Ceres
January 1801 Giuseppe Piazzi
4.6 470 10.6, 0.076 2.6, 3.0 0 Named for the Roman goddess of agriculture. Ceres in located in
the asteroid belt between Mars and Jupiter.
Pluto
February 1930 Clyde W. Tombaugh
248 1,188 17.2, 0.249 29.7, 49.3 5
Classified as a Plutino. A Plutino is a Kuiper belt object in a 2:3 orbital resonance with Neptune (for every 2 orbits a Plutino makes around the sun, Neptune orbits 3 times).
The International Astronomical Union's (IAU) names objects with a similar size and orbit to that of Pluto after underworld deities.
Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra. Pluto and Charon are sometimes considered a binary system because the barycenter of their orbits does not lie within either body.
Pluto is named for the Roman god of the underworld. Pluto's moon Charon is named after the ferryman of the underworld. Nix is the Greek goddess of darkness and night and mother of Charon, Hydra is the nine-headed serpent which battled Hercules, Kerberos in Greek mythology, is the many-headed dog that guarded the entrance to the underworld, and Styx is the river that souls had to cross over to get to Hades, or the underworld, and the goddess who ruled over it.
Ixion
May 2001 Deep Ecliptic Survey
250 309 19.6, 0.242 30.1, 49.6 0
Classified as a Plutino (see Pluto for definition).
Zeus invited Ixion to a banquet with other gods. Rather than being grateful, Ixion became lustful toward's Zeus's wife, Hera. Zeus found out about his intentions and created the cloud Nephele in the shape of Hera, and tricked Ixion into coupling with it, fathering the race of Centaurs. For his crimes, Ixion was expelled from Olympus, blasted with a thunderbolt, and bound to a burning solar wheel in the underworld for all eternity
Salcia September 2004 H. G. Roe M. E. Brown K. M. Barku 274 427 23.9, 0.11 37.7, 46.7 1
Classified as a Cubewano. A Cubewano is a low-eccentricity Kuiper belt object that orbits beyond Neptune and is not controlled by an orbital resonance with Neptune. Cubewanos have orbits with semi-major axes in the 40–50 AU range and, unlike Pluto, do not cross Neptune's orbit.
The International Astronomical Union's (IAU) names classical Kuiper belt objects (Cubewanos) after creator deities.
This minor planet was named after Salacia, the Roman goddess of salt water and the wife of Neptune.
The moon is named after Actaea a nereid or sea nymph.
2002 MS4 (Homonoia) June 2002 C. A. Trujillo M. E. Brown 272 400 17.7, 0.14 36.2, 47.9 0
Classified as a Cubewano (see Salcia for definition). The IAU has not yet assigned a name to the dwarf planet.
Homonoia is a proposed name. Homonoia was a minor Greek goddess of concord, unanimity, and oneness of mind.
Haumea (Santa) December 2004 (Brown et all) July 2005 (Ortiz et all) 283 780 28.2, 0.19 34.8, 51.6 2
Classified as a Cubewano (see Salcia for definition).
The discovery team used the codename "Santa" for the object, because of its discovery around Christmas time.
Brown initially conceded discovery credit to Ortiz, but came to suspect the Spanish team of fraud upon learning that his observation logs were accessed from the Spanish observatory the day before the discovery announcement.
Haumea is the Hawaiian goddess of fertility and childbirth, with many children who sprang from different parts of her body; this corresponds to the swarm of icy bodies thought to have broken off the main body during an ancient collision. The two known moons, also believed to have formed in this manner, are named after two of Haumea's daughters, Hiʻiaka and Nāmaka.
Haumea displays large fluctuations in brightness over a period of 3.9 hours, which can only be explained by a rotational period of this length. This is faster than any other known equilibrium body in the Solar System. Haumea rotates so quickly that it is distorted into a triaxial ellipsoid.
It is probably the third-largest known trans-Neptunian object, after Eris and Pluto.
Quaoar June 2002
C. A. Trujillo 286 555 8.0, 0.04 41.9, 45.5 1
Classified as a Cubewano (see Salcia for definition). Object X was the code name given to the object when it was discovered.
The team settled on selecting names from Native American mythologies local to the Palomar Mountain region, the location
Makemake (Easterbunny) March 2005 M. E. Brown C. A. Trujillo D. L. Rabinowitz 310 725 29, 0.16 38.1, 52.8 0
Classified as a Cubewano (see Salcia for definition).
The discovery team used the codename "Easterbunny" for the object, because of its discovery shortly after Easter.
The name of Makemake, the creator of humanity and god of fertility in the myths of the Rapa Nui, the native people of Easter Island, was chosen in part to preserve the object's connection with Easter. Gonggong (Snow White) July 2007 M. Schwamb M. E. Brown D. L. Rabinowitz 551 615 30.7, 0.5 33.7, 101.2 1
The discovery team used the codename "snow white" for the object because by the time of its discovery, Brown's team had discovered seven other large trans-Neptunian objects which were collectively referred to as the "seven dwarfs".
The object is named after Gònggōng, a Chinese water god responsible for chaos, floods and the tilt of the Earth. The name was chosen by its discoverers in 2019, when they hosted an online poll for the general public to help choose a name for the object, and the name Gonggong won.
The moon is named Xiangliu after the nine-headed poisonous snake monster that accompanied Gonggong in Chinese mythology.
Eris (Xena) January 2005 M. E. Brown C. A. Trujillo D. L. Rabinowitz 560 1,163 43.8, 0.44 38.3, 97.5 1
Eris's discovery was announced on July 29, 2005, the same day as Makemake and two days after Haumea due in part to events that would later lead to controversy about Haumea (see Haumea for discussion).
Eris was named after the Greco-Roman goddess of strife and discord.
Eris is the most massive and second-largest known dwarf planet in the Solar System.
"Xena" was an informal name used internally by the discovery team, inspired by the title character of the television series Xena: Warrior Princess.
In July 2015, after nearly ten years of Eris being considered the ninth-largest object known to directly orbit the sun, close-up imagery from the New Horizons mission more accurately determined Pluto's volume to be slightly larger than Eris's, rather than slightly smaller as previously thought. Eris is now the tenth-largest object known to directly orbit the sun by volume, but remains the ninth-largest by mass.
The moon received the name Dysnomia, after the Greek goddess of lawlessness who was Eris's daughter. Brown says he picked it for similarity to his wife's name, Diane.
Varda June 2003
J. A. Larsen 313 370 21.5, 0.14 39.5, 52.7 1
Classified as a Cubewano (see Salcia for definition).
Varda is the queen of the Valar, creator of the stars, one of most powerful servants of almighty Eru Iluvatar in J. R. R. Tolkien's fictional mythology. Ilmarë, the name of the moon, is a chief of the
