Meet Janssen, a world 41 light years away that might have an atmosphere

This artist’s concept shows what the exoplanet 55 Cancri e could look like. Also called Janssen, 55 years old … (+) Cancri e is the so-called super-Earth, a rocky planet significantly larger than Earth but smaller than Neptune, which orbits its star at a distance of only 1.4 million miles (0.015 astronomical units) , completing a complete orbit in less than 18 hours. .

NASA, ESA, ASC, Ralf Crawford (STScI)

Scientists using the James Webb Space Telescope may have detected an atmosphere around an exoplanet – a planet that orbits a star other than ours – relatively close to the solar system.

Located just 41 light years away in the constellation Cancer, Janssen (also called 55 Cancri e) is currently the best evidence yet of an atmosphere around a terrestrial, rocky planet outside the solar system.

However, this is not an “Earth 2.0”, as Janssen is a hot and hellish world.

“Super-Earth”

Janssen, one of five known planets orbiting a sun-like star, has a diameter nearly twice that of Earth. It’s also slightly denser. This places it in the category of “super-Earths” or “sub-Neptune”.

Published this week in Nature, a new paper contains observations that show the exoplanet can maintain a gaseous atmosphere. And this, even if it is a world of very hot lava with probably a sea of liquid magma.

Unlike anything else we have in our solar system, Janssen orbits its star in just 18 hours and therefore receives intense radiation. “The planet is so hot that some of the molten rock is expected to evaporate,” said team leader Renyu Hu of NASA’s Jet Propulsion Laboratory (JPL).

This light curve shows the change in brightness of the 55 Cancri system as a rocky planet 55 … (+) Cancri e, the closest of the five known planets in the system, is moving behind the star.

Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI) Science: Aaron Bello-Arufe (NASA-JPL)

Night and day

The team used JWST’s near-infrared camera and mid-infrared instrument to simultaneously measure infrared light coming from Janssen’s day and night sides. Analysis of the light showed that the planet could be surrounded by an atmosphere of carbon monoxide or carbon dioxide. It is likely that bubbles are coming from the planet’s interior.

If these results are proven, they greatly expand the scope of which planets might contain an atmosphere, although no one expects to find signs of life on a world as hot as Janssen.

Enigmatic exoplanet

“Despite enormous amounts of observation time obtained with a dozen ground- and space-based facilities over the past decade, its very nature has remained elusive until today,” said the Center’s Brice-Olivier Demory. for space and habitability CSH of the University of Bern and member of the NCCR PlanetS and co-author of the study. He called it “one of the most enigmatic exoplanets.”

It is hoped that Janssen can provide information on early Earth, Venus and Mars, all of which are believed to have been covered in lava oceans in the past. “Ultimately, we want to understand what conditions allow a rocky planet to maintain a gas-rich atmosphere: the key ingredient for a habitable planet,” Hu said.

I wish you clear skies and wide eyes.