Around 40 light-years from Earth, seven rocky worlds orbit a cool, red star named Trappist-1. Some of these planets may be habitable to life as we know it, which has led astronomers to point the James Webb Space Telescope at each member of the septuplet. To date, they have been left disappointed: several of the planets appear to be bare rocks exposed to the horrific void of space.
But after thorough analysis of one of these worlds, Trappist-1e, astronomers have not been able to rule out the presence of a nitrogen-gas-rich atmosphere around it.
In our solar system, Saturn’s moon Titan has an atmosphere dominated by nitrogen gas. So does Earth. And, like Earth, Trappist-1e is at just the right distance from its star for things to be warm and clement.
“If there’s one of these planets that could potentially sustain liquid water on the surface, it’s probably that one,” said Nikole Lewis, an exoplanet researcher at Cornell University and an author of two papers published Monday in Astrophysical Journal Letters.
To be clear, the Webb telescope did not detect an atmosphere, and scientists have no idea what the surface of Trappist-1e is like. But based on the data they have, an atmosphere “is still within the realm of possibility,” said Néstor Espinoza, an astrophysicist at the Space Telescope Science Institute in Baltimore and an author of both papers.
Ever since their discovery was announced in 2017, the seven Trappist-1 worlds have beguiled astronomers. They all seem rocky. Could any of them be like our own pale blue dot?
The star itself, Trappist-1, is not like our sun. That’s both good and bad news for those seeking a world where things may be able to live. The seven planets orbit remarkably close to the star. But as the star is a dim, small and cool red dwarf, its habitable zone — the band within which a planet is able to have liquid water — hews close to the star.
However, the star is also hyperactive and hostile, often erupting lethal flares that might strip away planetary atmospheres.
When astronomers took a close look at the system’s innermost planets, Trappist-1b and 1c, they found no signs of atmospheres. Last month, other researchers revealed that Trappist-1d does not have any molecules common to Earth’s atmosphere, like water, methane or carbon dioxide.
Next was Trappist-1e. In 2023, scientists aimed the Webb telescope at the planet. If it had an atmosphere, any starlight slipping through it and reaching the telescope would contain subtle signatures of its gassy molecules.
Unraveling the data took considerable effort. “It’s a really alien world orbiting a star that’s very different from the Sun,” Dr. Espinoza said.
It also doesn’t help that “the star is a giant pain,” Dr. Lewis said. Being so furious and nearby, its stellar atmosphere contaminates Trappist-1e’s own space environment. But, having disentangled as much of that contamination as possible, Dr. Lewis’s team has managed to rule out several possibilities.
The planet does not appear to have a hydrogen-gas-dominated atmosphere. Its skies are also seemingly not rich in carbon dioxide, meaning it’s not like Mars (a frigid desert with a light CO2 shell) or Venus (a scorched, acrid wasteland suffocating in CO2).
The pattern of starlight received by the Webb telescope has bumps and wiggles, which could be hints of nitrogen. But the team has managed to observe Trappist-1e only a handful of times so far, and residual stellar contamination may be an issue. For now, they did not find strong evidence for an atmosphere. But neither could they say with any conclusiveness that it lacks a nitrogen-rich atmosphere.
Surveys of Trappist-1e using the Webb telescope are ongoing. Eventually, scientists will know what type of atmosphere surrounds the planet, if it has one at all.
Red dwarf stars like Trappist-1 are commonplace in the cosmos, so knowing if their rocky planets can hold onto an atmosphere — and potentially be habitable — is of paramount importance, said Jessie Christiansen, the chief scientist of the NASA Exoplanet Science Institute who was not involved with either paper.
Until now, the Trappist-1 system seemed bereft of any protective atmospheres. And if none is detected on Trappist-1e, “that might suggest that cool stars like Trappist-1 are not the best environments for life,” said Heidi Hammel, an astronomer at the Association of Universities for Research in Astronomy who was not involved with either paper.
But for now, there’s a chance that Trappist-1e does have an atmospheric shield to defend itself against its angry star. “There is a glimmer of hope,” Dr. Christiansen said. “It’s very exciting.”
The post Hopeful Hint of an Earthlike Atmosphere on a Distant Planet appeared first on New York Times.
