A giant sodium cloud surrounding an exoplanet located 635 light-years away could point towards a highly active volcanic moon. If confirmed, this would be the first known discovery of an exomoon. The research findings were gathered by a team led by planetary scientist Apurva Oza from the California Institute of Technology after the presence of the cloud was first detected in 2017. The sodium source is theorized to produce 100 tons per second, emanating from the exoplanet, suggesting highly promising evidence. Further analysis shows that the sodium cloud moves faster than the exoplanet, expanding as if being refilled, indicating the presence of a moon.

A Second Io?

These observations remind researchers of Jupiter's moon Io, the most volcanically active celestial body in our solar system. Io is constantly compressed by Jupiter's gravity, releasing sulfur dioxide, sodium, potassium, and other gases into space, forming clouds larger than Jupiter itself. The team suspects a similar phenomenon with exoplanet WASP-49 b, which mainly consists of hydrogen and helium, and minor sodium quantities, insufficient to justify the cloud's immense size. Additionally, there's no known mechanism for the exoplanet to expel such quantities of sodium into space, suggesting a volcanically active exomoon's presence.

Supporting Computer Models

Research indicates the sodium cloud is situated significantly above the planet's atmosphere, moving in a manner unrealistic for atmospheric components. Computer simulations suggest a moon completing orbiting every eight hours could account for these movements and activities. The tidal forces may deform the moon similarly to Io, leading to significant mass loss and possibly a violent eventual disintegration. However, this remains a hypothesis, and the search for definitive exomoon traces continues. The work is published in the Astrophysical Journal Letters.

This sodium cloud presents a novel indication of an exomoon, differing from previous suggestions based on star dimming potentially caused by orbiting moons. Those theories faced criticism, claiming other explanations are likely. Two astronomers argue current technology only allows discovery of moons vastly different from the 300+ in our solar system, a limitation not applicable to Oza's team’s approach.

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