[NARRATOR] A rocky volcanic moon
could be orbiting a planet more than 600 light-years from Earth.
Exomoons or moons around planets outside our solar system
are likely too small to see directly,
but astronomers think volcanic exomoons
could make themselves known
by creating massive clouds of volcanic gas.
A new study looked at a large sodium cloud
discovered in 2017
near the exoplanet WASP-49b.
Scientists found evidence that the cloud is not produced
by the planet, or the star it orbits.
Instead, the motion of the cloud suggests it originated
from another object,
possibly a volcanic exomoon.
To get to this conclusion, researchers used
a telescope on Earth to observe the silhouettes of the cloud
and the exoplanet as they passed in front of the star.
In one observation, the researchers saw the sodium cloud
moving faster than the planet and away from Earth.
If the cloud was coming from the exoplanet,
the scientists would expect it to move toward Earth.
They think this means the cloud
was coming from a different source, like an exomoon.
Jupiter's moon Io
also spews a volcanic cloud into space.
It pumps sodium, sulfur and other gases,
cloud a massive cloud a thousand times wider than Jupiter.
Io has volcanoes because Jupiter's
gravity squeezes the moon's interior, heating it.
Scientists think WASP-49b's gravitational squeezing
is likely even more intense
and may eventually cause its exomoon to disintegrate.
While more observations
are needed to confirm the existence of this exomoon,
what researchers have found is promising.