new observations from Europe’s Khufu Space Telescope for Exoplanet Exploration.

This makes it the first exoplanet as bright as Venus, which is the brightest object in our night sky other than the Moon.

First discovered in 2020, a Neptune-sized planet called 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, which is too hot for clouds to form.

However, LTT9779b appears to have it.

“It was really a mystery,” said Vivian Parmentier, a researcher at France’s Côte d’Azur Observatory and co-author of a new study in the journal. Astronomy and astrophysics.

The researchers then “realised that we should think of this cloud formation in the same way that condensation forms in the bathroom after a hot shower,” he said in a statement.

Like running hot water in a shower, a scorching stream of metal and silicates — the material glass is made of — saturated LTT9779b’s atmosphere until metallic clouds formed, he said.

Survive the “Neptune Desert”

The planet, which is about five times the size of Earth, is an odd one in other ways.

The only exoplanets previously found to orbit their stars in less than 24 hours are either gas giants 10 times larger than Earth – or rocky planets half their size.

But LTT9779b lives in an area called the “Neptune Desert”, where no planets of its size are supposed to exist.

“It’s a planet that shouldn’t exist,” Parmentier said.

“We expect planets like this to have their atmospheres blown away by their star, leaving behind barren rocks.”

According to Maximilian Guenther, ESA’s Khufu project scientist, the planet’s metallic clouds “work like a mirror”, reflecting light away and preventing the atmosphere from being blown away.

“It’s a bit like shielding, like in the old Star Trek movies, where they have shields around their ships,” he told AFP.

He added that the research marks a “major milestone” because it shows how a Neptune-sized planet could survive in the Neptune desert.

The European Space Agency’s Khufu Space Telescope was launched into Earth’s orbit in 2019 on a mission to explore discovered planets outside our solar system.

Measured the reflectivity of LTT9779b by comparing the light before and after the exoplanet disappeared behind its star.