The James Webb Space Telescope yesterday detected the temperature of a rocky exoplanet for the first time. Also revealing that a “cousin” of Earth most likely does not have an atmosphere.
When the Trappist-1 system was found in 2017, astronomers were ecstatic because some of its seven rocky planets. Which are approximately the size and mass of Earth, could be habitable.
The planets circle their ultracool red dwarf star much closer than the rocky planets in our Solar System. Which is only 40 light years away. However, their star emits far less energy than our Sun.
The system was an obvious target for the Webb telescope’s piercing gaze. Which has released a flood of scientific discovery since releasing its first observations in July last year.
Because Trappist-1b was the nearest planet to the red dwarf. Astronomers concentrated their efforts on it.
Webb’s Mid-Infrared Instrument (MIRI) measured the brightness shift as the planet moved behind its star in a secondary eclipse.
“The planet gives off the most light just before disappearing behind the star because it almost exclusively shows its ‘day’ side,” Elsa Ducrot, a co-author of a new study published in the journal Nature, told AFP.
The amount of infrared light emitted by the planet was determined by subtracting the brightness of the star.
As a result, the MIRI device could function as “a giant touch-free thermometer,” according to NASA.
“Just about perfect for baking pizza,”
The planet’s dayside temperature was determined to be 230 degrees Celsius (450 Fahrenheit) — “just about perfect for baking pizza,” NASA added.
France’s Atomic Energy Commission (CEA) said that the heat was not redistributed throughout this “cousin” of Earth, a role normally provided by an atmosphere.
The scientists therefore concluded that Trappist-1b “has little or no atmosphere,” said Ducrot, a CEA astrophysicist. She emphasised that other wavelengths would need to be analysed to confirm the result.
But it was certain that the atmosphere did not contain carbon dioxide, because that would have absorbed some of the light, she added.
The Spitzer Space Telescope was not able to rule out an atmosphere on Trappist-1b despite observing 28 secondary eclipses, Ducrot said.
“The James Webb telescope saw rocky exoplanet in a single eclipse!”
The ability to analyse the potential atmospheres of such rocky exoplanets opens “a new era” in the study of planets outside our Solar System, she added.
It was already known that Trappist-1b was uninhabitable, as it is too close to its star.
But Trappist-1e, Trappist-1f and Trappist-1g are all thought to be in what is called the “goldilocks zone”.
Planets in this zone have a moderate temperature which could support liquid water — considered essential for life anywhere.
