A window on exoplanet skies can be seen from the JWST

Observation of WASP-39b with the Joint Wilkinson Microwave Anisotropy Probe on an Exoplanet

“This shows that, when it comes to delving into exoplanetary atmospheres, JWST is every bit as powerful as we hoped,” says Hugh Osborn, an exoplanet scientist at the University of Bern in Switzerland.

“We’ve studied lots of planets before,” says Laura Kreidberg, director of the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, and part of the observation team. We have never seen a data set like this before. The team posted five papers1,2,3,4,5 on its findings on the arXiv preprint server on 22 November.

In July, the telescope saw the planet for more than 40 hours. Initial results showed carbon dioxide in the planet’s atmosphere. It was the first time that the gas had been seen on an exoplanet.

“These spectra are just exquisite in their detail, and reveal an additional way that the star affects the planet’s atmospheric composition, through photochemistry,” says Victoria Meadows, an astronomer at the University of Washington in Seattle.

To explain their proximity, hot Jupiters are expected to migrate inward. It is not clear whether this is a slow process, over many millions of years, or whether it comes from a star or another planet. Knowing WASP-39b’s composition might help the astronomer determine which scenario occurred.

The planet is locked to its star, with the same face pointing at it, because of the immense attraction between them. Astronomers have seen incomplete cloud cover before, but this is the first time that they have seen it on an exoplanet. The planet is only about 40% covered by clouds at the boundary of night and day.

TRAPPIST-1b: a new planet with a dense atmosphere? A comment on first results from the JWST experiment at the University of Montreal

“We’re in business,” Björn Benneke, an astronomer at the University of Montreal, said during a symposium on first results from JWST in Baltimore, Maryland, on 13 December.

The intial planet in the system, TRAPPIST-1b, was shown in a poster presentation by the University of Montreal. She, too, has not been able to tease out a signal indicating the planet’s atmosphere just yet. Preliminary studies show it probably doesn’t have a hydrogen-rich atmosphere like planet 1g.

Previous studies with the Hubble and Spitzer space telescopes, using a different technique, showed that TRAPPIST-1b — the innermost planet in the system — probably doesn’t have a large puffy atmosphere made mostly of hydrogen2. But researchers couldn’t rule out whether it has a dense atmosphere, as Earth might have had billions of years ago.

The astronomer who was not involved in the work says that they needed the first look to know what they were dealing with. Benneke declined to speak with reporters about the TRAPPIST-1g results, citing a paper under review at a scientific journal.

Observations of Terrestrial Planets. II. First Results from the Near-Infrared Imaging and Spectroscopic Survey (JWST)

There is a lot of work to be done to understand the limits of this habitability. The finding will help understand how photochemistry protects exoplanetary surfaces from high-energy irradiation. It also tightens constraints on the parameters used in models of planetary formation. Both advances pave the way to future observations of planets that are similar to Earth.

The wavelength ranges of the three instruments used in the studies are all in the near infrared, the range in which one expects to find spectral features of the key atmospheric molecules reported. But each instrument has different configurations that enable access to different wavelength ranges and spectral resolving powers. Rustamkulov et al. Feinstein and Ahrer used two different configurations of an instrument. The Near-Infrared Camera was used by Ahrer and his team. Between them, the teams observed light with wavelengths spanning 0.5 to 5.5 micrometres (Fig. 1).

Various data-processing algorithms were used for each instrument to traverse the complex path from raw data to the final spectrum. And although these efforts returned mostly similar results, the diverse approaches show that there is no consensus yet on the optimal way to process JWST data — indeed, there is much still to learn. Some problems have already begun to be addressed in these initial studies, including how best to manage pixels that are saturated1 (giving unreliable signals), and what to do when mirror segments spontaneously tilt during observation2.

The radiation from TRAPPIST-1 in the mid-Infrared wavelength was 20 times more red than what a human eye can see, and it changed when TRAPPIST-1b moved behind the star. By measuring the brightness of the star and planet together compared with that of the star alone, astronomers could calculate how much came from the planet.