Astronomers have discovered the first atmosphere of a planet in the habitable zone of another star

The search for life beyond Earth has borne little fruit. That remains true, but scientists have new hope. For the first time, astronomers have discovered an atmosphere surrounding an exoplanet in the habitable zone of its host star.

Say hello to LHS 1140b, a rocky Earth-like planet that lives about 48 light-years away. For reference, Voyager 1 is quickly approaching its first day of light after nearly 50 years of flight. LHS 1140b is in the “Goldilocks” zone for its star, meaning it is far enough away that it won’t be fried like Mercury, but close enough that it will become hot enough to support liquid water.

According to a new study published in Science, the “special” part of this discovery isn’t just the habitable zone around a star. This is because it seems to meet additional criteria that interest scientists: that is, it is rocky, not a gas giant, and it can still retain an atmosphere despite difficult conditions. An atmosphere is what helps stabilize surface temperatures, which is essential for life to exist.

“This is very exciting,” Collin Cherubim, lead author of the study and a Harvard PhD, said in an email. “A major goal in this field has been to understand whether rocky exoplanets can retain atmospheres.”

Cherubim says that most rocky planets orbit M-class dwarf stars, which “emit high-energy radiation for much longer than stars like the sun.” Most rocky planets are stripped of their atmospheres fairly early in their life cycles, thanks to this radiation, the stripping effect of the solar wind and other factors, eliminating their chance to host life.

Until LHS 1140b, Earth was the only rocky planet humans had ever observed with an intact atmosphere.

It wasn’t easy to find. Chérubins used a computer model that he had developed during his work and which “simulates the evolution of the atmospheres of exoplanets over billions of years”. These models predicted the existence of “helium worlds,” or rocky planets with helium (or at least mostly helium) atmospheres. Cherubs tested his theory with LHS 1140b and struck the proverbial gold.

Is there life on LHS 1140b?

Whether or not LHS 1140b contains life is a complicated question. Cherubim says science recognizes three main requirements for a planet to support life: an atmosphere, adequate temperatures to keep water liquid, and a mostly rocky planet to make it hospitable. LHS 1140b seems to have it all.

The main problem is that the upper atmosphere of LHS 1140b is almost entirely helium, which is also “hydrogen depleted”. This does not bode well for life, as helium generally cannot support life as we know it here on Earth.

The Cherubim say the planet is also tidally locked to its star, like the Moon on Earth, meaning one side of the planet has permanent day and the other side has permanent night. It’s also about 70% larger than Earth, meaning gravity is almost twice as strong. These findings don’t rule out life entirely, but if LHS 1140b harbored life, it would surely be very different from life on Earth.

Cherubim also admits that researchers don’t yet know whether the planet has a rocky surface or whether it’s entirely covered by an ocean, the latter case being important for the search for life. Computer models developed by Cherubs predict that the lower atmosphere could even contain gases more conducive to life, such as carbon dioxide, water and even oxygen.

“Although we need more data to see what’s happening in the rest of the atmosphere, this may be the first known helium world,” Cherubim said. “The fact that these rocky worlds can retain helium atmospheres is not only good for habitability prospects, but it also tells us our [computer prediction] models achieve something.”

Until then, Mars is the most likely candidate for detecting signs of life, since researchers have already identified possible biosignatures in its soil.

Another potential candidate for habitability is K2-18b, where scientists have reported tentative evidence of the presence of dimethyl sulfide, a compound commonly produced by ocean phytoplankton. Scientists are also interested in the Trappist-1 star system, which has seven Earth-sized planets, including three in the star’s habitable zone.

Joe is a freelance journalist. It all started with a lifelong passion for building his own PCs, which he first did as a teenager. It has become a permanent pleasure to put words on the subject on the Internet. He has written for CNET, PCMag, Mashable and SlashGear as a freelance writer and worked as a senior editor at Android Authority for 10 years. When he’s not writing about tech and science, he’s learning the ins and outs of home repair, gaming, bass, and posting PC building help and gaming subreddits. He firmly believes that orange juice should contain pulp. See full bio