Editorial Feature

JWST Finds Methane in Exoplanet Atmosphere

Methane is the only detectable biosignature in terrestrial atmospheres using the James Webb Space Telescope (JWST). Hence, detecting the presence of methane in an exoplanet's atmosphere is crucial for studying its potential habitability. A recent article published in Nature reported the presence of exoplanetary methane in the WASP-80b atmosphere, a Jupiter-like exoplanet.

Exoplanet Atmosphere, JWST, exoplanets

Image Credit: Telepaths/Shutterstock.com

New Frontiers in Exoplanetary Science

Exoplanetary science investigations have advanced from a simple quest for extraterrestrial planets to their atmospheric characterization. This information about distant worlds can help comprehend the formation and migration of planets because the evolutionary path of a planet shapes the composition of atmospheric gases.

While the explanatory science investigations have mainly concentrated on carbon- and oxygen-rich molecules, methane remains a relatively unexplored molecule in the exoplanetary atmosphere that closely orbits around its host star.

A research group at the National Aeronautics and Space Administration (NASA), led by a postdoctoral research scientist, Taylor James Bell, has marked a significant milestone in using the JWST to obtain evidence of methane existence in the atmosphere of the Jupiter-like exoplanet, WASP-80b.

What is WASP-80b?

WASP-80b is a gas giant exoplanet whose size is approximately the same as that of Jupiter, but its mass is only about half of it. This exoplanet orbits about every three days around a K-type star, showing only its dayside.

WASP-80b is the hottest planet in the Solar System, with a temperature of 800 kelvin. However, in terms of exoplanets, WASP-80b is considered a warm planet because the extreme conditions in exoplanets can reach up to 5000 kelvin.

Since its discovery in 2012, WASP-80b has been a promising candidate for studying exoplanetary atmospheres, carried out using both space- and ground-based telescopes. While studies conducted using these telescopes revealed the presence of water and carbon dioxide, the presence of methane was detected only by the ground-based instrument, JWST, in the WASP-80b atmosphere.

Significance of Methane Detection

Methane is an exoplanet biosignature, and its presence in an exoplanet's atmosphere predicts potentially habitable planets. Detecting the presence of methane reveals the carbon content of the giant planet in the Solar System and provides clues on its habitability.

Thus, the accurate measurement of methane in the atmosphere of planets outside our Solar System can help compare our gas giants with those around other stars. This information is crucial for understanding the formation and movement of these planets.

Just as the existence of water on the surface of a planet predicts a plausible life, methane in the atmosphere could also be a possible signal. However, methane alone is not enough to predict whether a planet can support life because this molecule can also hail from a non-biological process.

However, its existence as a mixture of other sources, such as carbon dioxide, could make it difficult to explain its origin from a non-biological source. The presence of methane is particularly interesting when it is present in an atmosphere with minimal carbon monoxide, as CO is consumed by microbes. Thus, the detection of methane in WASP-80b by the research group is a substantial milestone in exoplanetary science.

Methodology and Findings

Generally, directly analyzing a planet’s atmosphere is the first step in exoplanetary science. However, for WASP-80b-like planets, whose stars are at closer distances, direct observation of the atmosphere becomes difficult because the stars are brighter than the planets and hence hide them.

Therefore, to determine the atmosphere of WASP-80b, a comparative technique was used in the present study. They first observed the WASP-80b exoplanet atmosphere at its terminator. Here, the initial focus of the JWST was made only on the star to record the spectrum of the light emitted from it. Subsequently, another spectrum was recorded when the star and WASP-80b crossed their paths.

Each component of the atmosphere absorbs light emitted by a star with a unique fingerprint. Thus, by comparing the spectra of WASP-80b and its star followed by the analysis of missing frequencies during the transit, the researchers inferred the composition of the WASP-80b's atmosphere at its terminator.

In addition, the team measured the dayside of the planet. For this, the JWST was focused on observing the WASP-80 system when the planet was masked by the star during the secondary eclipse, which helped obtain the star’s spectrum alone.

Comparing the star’s spectrum, which was obtained during the eclipse, and the merged spectrum of the star and planet helped separate the spectrum of the planet’s dayside, and consequently, the planet’s atmospheric composition was determined.

These observations confirmed the presence of water and methane at both the dayside and terminator of the planet. Moreover, the methane concentration in the atmosphere was the same in both regions, indicating that the planet's atmosphere was well mixed.

The research findings revealed that WASP-80b’s atmospheric composition in terms of heavy metal concentration and carbon-to-oxygen ratio was different from that of the sun. However, the obtained measurements lacked the precision to speculate the formation pathway of the planet, necessitating sophisticated telescopes with a broader wavelength range.

The inability of previously used telescopes to find methane was overcome by using JWST because of the availability of a broad wavelength range in the latter, suggesting the re-evaluation of planets previously observed using space-based telescopes.

Conclusion

Overall, exoplanetary science has evolved from merely discovering planets beyond our Solar System to aiding in atmospheric characterization. The present study utilized the JWST to detect methane in the atmosphere of WASP-80b, which marks a significant milestone. This finding not only concluded the search for exoplanetary methane but also highlighted the remarkable capabilities of the JWST in observing the atmosphere of the exoplanet.

WASP-80b, with its peculiar characteristics of orbiting a small red star, is an ideal candidate for atmospheric studies. The confirmation of methane in its atmosphere offers a basis for comparing giant planets in our Solar System with those orbiting other stars, shedding light on their formation and migration pathways.

Additionally, the presence of methane, combined with other gases such as carbon dioxide, suggests potential biological activity, although its presence alone is insufficient to claim habitability. Thus, this discovery opens doors for further exploration, promising invaluable insights into exoplanet formation, comparative planetary studies, and assessing potential habitability.

More from AZoM: How Organic Hazes from Water-Rich Exoplanet Atmospheres Impact JWST Observations

References and Further Reading 

Guilluy, G. (2023). JWST ends the game of hide and seek with methane. Nature 623, 697-698 https://doi.org/10.1038/d41586-023-03500-w

Thompson, M. A., Krissansen-Totton, J., Wogan, N., Telus, M., Fortney, J. J. (2022). The case and context for atmospheric methane as an exoplanet biosignature. Proceedings of the National Academy of Sciences, 119(14). https://doi.org/10.1073/pnas.2117933119

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Bhavna Kaveti

Written by

Bhavna Kaveti

Bhavna Kaveti is a science writer based in Hyderabad, India. She has a Masters in Pharmaceutical Chemistry from Vellore Institute of Technology, India, and a Ph.D. in Organic and Medicinal Chemistry from Universidad de Guanajuato, Mexico. Her research work involved designing and synthesizing heterocycle-based bioactive molecules, where she had exposure to both multistep and multicomponent synthesis. During her doctoral studies, she worked on synthesizing various linked and fused heterocycle-based peptidomimetic molecules that are anticipated to have a bioactive potential for further functionalization. While working on her thesis and research papers, she explored her passion for scientific writing and communications.

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