Using the James Webb Space Telescope (JWST), astronomers have confirmed that TRAPPIST-1b is unlikely to have an atmosphere. The researchers were excited to use the new telescope to study the telescope and its six siblings, all of which are roughly the size of Earth and orbit a star 12 parsecs (39 light-years) from Earth.
The system is a unique laboratory for studying how environmental conditions are created on planets – and how they can become suitable for life. Last November and December, JWST searched for the atmosphere on TRAPPIST-1b by looking for the heat it radiated.
Although the finding may sound disappointing to atmospheric hopefuls, the researchers say the work shows the transformative power of JWST and opens the door for more results from the TRAPPIST-1 system.
Previous studies with the Hubble and Spitzer Space Telescopes using a different technique have shown that TRAPPIST-1b the innermost planet in the system probably does not have a large puffy atmosphere made up mostly of hydrogen2. However, scientists could not rule out whether it has a thick atmosphere like Earth had billions of years ago.
Planetary Laboratory
JWST looked at TRAPPIST-1 in mid-infrared wavelengths of light 20 times redder than the human eye can see—to see how that radiation changed as TRAPPIST-1b moved behind the star. By measuring the brightness of the star and planet together compared to the brightness of the star itself, astronomers could calculate how much came from the planet.
If TRAPPIST-1b had an atmosphere, it would recirculate energy absorbed from the star and appear less bright than Greene and his colleagues measured. The observations revealed no carbon dioxide on the planet that JWST could detect.
M dwarf stars cool
Not surprisingly, TRAPPIST-1b has no atmosphere, as it emits four times the radiation that Earth receives from the Sun. TRAPPIST-1 is also destroyed by stellar eruptions and other activity that sends radiation across its planets and potentially destroys the atmosphere. However, understanding these conditions is critical because M dwarf stars cool, dim stars like TRAPPIST-1—often have Earth-sized planets orbiting them.
A key early step in studying the TRAPPIST-1 system is to harness the power of JWST to understand the star itself, says Julien de Wit, an exoplanet researcher at the Massachusetts Institute of Technology in Cambridge: ‘know your star’ should come before know your planets.” Astronomers should to collaborate on the TRAPPIST-1 study with JWST using a variety of techniques to understand the star as completely as possible, he says.
Otherwise, researchers will struggle to interpret what they see in planetary observations because the star’s activity could contaminate those measurements.
More discoveries will surely come. Other research teams are using JWST to study TRAPPIST-1b, as well as other planets in the system. This includes TRAPPIST-1b’s neighbor, TRAPPIST-1c, a planet close enough to its star for JWST to study its glow. Publications on all of them are expected soon.
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Reference : https://www.nature.com/articles/d41586-023-00876-7
