Maybe it won’t last, but researchers this week said they discovered a real planet beyond our solar system — a blazing hot world slightly larger than Neptune that orbits a Sun-like star every 19 hours and appears to be covered in metal. Clouds made of titanium and silicates reflect most of the light coming into space.
Written by Will Dunham
WASHINGTON — Astronomers say it’s a planet that probably shouldn’t exist.
This week researchers said they discovered a real planet beyond our solar system, a hotter world slightly larger than Neptune that appears to be shrouded in clouds of metal made of titanium and silicates that orbit a Sun-like star every 19 hours. Most incoming light is back into space.
“It’s a giant mirror in space,” said astronomer James Jenkins, of the University of Diego Portales and the Center for Excellence in Astrophysics and Associated Technologies (CATA) in Chile, and co-author of the research, published in the journal Astronomy and Astrophysics.
It reflects 80% of incoming light, making it the most reflective object in the universe. The brightest object in Earth’s night sky besides the Moon, Venus is the most reflective object in our solar system and is surrounded by clouds of toxic sulfuric acid. Venus reflects 75 percent of incoming light. Earth reflects about 30%.
Named LTT9779b, the planet and its star are located in our Milky Way galaxy in the direction of Sculptor, about 264 light-years from Earth. A light year is the distance light travels in one year, which is 5.9 trillion miles (9.5 trillion kilometers).
The planet is 4.7 times the diameter of Earth, and it orbits very close to its star – closer than the distance to the Sun of our solar system’s innermost planet, Mercury, and 60 times closer than Earth’s orbit. With scorching solar radiation from its star, its surface temperature is about 3,270 degrees Fahrenheit (1,800 degrees Celsius), hotter than molten lava.
According to the researchers, because its star is so close, it’s a wonder if it has any atmosphere at all. An atmosphere with water-based clouds like Earth’s would have been blown away by solar radiation long ago. But they believe its clouds are metallic, a combination of titanium and silicates — the materials that make up most of Earth’s crust.
“We think that the clouds will condense into droplets and that titanium will rain down in some parts of the atmosphere,” Jenkins said.
Researchers used the European Space Agency’s CHEEOPS orbiting telescope to study the planet.
“No planet like this has been discovered to date,” said Sergio Hoyer, an astronomer at the Astrophysics Laboratory in Marseille, France and lead author of the study.
According to study co-author Vivian Parmentier, an astronomer at France’s Côte d’Azur Observatory, an atmosphere orbiting so close to its star makes it “a planet that shouldn’t exist.”
“The super-reflective cloud cover may help prevent the planet from heating up too much and being stripped of its atmosphere,” Parmentier said. “It’s quite unique because all the other planets at this temperature are hot enough to maintain their atmospheres, which are too hot to form clouds and dark like charcoal.”
It appears to be tidally locked to its star, just as the Moon is toward Earth, with a permanent day side facing the star and a permanent night side facing away.
All previously known planets orbiting their stars in less than one Earth day were either “hot Jupiters,” gas giants similar to our Solar System’s largest planet but much hotter due to solar radiation — or rocky planets smaller than Earth and lacking an atmosphere. .
Classified as an “ultra-hot Neptune,” researchers wonder whether LTT9779b started as a gas giant only to lose much of its atmosphere, or whether it started at its current size.
More than 5,000 planets beyond our solar system – called exoplanets – have been discovered, many of which are very different from the eight planets in our solar system. As increasingly capable instruments come on line — the James Webb Space Telescope became operational last year, and a much larger telescope is under construction in Chile — more discoveries await.
“The diversity of exoplanets is amazing,” Parmentier said, “and we’ve only scratched the surface.”