What the James Webb Telescope tells us about this potentially habitable exoplanet

TRAPPIST-1 is Dwarf starDwarf star Red – understand that he is cooler than us sunsun And barely bigger than JupiterJupiter – Located around 40 Light yearLight year in Earth. It attracts a lot of attention because it is surrounded by no less than seven planets. Subordinate ExoplanetsExoplanets Floor size. It is enough to hope to find habitable worlds. If he doesn’t… he lives!

the Astronomy scientistsAstronomy scientists They were eagerly waiting for the James Webb Space Telescope (JWST) to tell them more about these planets. Especially on the one closest to Trappist-1. Scientists call them Trappist-1b and Trappist-1c. And by measuring them emissionemission In infrared light, it should be possible to see if these exoplanets contain A AtmosphereAtmosphere.

Atmosphere of Trappist-1b: Beware of ‘ghost signals’

The first results published by astronomers in recent weeks described them as exoplanets that may be devoid of atmosphere. Today, researchers from the University of Montreal (Canada) report in the journal Astrophysical Journal Letters, Some details regarding Trappist-1b in particular. Thanks to spectroscopic observations made as the planet passes in front of its star. When light from a star passes through the atmosphere of one of its planets, it is imbued with a unique signature. That of AtomsAtoms And the MoleculesMolecules that make up this atmosphere.

It is precisely on this point that the work of researchers at the University of Montreal is important. They showed that the activity of a star like Trappist-1 — red dwarfs with many spots and shaking with numerous, violent outbursts — could generate types of… “ghost signals”. Observations that misleadingly indicate the detection of a particular molecule in the atmosphere of an exoplanet. “We need to take this into account to interpret the data returned by a file James Webb Space TelescopeJames Webb Space Telescope »confirms Olivia Lim, lead author of the study, in A Press release from the University of Montreal.

Trappist-1b does not have a dense atmosphere

So the researchers incorporated a factor into their data that they call… “Radioactive contaminationRadioactive contamination Astral ». Enough to allow them to exclude certain types of Trappist-1b’s atmosphere. With a high level of confidence, they argue that the atmosphere is without it cloudscloudsAnd rich hydrogenhydrogen For example, it does not match their data. The researchers thus confirm the results (see article below) published last March: There does not appear to be a clear, widespread atmosphere around Trappist-1b. They also show how good the instrument is NerisNerisHe is efficient and sensitive when focusing on studying planetary atmospheres.

So there is no significant atmosphere for Trappist-1b. But why isn’t the weather nicer? A bit like that surrounding a satellite SaturnSaturn, TitanTitan Single moonmoon Our solar system would have its own atmosphere. An atmosphere composed of water (H₂Oof Carbon DioxideCarbon Dioxide (Co₂) and methane (CH₄). Data from the James Webb Space Telescope cannot rule this out yet. More observations will still be needed to find out.

Is exoplanet Trappist-1b a habitable Earth 2.0? The James Webb Telescope has the answer

It belongs to one of Star systemsStar systems The most promising for the search for extraterrestrial life: the exoplanet Trappist-1b was explored by the instrument MerryMerry Using the James Webb Telescope, searching for the atmosphere. What does this aggregated data tell us?

Article by Leah Forneson published on 03/28/2023

Located 40.5 light-years from Earth, the star TRAPPIST-1 has intrigued astronomers since its discovery in 1999. In fact, this red dwarf star is home to at least seven exoplanets, all of which have near-Earth characteristics. Rocky planetsRocky planets from U.S Solar systemSolar system: measuring, MassMassOr even density! Among them, three are in the habitable zone, which is the area that allows water in the state liquidliquid .

That’s why one of the first missions of the James Webb Telescope was to focus on it, and point the MIRI instrument at this interesting planetary system. So he pointed the camera lens at Trappist-1b, the exoplanet closest to the star. The results have just been published in nature. “These observations really take advantage of Webb’s ability to use mid-infrared light.”Thomas Green details in A ESA press release, AstrophysicistAstrophysicist At the Ames Research Center of NASANASA And the lead author of the study. “No previous telescope had the sensitivity to measure such faint mid-infrared light.”

Trappist-1b has no significant atmosphere

With a diameter similar to that of Earth, Trappist-1b lies much closer to its star, with the distance to its star being 10 times less than the distance between them. MercuryMercuryAnd the sun. But because of its star, a red dwarf whose radiance is much lower than that of the Sun, a yellow dwarf, the light it receives is very similar, equivalent to 4 times that of Earth. above all, “This planet has been locked down before TidesTidesWith one side always facing the star and the other in perpetual darkness“, explains Pierre-Olivier Laguege from CEA, co-author of the article. If there is a climate for circulation and redistribution heatheat The day side will be cooler than if there was no atmosphere.

This is exactly what scientists were looking for: using a technique called…eclipseeclipse Secondly, they were able to measure change in brightnessbrightnessFor the system when the planet passes behind the star. Then we can return to the planet’s brightness by subtracting the measurement during an eclipse from the measurement during which an eclipse does not occur. All in infrared thanks to James Webb’s Merry Tool, which is compatible with Thermal raysThermal rays . This brightness can then be linked to the temperature of the planet, and thus to the presence or absence of an atmosphere!

The results are somewhat disappointing: nothing! “We compared the results to computer models that show the temperature in different scenarios“, explains Elsa Ducrot, a scientist at CEA and co-author of the study. The results are almost completely consistent with A Black bodyBlack body Made of bare rock and no atmosphere to distribute heat. We also didn’t see any signs of thatAbsorptionAbsorption of light by carbon dioxide, which will be evident in these measurements.

“It’s a really important step in the history of exoplanet discovery.”

If this result is not positive, it confirms the capabilities of James Webb, and remains very encouraging for the future. Because, for the first time, a temperate exoplanet has been diagnosed. “There was a goal that I dreamed of achievingP. Lagage adds. This was one. This is the first time we can detect emission from a temperate, rocky planet. This is a truly important milestone in the history of exoplanet discovery.

After that, other planets in the TRAPPIST-1 system, or even other planetary systems, will be explored in the same way. Especially around red dwarfs, which are the stars most likely to detect extraterrestrial life. “There are ten times as many stars as these milky waymilky way That there are stars like the Sun, and that they are twice as likely to have rocky planets as there are stars like the SunTB Green concludes. But they are also very active – they are very bright when young and emit emissions MissilesMissiles Al-Mounir and X rayX rayWhich can destroy the atmosphere.