exoplanet TRAPPIST-1b has no atmosphere after all

NASA, ESA, CSA, J. Olmsted (STScI)Impression of the exoplanet TRAPPIST-1b and its star

NOS Nieuws•vandaag, 14:37

An exoplanet 40 light-years away that was thought to be very similar to Earth has been found to have no atmosphere at all. That is the latest cosmic revelation from the James Webb space telescope, which aimed its mirror at the star TRAPPIST-1.

No less than seven planets were discovered about six years ago near the star named after the TRAPPIST telescope, a project of Belgian origin. Possibly with oceans full of water, astronomers exulted in February 2017. On some, who knows, life could have arisen as a result.

On the nearest planet 1b that is not so likely, it now appears. The planet always has the same side facing its sun and on that side it is about 230 degrees, so there is no atmosphere.

That was not what some astronomers had expected. Planet TRAPPIST-1b is much closer to its star than Earth, but that star is much fainter than our sun. Some astronomers actually expected a very thick atmosphere, such as on Venus.

NatureImpression of the 7 exoplanets around TRAPPIST-1 from 2017

At the time, astronomer Lucas Ellerbroek was very enthusiastic about the discovery of the TRAPPIST planetary system, almost a mini-copy of our own solar system. He is not disappointed by the latest discovery of the James Webb. “It’s not super surprising. The planet is slightly heavier than Earth, so it should be able to hold an atmosphere. But in our solar system you also see big differences, for example between Venus and Earth. And for a planet so close to an active star, I am not surprised if the radiation from that star would affect the atmosphere.”

He emphasizes that there are six exoplanets left around the star and that TRAPPIST-1d, -1e, -1f and -1g are bigger contenders in the search for habitable planets. “So I’m not pessimistic, it’s still possible.”

The discovery is primarily a new triumph for the James Webb and the MIRI, an instrument on the telescope that was partly developed in the Netherlands. It has never been possible to study the thermal radiation of a rocky planet as small as TRAPPIST-1b. Insofar as that happened at all, these were large Jupiter-like exoplanets. Ellerbroek: “One of the promises of the James Webb was that it could investigate the atmosphere of these types of planets. That promise has now been fulfilled.”

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