JWST could spot volcanic ‘exo-Ios’ around super-Jupiters

Jupiter’s moon Io is the most volcanically active planetary body in the solar system, boasting hundreds of active volcanoes that spew molten lava into space. This activity results from a process called tidal heating, in which Jupiter’s massive gravity constantly stretches and compresses the much smaller moon during its noncircular orbit.

However, a lesser-known fact is that Io’s volcanic gases fuel Jupiter’s auroras by traveling along the planet’s magnetic field lines and producing bright auroras observed by spacecraft and Earth-based telescopes. But what if this same phenomenon could be used to detect Io-like exomoons, also called exo-Ios, orbiting Jupiter-like exoplanets?

An international team of researchers might be one step closer to answering this question after introducing a novel method for potentially detecting and confirming the existence of exo-Ios. The study was recently accepted for publication in The Astronomical Journal and could help scientists identify exo-Ios and possibly other exomoons.

For the study, the researchers analyzed transit auroral data obtained by NASA’s James Webb Space Telescope (JWST) on exoplanet SIMP 0136+0933, which is located about 20 light-years (about 118 trillion miles) from Earth, has a mass of about 12.7 Jupiters and completes one rotation in only 2.4 hours. For context, Jupiter takes slightly under 10 hours to rotate once on its axis.

The researchers analyzed auroral data to determine whether a volcanically active exomoon could be “feeding” SIMP 0136+0933’s auroras, as Io is hypothesized to feed Jupiter’s auroras.

SIMP 0136+0933’s auroral data were obtained when it transited, or passed in front of, its host star, producing a light curve analyzed by JWST. In the end, the researchers found that SIMP 0136+0933 could potentially possess an exomoon, with estimated success rates for detecting an exo-Io or even an exo-Ganymede of 66% and 93%, respectively.

The study notes in its conclusions, “Although the existing light curves demonstrate that the transit technique is capable of detecting exosatellites analogous to Io in the aurorally active SIMP 0136+0933 system, the duration of the archival data is insufficient to place meaningful constraints on the presence of a transiting satellite. We conclude that JWST light curves spanning ∼1.5 days for ∼4–12 known aurorally active super-Jupiters would be needed to place meaningful statistical constraints on whether Io analogs are commonly present in these systems.”

Along with being designated a “super-Jupiter,” SIMP 0136+0933 is designated as a free-floating planetary-mass object. This differs from designation as a rogue planet because scientists classify it as being at the boundary between being too small to be a star and too large to become a planet. However, describing SIMP 0136+0933 as a rogue planet is still acceptable.

When it was discovered in 2006, SIMP 0136+0933 was designated a brown dwarf as part of a cluster of stars about 200 million years old. Brown dwarfs are also called “failed stars” because they did not become large enough to produce nuclear fusion. However, follow-up observations revealed that SIMP 0136+0933 was only 12.7 times Jupiter’s mass, making it too small to be a failed star.

This study comes as the scientific community has yet to definitively confirm the existence of an exomoon, though several unconfirmed exomoon candidates have been identified. These include candidates orbiting WASP-49 b, Kepler-1625 b, Kepler-1708 b and HD 206893 b. Exomoons are difficult to detect because of their significantly smaller size compared with exoplanets, making them analogous to microscopic dots in the bright glare of distant stars.

Who’s behind this story?

Swati Mestri

Swati Mestri holds a bachelor’s degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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