Our best look yet at an Earth-Sized Exoplanet Comes from JWST TRAPPIST-1b

 

Artist's impression of TRAPPIST-1b. (NASA, ESA, CSA, J. Olmsted/STScI, T. P. Greene/NASA Ames, T. Bell/BAERI, E. Ducrot & P. Lagage/CEA)

It is unlikely that an exoplanet the size of Earth in the possibly most hopeful extraterrestrial system for the presence of life could support modern life.

 

New observations from the James Webb Space Telescope show that the innermost world of the TRAPPIST-1 system, an exoplanet known as TRAPPIST-1b, reaches a scorching 230 degrees Celsius (446 degrees Fahrenheit) and is unlikely to have an atmosphere wrapped around its rocky body. TRAPPIST-1b is 1.4 times the mass and 1.1 times the radius of Earth.

This is not a surprise because TRAPPIST-1b rotates around its host star in just 1.5 days and receives four times as much stellar radiation as Earth does; however, this is the first time we have been able to make these measurements for a world this small and cool—the closest to Earth yet.

 

Naturally, the knowledge will also aid researchers in learning more about the other six exoplanets known to revolve around the red dwarf star TRAPPIST-1, whose potential for habitability is unclear.

The French Alternative Energies and Atomic Energy Commission (CEA) astronomer Elsa Ducrot says that it is simpler to characterise terrestrial planets around smaller, cooler stars.

 

"The TRAPPIST-1 system is a fantastic laboratory if we want to comprehend habitability around M stars. The atmospheres of rocky planets can best be studied using these objects.

 

Comparison of the measured temperature of TRAPPIST-1b to Solar System objects and various models. (NASA, ESA, CSA, J. Olmsted/STScI, T. P. Greene/NASA Ames, T. Bell/BAERI, E. Ducrot & P. Lagage/CEA)

A red M-dwarf star 40 light-years distant and seven rocky exoplanets were found in the TRAPPIST-1 system in 2017. Three of those exoplanets are situated in the star's so-called habitable zone, which is the range of distances between the star's surface and the point at which all liquid water would either boil off or ice.

Although TRAPPIST-1 is a genuinely alluring target in the hunt for extraterrestrial life, there are some significant differences between it and the Solar System that raise doubts about the possibility of life there.

 

The planets orbiting this star are much closer to it than our own solar system, with the farthest planet having an orbit of only 18.8 days. The habitable zone is located much closer to red dwarf stars because they are smaller, colder, and dimmer than the Sun. The space around red dwarf stars, however, is blasted by strong flares because they are much more violent than the Sun.

According to astrophysicist Thomas Greene of NASA's Ames Research Center, there are ten times as many of these stars as there are stars like the Sun in the Milky Way and they are twice as likely to have rocky worlds.

 

However, they are also very vibrant when they are young and emit flares and X-rays that have the power to destroy an environment.

The first stage in figuring out how this activity might have impacted the system is TRAPPIST-1b. Although previous research using telescopes like Hubble and Spitzer had ruled out the presence of a thin, flimsy atmosphere surrounding the world, TRAPPIST-1b might still be home to a thick, dense atmosphere.

 

The infrared powers of JWST were most evident at this point. Utilizing TRAPPIST-1b's infrared light, which is produced by the exoplanet's thermal radiation, the researchers attempted to determine TRAPPIST-1b's temperature.

A diagram of the changes in a star's light as an exoplanet orbits. (J. Winn, arXiv, 2014)

The light curve that the exoplanet produces as it revolves around the star held the secret. The star's light dims a little amount when an exoplanet in orbit moves in front of us and blocks some of the star's light.

 

Dimming is also visible, however, when the extraterrestrial undergoes a secondary eclipse and moves behind the star.

 

This is so that more light from the system can be seen overall when the exoplanet is on either side of the star and reflecting some of the star's light in addition to releasing any radiation of its own. That implies that the star is the only source of light seen during the secondary eclipse.

Scientists can determine how much infrared radiation is emitted by the exoplanet itself and thus calculate its temperature by extracting the extra light that can be detected when the exoplanet is off to either side and the estimated reflected starlight. And this in turn can show whether there is an environment present or not.

 

According to CEA astronomer Pierre-Olivier Lagage, "This planet is tidally locked, with one side facing the star at all times and the other in perpetual darkness." The dayside will be cooler if there is an atmosphere to move the heat around and disperse it than if there isn't.

Five secondary eclipses of TRAPPIST-1b were observed by the researchers, and they were able to infer a dayside temperature of about 230 degrees Celsius from those occurrences. Even though this temperature is lower than Mercury's dayside in the Solar System, it does not meet the definition of an atmosphere.

 

We compared the outcomes to computer simulations that showed what the temperature should be in different scenarios, according to Ducrot.

"With a blackbody composed of bare rock and no atmosphere to move the heat, the results are almost exactly consistent. Additionally, we didn't observe any indicators of light absorption by carbon dioxide, which would have been visible in these observations.

In order to comprehend rocky planets orbiting red dwarf stars and how these systems differ from our own, future study, according to the researchers, could further characterise the global heat distribution of TRAPPIST-1b.

Reference: sciencealert.com