In a potential breakthrough discovery, NASA’s Jet Propulsion Laboratory (JPL) has identified a sodium cloud near the exoplanet WASP-49 b, which could indicate the presence of a volcanic exomoon—similar to Jupiter’s fiery moon Io. If confirmed, this would mark the first time an exomoon has been detected outside our solar system, opening new doors in our understanding of planetary systems beyond Earth. However, the team cautions that further observation and analysis are required before the existence of the exomoon can be confirmed.
Discovering a Volcanic Exomoon: Initial Evidence
The intriguing sodium cloud near WASP-49 b, a Saturn-sized gas giant 635 light-years away, was first detected in 2017. The discovery captivated researchers like Apurva Oza, who has been studying how volcanic activity on moons might leave clues in the form of gas clouds. In our own solar system, Jupiter's moon Io emits massive clouds of gas, including sodium, sulfur dioxide, and potassium, from its constant volcanic activity. Oza and his team have been investigating whether similar emissions could be observed from exomoons, even if the moons themselves are too small or faint to be seen with current technology.
"The sodium cloud doesn't match the composition of either the planet or the star, leading us to think there must be another source," Oza explained. That source, according to the team, might be a volcanic exomoon orbiting WASP-49 b.
Tracking a Mysterious Sodium Cloud
The cloud itself is remarkable, producing approximately 220,000 pounds (100,000 kilograms) of sodium per second. Both WASP-49 b and its star are largely made of hydrogen and helium, with trace amounts of sodium, but nowhere near enough to account for this massive cloud. This raised an exciting question: Could a volcanic exomoon be generating the sodium?
One of the key pieces of evidence pointing to a possible exomoon is the way the sodium cloud behaves. It doesn’t appear to be fully synchronized with the exoplanet or the star, moving in unexpected ways that suggest an independent source. Twice during the team's observations, the cloud suddenly grew in size, as if it had been “refueled” by something not directly related to the planet.
Moreover, the cloud seemed to move faster than the exoplanet itself, defying expectations if it were simply part of the planet’s atmosphere. "This movement doesn’t align with the physics of a planetary atmosphere," Oza noted. "It’s behaving as though it’s being driven by a separate body orbiting the planet."
Could It Be a Volcanic Moon?
The JPL team believes the sodium cloud could be the result of volcanic activity on a rocky exomoon orbiting WASP-49 b. This hypothetical moon might resemble Io, whose frequent volcanic eruptions create a similar sodium cloud that extends far beyond Jupiter.
Oza and his colleagues tested this theory using data from the European Southern Observatory's Very Large Telescope in Chile. By comparing the data to a computer model simulating the exomoon scenario, they found that an exomoon with a tight orbit—around eight hours long—could explain the cloud's odd behavior and movements.
Much like Io’s volcanic clouds, the sodium emissions from the potential exomoon seem to interact with the planet’s atmosphere and the surrounding space in complex ways, sometimes vanishing behind the star or planet only to reappear later. “Our model supports the idea that a fast-moving exomoon could be responsible for these patterns,” Oza said. However, he acknowledged that further observations are needed to confirm this theory.
A Closer Look at Planetary Systems
The discovery of a volcanic exomoon would offer invaluable insights into how planetary systems form and evolve. Volcanic activity, especially on moons, can significantly impact the atmospheres and environments of the planets they orbit. In our solar system, Io’s volcanic eruptions contribute to Jupiter’s magnetosphere and even its auroras. A similar process might be happening in the WASP-49 system.
Finding exomoons has been one of the great challenges in modern astronomy. Even though scientists have identified thousands of exoplanets, exomoons remain elusive. This is primarily because most moons are too small and faint to be detected directly, especially from hundreds or thousands of light-years away. But studying the gas clouds and other indirect evidence may offer a new path to discovery.
Future Prospects: Confirming the Exomoon’s Existence
While the research is still in its early stages, the JPL team hopes that further study of WASP-49 b and its sodium cloud will provide definitive proof of an exomoon’s existence. If confirmed, this would be a groundbreaking discovery, expanding our understanding of how moons influence their planets and revealing more about the complex interactions within distant planetary systems.
“We’re on the verge of a new era in planetary science,” said Oza. “Finding an exomoon is like discovering a missing piece of the puzzle. It gives us a more complete picture of the universe.”
In the years to come, scientists will continue to refine their tools and methods for detecting exomoons, opening the door to even more remarkable discoveries about the worlds beyond our own. As for WASP-49 b, it remains a tantalizing mystery, offering a glimpse of the volcanic forces that could be shaping not just planets, but entire star systems far from Earth.
