Scientists Make Surprising Discovery in Exoplanet’s Atmosphere

By Lydia Amazouz Published on June 13, 2024 13:30
Scientists Make Surprising Discovery In Exoplanet's Atmosphere

A recent discovery by the James Webb Space Telescope (JWST) has revealed the presence of sulfur dioxide (SO₂) in the atmosphere of the exoplanet GJ 3470b, challenging existing theories of planet formation.

Located 96 light-years from Earth, GJ 3470b is a "hot Neptune" that completes an orbit around its cool red dwarf star every 3.3 days. This discovery has profound implications for our understanding of atmospheric chemistry on exoplanets and their formation processes.

The presence of sulfur dioxide, a molecule unexpected in such a small and cool exoplanet, adds a new dimension to the study of planetary atmospheres, prompting scientists to revisit and refine their models of planetary formation and chemical processes.

Details about the Sulfur Dioxide Detected in Atmosphere of Exoplanet GJ 3470b

The detection of sulfur dioxide in the atmosphere of GJ 3470b came as a surprise to astronomers. Typically, this molecule is found in much larger and hotter exoplanets, such as hot Jupiters, making its presence in a smaller and cooler planet unexpected.

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Finding So2 Was A Surprise Because Gj 3470 B Is The Smallest And Coolest Exoplanet To Have The Compound In Its Atmosphere. Image Credit Beatty Et Al. 2024

Thomas Beatty, an astronomer at the University of Wisconsin, Madison, and the lead researcher on this study, emphasized the significance of this finding: "We didn’t think we’d see sulfur dioxide on planets this small, and it’s exciting to see this new molecule in a place we didn’t expect since it gives us a new way to figure out how these planets formed."

This discovery provides a new perspective on the atmospheric compositions of smaller exoplanets and their evolutionary histories. It suggests that the processes leading to the formation and chemical composition of planetary atmospheres are more diverse and complex than previously thought.

The JWST's sophisticated instruments allowed for the detection of sulfur dioxide through transmission spectroscopy, a method where light from the parent star passes through the planet's atmosphere, revealing the chemical composition based on the absorption lines in the spectrum.

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Unique Orbital Characteristics

GJ 3470b exhibits unique orbital characteristics that further intrigue scientists. Unlike most planets that form in a disk aligned with their star’s rotational axis, GJ 3470b orbits at a steep inclination of 89 degrees to its star’s axis, looping over the star’s poles.

This unusual orbit suggests a turbulent history, potentially involving gravitational interactions with other planets or even a close-passing star. Such an orbit is atypical for planet formation and adds another layer of mystery to GJ 3470b’s origins.

Planets typically form in a more stable, equatorial plane; thus, the steep orbit of GJ 3470b implies significant dynamical interactions during its history.

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These interactions could have included close encounters with other planetary bodies or even a stellar flyby, which could have altered its orbit dramatically. Understanding these interactions is crucial for constructing accurate models of planetary system evolution.

Atmospheric Composition and Formation Theories

The atmosphere of GJ 3470b, predominantly composed of hydrogen and helium, is also unusual. Previous observations by the Hubble Space Telescope indicated an atmosphere richer in these lighter elements than those of the gas giants in our solar system.

The JWST's detection of sulfur dioxide, along with other molecules like carbon dioxide, methane, and water vapor, offers vital clues about the planet’s formation. Scientists hypothesize that GJ 3470b may have formed closer to its star as a rocky planet before accumulating a thick atmosphere of hydrogen and helium.

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This is a departure from the traditional view that gas giants form farther from their stars and migrate inward. This hypothesis is supported by the planet’s current close proximity to its star, which is only 5.3 million kilometers away, much closer than Mercury's distance to the Sun.

The planet’s current atmospheric composition, dominated by hydrogen and helium, combined with the presence of sulfur dioxide, suggests that complex chemical processes have been at play since its formation.

Implications of Sulfur Dioxide Detection

The presence of sulfur dioxide in GJ 3470b's atmosphere could be a result of photochemical reactions driven by ultraviolet light from its star. This light breaks apart hydrogen sulfide molecules, freeing sulfur atoms that then combine with oxygen to form sulfur dioxide.

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The significant amount of sulfur dioxide found, about one million times more than expected, suggests complex chemical processes at play. This discovery not only helps differentiate between various formation theories but also enhances our understanding of atmospheric chemistry in diverse planetary environments.

The presence of sulfur dioxide in such unexpected quantities indicates that photochemical reactions are occurring at a much higher rate than predicted. This could be due to the planet’s close proximity to its star, where intense radiation provides the energy needed for these reactions. Additionally, the high metallicity of GJ 3470b’s atmosphere, about 100 times more than WASP-39b, enables sulfur dioxide-producing reactions at much lower temperatures.


An editor specializing in astronomy and space industry, passionate about uncovering the mysteries of the universe and the technological advances that propel space exploration.

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