New research from a University of Washington-led team of astronomers has offered new insight on climate models for the seven planets that orbit one of the most interesting stars in the universe TRAPPIST-1.
TRAPPIST-1 is located 39.6 light-years from the sun, in the constellation Aquarius. The solar system is home to an ultra-cool red dwarf star that is slightly larger, but much more massive, than the planet Jupiter. The star is orbited by seven rocky planets. Three of those planets are considered to be within its habitable zone of the star.
The new paper (which focuses on climate) could help astronomers study more effectively planets around stars, unlike our sun.
“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,” said Andrew Lincowski, UW doctoral student and lead author of a paper published Nov. 1 in Astrophysical Journal.
“We conducted this research to show what these different types of atmospheres could look like.”
So, what did they find?
The team discovered, briefly put, that due to an extremely hot, bright early stellar phase, all seven of the star’s worlds may have evolved similarly to Venus, where any early oceans they may have developed on the surface most likely evaporated leaving dense, uninhabitable atmospheres.
However, one planet, TRAPPIST-1 e, could be an exception, say astronomers.
According to the new study, TRAPPIST-1 e could be home to an Earth-like ocean, as previous studies have also indicated.
“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,” said Lincowski. “It’s just a gold mine.”
Previous papers have modeled TRAPPIST-1 worlds, Lincowski said, but he and this research team “tried to do the most rigorous physical modeling that we could in terms of radiation and chemistry — trying to get the physics and chemistry as right as possible.”
The team’s radiation and chemistry models allowed them to develop spectral, or wavelength, signatures for each possible atmospheric gas, which helps astronomers to better predict where to look for such gases in exoplanet atmospheres.
Lincowski said when traces of gases are actually detected by the Webb telescope, or others, some day, “astronomers will use the observed bumps and wiggles in the spectra to infer which gases are present — and compare that to work like ours to say something about the planet’s composition, environment and perhaps its evolutionary history.”
Their new climate model indicates that:
- TRAPPIST-1 b, the closest to the star, is a blazing world too hot even for clouds of sulfuric acid, as on Venus, to form.
- Planets c and d receive slightly more energy from their star than Venus and Earth do from the sun and could be Venus-like, with a dense, uninhabitable atmosphere.
- TRAPPIST-1 e is the most likely of the seven to host liquid water on a temperate surface and would be an excellent choice for further study with habitability in mind.
- The outer planets f, g, and h could be Venus-like or could be frozen, depending on how much water formed on the planet during its evolution.
“This may be possible if these planets had more water initially than Earth, Venus or Mars,” he said. “If planet TRAPPIST-1 e did not lose all of its water during this phase, today it could be a water world, completely covered by a global ocean. In this case, it could have a climate similar to Earth.”