Dwarf Planet Moons

Dwarf Planets	confirmed moons	provisional moons	Total
Pluto	5	0	5
Eris	1	0	1
Haumea	2	0	2
Makemake	0	1	1
Ceres	0	0	0

Moons of Dwarf Planets

Pluto’s large moon Charon is about half the size of Pluto. Like Earth’s Moon, Charon may have formed from debris resulting from an early collision of an impactor with Pluto. Scientists using the Hubble Space Telescope to study Pluto found four more small moons.

Eris, another dwarf planet even more distant than Pluto, has a small moon of its own, named Dysnomia. Haumea, another dwarf planet, has two satellites, Hi’iaka and Namaka. Ceres, the closest dwarf planet to the Sun, has no moons.

This composite image shows a sliver of Pluto’s large moon, Charon, and all four of Pluto’s small moons, as resolved by the Long Range Reconnaissance Imager (LORRI) on the New Horizons spacecraft. Image Credit: NASA/JHUAPL/SwRI

It is intriguing that such a small planet can have such a complex collection of satellites. The discovery provides additional clues for unraveling how the Pluto system formed and evolved.

Pluto’s entire moon system is believed to have formed by a collision between two the dwarf planet and another Kuiper Belt Object early in the history of the solar system. The smashup flung material that coalesced into the family of satellites observed around Pluto.

“The moons form a series of neatly nested orbits, a bit like Russian dolls,” said Mark Showalter of the SETI Institute.

The known moons of Pluto are:

Charon: Discovered in 1978, this small moon is almost half the size of Pluto. It is so big Pluto and Charon are sometimes referred to as a double planet system.
Nix and Hydra: These small moons were found in 2005 by a Hubble Space Telescope team studying the Pluto system.
Kerberos: Discovered in 2011, this tiny moon is located between the orbits of Nix and Hydra.
Styx: Discovered in 2012, this little moon was found by a team of scientists searching for potential hazards to the New Horizons spacecraft Pluto flyby in July 2015.

How Pluto Moons Get Their Names

All of Pluto’s moons are named for mythological figures associated with the underworld, a naming conventions started by 11-year-old Venetia Burney in 1930

Eris has a very small moon called Dysnomia. Dysnomia has a nearly circular orbit lasting about 16 days. This moon is named after Eris’ daughter, the demon goddess of lawlessness.

Dysnomia and other small moons around planets and dwarf planets allow astronomers to calculate the mass of the parent body. Dysnomia plays a role in determining how comparable Pluto and Eris are to each other.

Haumea has two known moons: Namaka is the inner moon, and Hi’iaka is the outer moon. Both are named for the mythological daughters of Haumea. Hi’iaka is the patron goddess of the island of Hawaii and of hula dancers. Namaka is a water spirit in Hawaiian mythology.

Makemake has one provisional moon, S/2015 (136472) 1, and it’s nicknamed MK 2. It is more than 1,300 times fainter than Makemake. MK 2 was seen approximately 13,000 miles from the dwarf planet, and its radius is estimated to be about 50 miles (80 kilometers).