This story has it all: a fascinating exoplanet, the potential for future studies, and my favorite topic, the puzzle of planetary formation.

Let’s start with the exoplanet. It’s a very hot super-Earth called Gliese 486b, located about 26 light-years away – pretty close in astronomical terms. The surface temperature is around 430 degrees Celsius, so there are exactly zero expectations of finding life there. It’s 30 percent bigger than Earth and about three times heavier. Think Venus when you think of this world. There could even be scattered lava rivers running over the surface. Not exactly the picture of habitability we usually search for.

And yet, this planet was announced with no less than four press releases yesterday. So what has all the scientists excited? This super-Earth still has its atmosphere, and it’s a transiting planet, so we can study that atmosphere in the near future. We haven’t been able to study any other super-Earth this way. The findings were published in Science, and co-author Dr. Ben Montet notes: Understanding super-Earths is challenging because we don’t have any examples in our backyard. Gliese 486b is the type of planet we’ll be studying for the next 20 years.

That study begins with learning more about Gliese 486b’s atmosphere using spectrographs. Since this exoplanet transits in such a way that we can detect the changes in brightness of the host star, we can then use that geometry to do spectroscopy in two ways. The first method is used when the planet passes directly in front of the star. The light from the star then passes through the atmosphere of the planet, and we can use transmission spectroscopy to determine the composition of the atmosphere.

The second method is used when the planet begins to make that pass back around the back of the star from us. At that point, the light of the star illuminates the surface of the planet, and we can now use emission spectroscopy to confirm the composition of the atmosphere and possibly catch any components we might have missed.

Once again, this is not a planet for us to live on. Visit, maybe, with good space suits to protect us from the heat and keep us breathing. The gravity is much stronger than on Earth, and the planet is so close to its star that stellar flares and storms would be a problem. It would be nice to visit from a distance, but right now, I’d settle for just understanding the atmosphere from our comfy planet right here.

More Information

IAC press release

MPIA press release

NOIRLab press release

UNSW press release

“A nearby transiting rocky exoplanet that is suitable for atmospheric investigation,” T. Trifonov et al., 2021 March 5, Science