Red dwarf TRAPPIST-1 is located less than 40 light-years away and is orbited by seven Earth-sized planets. Three of these are in the habitable zone of their stars, with the possibility of liquid water flowing on their surface. Astronomers are so interested in this system that we know more about it than any other system besides our own. Now, a new model has just given us more of an insight into what the planets’ climateS might be like.
The study, published in The Astrophysical Journal, focused on modeling realistic climate scenarios based on the possible chemical composition of the primordial atmosphere of the planets and the radiation the star emits. Red dwarfs are much cooler and smaller stars than our Sun, but more active. Since the planets orbit very close to it (closer than Mercury orbits the Sun), the effect is unlike anything we have experienced in the Solar System.
The seven planets are labeled b to h based on their distance from the star. TRAPPIST-1 b is believed to be too hot to even have clouds. Planets c and d get more starlight than Venus so the team believes that they might be Venus-like with thick, dense, toxic atmospheres.
This leads to TRAPPIST-1 e, which is the first planet in the habitable zone and, according to the researchers, the most likely one to have liquid water. It might even be an ocean world if it started off water-rich and then kept it over its evolution. The other three could either be Venus-like worlds with a runaway greenhouse effect or icy worlds.
“We are modeling unfamiliar atmospheres, not just assuming that the things we see in the Solar System will look the same way around another star,” lead author Andrew Lincowski, a graduate researcher from the University of Washington, said in a statement.
“We conducted this research to show what these different types of atmospheres could look like. This is a whole sequence of planets that can give us insight into the evolution of planets, in particular around a star that’s very different from ours, with different light coming off of it. It’s just a gold mine.”
While there is a certain interest in if and how many of the TRAPPIST-1 planets are habitable, the paper focuses on climate and what potential signatures may be spotted in the atmosphere of these exoplanets. Given the dimness of the star, it is likely that a signature of gases such as carbon dioxide will be more pronounced.
The team has an eye on the near future to further their studies. Astronomers expect the James Webb Space Telescope, which will launch in 2021, to be able to directly observe these planets’ atmospheres. This work gives an idea of what we might see there.