This could be the closest we’ve come to finding a planet that could support life: astronomers have detected an atmosphere around a rocky Earth-like planet orbiting in the habitable zone around its star, a monumental first.
The rocky planet, called LHS 1140 b, is located 48 light years from Earth and, according to this new research, has an atmosphere that contains helium. It is also the first rocky planet whose atmosphere can be directly detected. This is the first rocky planet found with an atmosphere that is also found in the living areameaning it is at the right distance from its star for liquid water to potentially exist on the planet. As we continue to search the cosmos for planets that could be considered “habitable,” this planet ticks more boxes than almost anything we’ve ever seen.
“We’ve actually directly detected helium present in the atmosphere itself, and that’s the first direct detection of any rocky exoplanet, which is really exciting… and then there’s the added bonus that it’s in the habitable zone, which is super exciting for astrobiology and habitability and the search for life,” said lead author Collin Cherubim, who recently earned his Ph.D. from Harvard University, told Space.com. “It feels a little surreal.”
What is this planet like?
Let’s explore this planet and the system where it “lives”.
This exoplanetor planet outside our solar system, was first discovered in 2017 by a team led by astronomer Jason Dittmann, who is now a co-author of this new discovery.
“This planet was found about 10 years ago, and now we say, okay, that’s an atmosphere,” Dittman told Space.com. “We’re slowly narrowing the gap and checking these boxes…we’re finding a planet that’s rocky, a planet that’s the right temperature, and now…okay, we finally found one that has an atmosphere.”
And being a rocky planet, “there’s definitely a surface…it’s made of rocks,” Dittman said. What is the surface of the planet like? We can’t say yet, but researchers who found this planet’s atmosphere believe there’s a good chance it has water.
While orbiting a red dwarf starwhich is smaller and cooler than the Sun, orbits closer to our star than we do, maintaining a temperature that keeps the planet in the “Goldilocks zone,” where liquid water could exist on its surface.
“It probably has a lot of water too,” Cherubim said. “If you have a certain amount of atmosphere that can produce a little bit of a greenhouse effect, which we know is happening now… it will most likely be what we consider habitable conditions on Earth, and conditions that would likely support liquid water.”
So does it look like Earth? While certainly not a copy of Earth, this planet can be considered similar to Earth in two main ways, Cherubim shared. One: its general composition. The planet is rocky, probably with an iron core, and (we now know) has an atmosphere. And two: the temperature of the planet is adequate for liquid water, which is necessary for life, at least as far as we understand it on our planet.
Find an atmosphere
The discovery of the first exoplanet was confirmed just over 30 years ago. Since then, scientists have found more than 6,000 exoplanets and counting. And although some rocky planets have been found in the habitable zone of their star, it has not been until now that an atmosphere around a rocky planet in the habitable zone has been confirmed.
One of the reasons scientists have had a hard time finding planets with atmospheres is their stars. LHS 1140 b orbits the most common type of star, a red dwarf, which is about a third the size of our sun. This type of star remains active much longer than stars like our sun. This activity means it releases bursts of extreme radiation such as solar flares and coronal mass ejections. And the extreme radiation around these stars typically strips away the atmospheres of the planets orbiting them, so astronomers have wondered whether the planets orbiting these stars might have any atmosphere at all.
“This discovery is very important because it shows that at least this rocky planet has preserved an atmosphere for billions of years,” Cherubim said. It’s “an authentic, solid way of saying yes, atmospheres can survive on rocky exoplanets.”
There may be other gases besides helium in the planet’s atmosphere, and some of its atmosphere may have been previously removed by radiation from its star. But the red giant orbiting this planet is about 6 billion years old, a few billion years older than the age at which its extreme radiation activity begins to calm down. So while some helium still slowly escapes from the planet’s atmosphere over time, the team hopes the planet will retain an atmosphere, Dittman shared. After all, even the Earth’s helium is slowly leaking out. our own atmosphere.
The proof is in the atmosphere.
To prove that this planet has an atmosphere, the team started with a prediction Cherubim made during graduate school. It all started with a theoretical model and the sneaking suspicion that there must be rocky exoplanets with atmospheres different from Earth’s.
“This came from a very specific prediction of a planetary evolution model that I developed myself, from scratch, from first principles, for my PhD as a theorist, and I made a very specific prediction about this planet,” Cherubim said. “And then I went out and did something quite unexpected and strange using this technique that’s normally reserved for observing giant planets, and I used it for a rocky planet, something that no one had done before.
“Lo and behold, I made this measurement that was actually consistent with my prediction. And it was really nice to bring the scientific method full circle.”
The team took the theoretical model that Cherubim developed in graduate school and put it to the test using the Echelle Warm Infrared Spectrograph (WINERED) at the Magallanes Observatory in Chile. And with their observations, they were able to see LHS 1140 b and a other planet transit or pass in front of its star on the same night. Using this spectrographic data, they were able to identify the signatures of the molecules in the atmospheres of these planets as they passed in front of the star. And although one planet did not return results, this planet showed a direct and undeniable helium signature.
Are there aliens?
When you look at a planet that is rocky, has an atmosphere, and is in the habitable zone (meaning it could have liquid water), the question of life arises quite quickly.
But researchers don’t have enough data to reach that conclusion. “I am not claiming that this planet has life,” Cherubim made clear. With more research, scientists could better understand what else could be in this planet’s atmosphere and could confirm if it has water. More observations may not be able to confirm habitability or identify life on the planet, but they could at least help us better understand planets like this one.
Since this is the first such planet discovered, further exploration will help us put the pieces together. But it is certainly a big step forward in the eternal human quest to answer the question: are we alone?
This work was described in a study published in the journal Science.
