This picture shows Pluto (left) and its big moon Charon (right). Notice how big Charon is compared to Pluto. Notice how close Charon is to Pluto. This picture was taken by the Hubble Space Telescope in 1994.
Click on image for full size
Image courtesy Dr. R. Albrecht (ESA/ESO Space Telescope European Coordinating Facility) and NASA.

The Moons of Pluto

Pluto has moons. One of the moons is very large. The large moon is named Charon. The other two moons are fairly small. They don't really have names yet. For now they are called S/2005 P1 and S/2005 P2.

Charon is nearly as big as Pluto. Some astronomers call Pluto and Charon a double planet. James Christy discovered Charon in 1978.

S/2005 P1 and S/2005 P2 were discovered in 2005. A team of astronomers led by Alan Stern and Harold Weaver found the moons. The team was looking for new moons of Pluto using the Hubble Space Telescope. They were getting ready for the New Horizons space mission to Pluto. S/2005 P1 is about 150 km (93 miles) across. S/2005 P2 is even smaller, about 100 km (62 miles) across. S/2005 P1 takes 38 days to go around Pluto. S/2005 P2 orbits Pluto every 25 days.

S/2005 P1 and S/2005 P2 will get "real" names after astronomers observe them a few more times. They want to make sure they are moons of Pluto before they give them permanent names.

We don't know whether Pluto has rings or not. Nobody has seen any rings around Pluto so far.

Last modified January 23, 2006 by Randy Russell.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more


Pluto is a frigid ball of ice and rock that orbits far from the Sun on the frozen fringes of our Solar System. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...more

Charon - Pluto's biggest moon

Charon is a moon of Pluto. Pluto has // Call the moon count function defined in the document head print_moon_count('pluto'); moons. Charon is much larger than Pluto's other moons. James Christy discovered...more

Pluto & Charon, a double planet

Of all the planets and moons in the solar system, Pluto and Charon are the two which resemble each other the most closely. They are almost the same size, and they are very close together. They are so...more

Hubble Space Telescope

The Hubble Space Telescope (HST) was one of the most important exploration tools of the past two decades, and will continue to serve as a great resource well into the new millennium. The HST found numerous...more

Searching for more moons of Pluto

Astronomers will soon start a search for more moons of Pluto. Pluto has only one known moon, Charon, but astronomers think there might be other moons orbiting Pluto that haven't yet been discovered. Because...more

Makemake: a Dwarf Planet

Makemake is a dwarf planet in our Solar System. Makemake was discovered in March 2005 by a team of astronomers led by Mike Brown. Makemake officially became a dwarf planet in July 2008. There were three...more

Questions to answer about Pluto

Pluto is so far away, and has never been explored. Questions to answer about Pluto include the following: What are the geologic features of the surface. (pictures of the surface) If there are bare spots,...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA