Astronomers have studied the vicinity of the planet WASP-49 b, located 635 light-years away from us. Surrounding the gas giant, scientists speculate, is a rocky volcanic moon resembling Jupiter's moon Io. No moon of a planet has ever been discovered beyond our Solar System. In this case, the only evidence that the distant gas giant possesses a moon is a sodium cloud orbiting the planet. A similar sodium cloud is also produced by Jupiter's moon. The research is published in the Astrophysical Journal Letters, reports Phys.
So far, moons of exoplanets have not been detected due to their small size and low brightness. However, scientists suggest that their existence can be inferred if some activity from these moons is observed, such as volcanic eruptions.
In our Solar System, Jupiter's moon Io is known for having the most volcanoes. As a result of volcanic eruptions, large amounts of sulfur dioxide, sodium, potassium, and other gases are expelled, creating a vast cloud around Jupiter.
The planet WASP-49 b is primarily composed of hydrogen and helium, with a small amount of sodium. Scientists believe this amount is insufficient to create a sodium cloud around it. Astronomers have found that the source of the sodium emission likely orbits the planet and is its volcanic moon, ejecting approximately 100,000 kg of sodium into space every second. However, additional observations are needed to confirm these findings.
Moreover, some evidence suggests that the sodium cloud was indeed created by the moon of WASP-49 b. For instance, scientists discovered that the cloud can suddenly increase in size, as if something near the gas giant is filling it with gaseous sodium. Additionally, the sodium cloud moves faster than the planet rotates and in the opposite direction, which would be impossible if the gas giant were the source.
According to scientists, if future observations confirm that WASP-49 b has a volcanic moon, it will be the first time a moon of a planet has been discovered outside our Solar System.
Volcanic eruptions on Io occur under the influence of Jupiter's gravity, which compresses the moon as it gets closer to the gas giant, and then releases the compression when Io moves away. As a result, Io's interior heats up, leading to active volcanism.
Calculations by scientists indicate that if WASP-49 b indeed has a moon similar in size to our Moon, the rapid loss of mass combined with the compression from the planet's gravity will ultimately lead to the moon's destruction.