“There are some terrestrial-type atmospheres that we can rule out,” Lustig-Yaeger said. “The planet cannot have a thick methane-dominated atmosphere similar to that of Saturn’s moon Titan.”
The team also notes that while it’s possible the planet has no atmosphere, there are some atmospheric compositions that can’t be ruled out, such as an atmosphere made entirely of carbon dioxide (CO2). “Although counterintuitive, an atmosphere of 100 percent carbon dioxide is so much more dense that it becomes very difficult to detect,” said Lustig-Yaeger.
So the team needs even more precise measurements to distinguish between an atmosphere consisting entirely of carbon dioxide and no atmosphere at all. It is planned that the researchers will be able to make more observations this summer, so that they will obtain additional spectra.
The Webb telescope also revealed that the planet is several hundred degrees warmer than Earth. That means if clouds are detected, the researchers could conclude that the planet is more like Venus. That planet has a carbon dioxide atmosphere and is constantly shrouded in thick clouds.
“We are at the forefront of the study of small, rocky planets,” said Lustig-Yaeger. “We’re just seeing the tip of the iceberg of what their atmospheres could be.”
The researchers also confirmed that the planet is close to its star and completes a full orbit in just two days, information revealed almost instantaneously by Webb’s precise light curve. Although LHS 475 b is closer to its star than any planet in our solar system, the red dwarf it orbits is only half as hot as our sun. This means that the researchers assume that the planet could still have an atmosphere.
