There are 288 discovered natural satellites – or moons, as they are colloquially known – in the Solar system. Most of these are found in the outer gas giants. However, many of these have not received proper names as they were discovered recently and have yet to be confirmed. Only 164 moons have proper names.
Out of those, there are 3 moons whose names start with the letter O. These are all listed in the following table. Below you will also find some additional details about each, including physical characteristics, the original meaning of their names, etc.
| Name | Planet | Name meaning |
|---|---|---|
| Oberon | Uranus | Named after a charcter in Shakespeare’s play A Midsummer Night’s Dream |
| Ophelia | Uranus | Named after a charcter in Shakespeare’s play Hamlet |
| Orthosie | Jupiter | Greek goddess of prosperity and one of the Horae. |
Oberon
Oberon, discovered by William Herschel in 1787, is the outermost of Uranus’s five major moons. Named after the King of the Fairies in Shakespeare’s A Midsummer Night’s Dream, it’s the second-largest Uranian moon at 1,523 kilometers in diameter. Its surface is heavily cratered and characterized by dark patches of unknown material, possibly organic compounds exposed by meteorite impacts. The moon features a prominent mountain that rises about 6 kilometers above the surface, and its largest crater, Hamlet, is about 206 kilometers across.
Ophelia
Ophelia, discovered in 1986 by the Voyager 2 imaging team, is one of Uranus’s small inner moons. Named after the tragic heroine in Shakespeare’s Hamlet, this tiny moon is only about 43 kilometers in diameter. It serves as one of the shepherd moons of Uranus’s epsilon ring, helping to confine and maintain the ring’s narrow width through gravitational interactions. Along with Cordelia, it helps keep the epsilon ring’s particles in a stable orbit.
Orthosie
Orthosie is a small irregular moon of Jupiter discovered in 2001 by Scott Sheppard and a team of astronomers at the University of Hawaii. Named after one of the Horae (Hours), the Greek goddess of prosperity and seasonal change, it’s approximately 2 kilometers in diameter. It belongs to the Ananke group of irregular satellites, orbiting Jupiter in a retrograde direction, suggesting it was likely captured rather than formed alongside Jupiter. Its small size and distant, irregular orbit make it one of Jupiter’s more challenging moons to study.
Click on a letter below for a list of moons that begin with it.
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Related:
For more on how moons are named check out this article.