JWST just discovered Methane on a distant exoplanet

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In a groundbreaking discovery, NASA’s James Webb Space Telescope (JWST) has detected methane in the atmosphere of WASP-80b, a distant exoplanet approximately half the mass of Jupiter.

This discovery is significant due to methane’s potential as a biosignature, although its presence alone doesn’t confirm biological activity since methane can have both biotic and abiotic origins. Methane is particularly interesting to scientists because it doesn’t last long in planetary atmospheres without being replenished, as it breaks down under starlight.

WASP-80b, orbiting a K-type main sequence star about 1.5 billion years old and located approximately 162 light-years from Earth, is a warm Jupiter-like exoplanet with a surface temperature of about 550 Celsius. This temperature places WASP-80b in a unique category, different from the extremely hot or cold Jupiters known previously, making it a key subject for further research in atmospheric chemistry.

When viewed with human eyes, the warm exoplanet WASP-80 b’s color may appear bluish due to the lack of high-altitude clouds and the presence of atmospheric methane identified by NASA’s James Webb Space Telescope. That makes it similar to the planets Uranus and Neptune in our own solar system. (NASA.)

The planet’s proximity to its red dwarf star, completing an orbit in just three days, means that the JWST cannot directly observe it. Instead, the telescope analyzes the combined light from the star and the planet during transits and eclipses. Previously, telescopes like Hubble and Spitzer had limited success in detecting methane in exoplanet atmospheres, leading scientists to theorize about potential methane depletion mechanisms. However, JWST’s discovery challenges these theories and suggests that previous non-detections might have been due to the limited capabilities of earlier instruments.

This image shows the measured transit spectrum (top) and eclipse spectrum (bottom) of WASP-80 b from the JWST’s NIRCam. In both spectra, there is clear evidence for absorption from water and methane. During a transit, the planet passes in front of the star, and in a transit spectrum, the presence of molecules makes the planet’s atmosphere block more light at certain colours, causing a deeper dimming at those wavelengths. During an eclipse, the planet passes behind the star, and in this eclipse spectrum, molecules absorb some of the planet’s emitted light at specific colours, leading to a smaller dip in brightness during the eclipse compared to a transit. (BAERI/NASA/Taylor Bell)

This detection not only advances our understanding of WASP-80b but also has broader implications for our knowledge of the solar system and exoplanet atmospheres. The presence of methane alongside water in the atmosphere of WASP-80b can provide insights into the planet’s formation, indicating the ratio of carbon to oxygen atoms and potentially revealing whether the planet formed close to its star or migrated inward from a more distant orbit.

Future observations with JWST’s NIRCam and MIRI instruments are expected to reveal more about the planet’s atmosphere, potentially detecting other carbon molecules like carbon monoxide and carbon dioxide. This research highlights methane’s role beyond a potential biosignature, as it can help understand planetary formation and migration processes.

Overall, the detection of methane in WASP-80b’s atmosphere is a significant milestone in exoplanetary science, showcasing the JWST’s capabilities and opening new avenues for understanding the atmospheres and formation histories of distant worlds.

Reference(s): NASA, Research Paper

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