Artist conception of the exomoon Kepler-1625b I orbiting the exoplanet Kepler-1625b
A submoon (also known as a moonmoon, subsatellite, or grandmoon), is a natural or artificial satellite that orbits another natural satellite, i.e. a "moon of a moon".
The massive planet, Kepler-1625b, may possess a giant exomoon named Kepler-1625b I, which may possess submoons. In addition to submoons, it is possible that submoons could have their own set of moons - i.e. a subsubmoon. However, because tides prevent most moons from having their own moons, these would likely be restricted to very tiny moons, because everything would be squished closer together, making tides even stronger.
Possible submoons[]
Rhea[]
The possible detection of a ring system around Saturn's moon Rhea led to calculations indicating that satellites orbiting Rhea would have stable orbits. Furthermore, the suspected rings are thoughts to be narrow, a phenomenon normally associated with shepherd moons. However, images taken by the Cassini spacecraft have failed to detect any submoons or rings associated with Rhea.
Iapetus[]
It has also been proposed that another satellite of Saturn, Iapetus, possessed a submoon in the past. This is one of the several hypotheses that have been put forward to account for its unusual equatorial ridge.
Artificial satellite[]
Spacecraft has orbited the Moon in the past, including manned craft of the Apollo craft. As of 2018, none have orbited any other moons. In 1988, the Soviet Union unsuccessfully attempted to put two unmanned probes on quasi-orbits around the Martian moon Phobos.
See also[]
- Minor-planet moon