Click on image for full size
Image courtesy Dr. R. Albrecht (ESA/ESO Space Telescope European Coordinating Facility) and NASA.

Searching for more moons of Pluto
News story originally written on February 28, 2003

Astronomers are beginning to organize 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 Pluto is so far away (it is usually the furthest planet from the Sun) it is very difficult to see moons at that distance, even with the world's most powerful telescopes. Astronomers think earlier searches for other moons of Pluto could have missed moons as large as hundreds of kilometers across.

Scientists are preparing to launch a spacecraft, called the New Horizons mission, towards Pluto in a few years. Pluto is the only planet that has never been visited by a spacecraft, so we will learn a lot about Pluto when New Horizons gets there. The New Horizons mission is scheduled for launch in January 2006, but won't reach Pluto until sometime around 2015. Scientists working on New Horizons plan to search for more moons of Pluto using ground-based telescopes and possibly the Hubble Space Telescope. They expect to complete the search by the end of this year, and think they will be able to find moons as small as 10 to 20 kilometers across. If the scientists find more moons orbiting Pluto, they may want the New Horizons spacecraft to explore them.

Why do scientists think there might be more moons around Pluto? There have been many new discoveries of moons around planets in the outer solar system in recent years: 3 new moons of Neptune were found earlier this year, a new moon of Jupiter was found in 2002, 11 new moons of Jupiter were found in 2001, 11 new moons of Jupiter and 12 new moons of Saturn were found in 2000, and 4 new moons of Uranus were found in 1999. Also, astronomers have discovered several "moons" orbiting Kuiper Belt Objects (KBOs) in recent years. KBOs, which are also called Trans Neptunian Objects (TNOs), are large, icy spheres that orbit the Sun in the same general area as Pluto. Some types of comets originate in the Kuiper Belt. Most astronomers think that Pluto is just an especially large KBO, and since other KBOs have "moons", maybe Pluto has more than one moon. Some astronomers think Pluto is, in fact, "just" another KBO, and shouldn't really be considered a planet at all!


Last modified April 21, 2003 by Randy Russell.

You might also be interested in:

Pluto's Orbit

Pluto has the most eccentric orbit of all the planets in the solar system. The orbit draws within the orbit of Neptune, as can be seen in this drawing, making Pluto the 8th planet rather than the 9th...more

The Kuiper Belt

Thousands of frozen worlds hover at the edge of our Solar System. These frigid balls of ice and rock, similar in location and size to the planet Pluto, orbit the Sun in a distant region called the Kuiper...more

More and more Moons of Jupiter

Astronomers have discovered a dozen new moons of Jupiter so far in 2003. Scott Sheppard and David Jewitt of the University of Hawaii and Jan Kleyna of Cambridge University led the team of astronomers who...more

Mars Opposition in August 2003

On August 27, 2003, Earth and Mars will be closer together than they have been in thousands of years. The centers of the two planets will be 55,758,006 kilometers (34,646,418 miles) apart at 9:51 Universal...more

More Moons around Jupiter & Saturn

Astronomers have recently discovered several more moons in our Solar System. Scott Sheppard and David Jewitt of the University of Hawaii and Jan Kleyna of Cambridge University announced the discovery of...more

Mercury Transit on May 7, 2003

The planet Mercury appeared to cross in front of the disk of the Sun on May 7, 2003. Astronomers call the event a transit. A transit is similar to a solar eclipse. However, a transit occurs when a planet,...more

Space weather storms from the Sun

Two gigantic sunspot groups have recently appeared on the Sun and are generating tremendous space weather storms. The sunspot groups (known as group 484 and group 486) are about as large as the planet...more

More than 100 planets orbit distant stars!

Astronomers have identified another exoplanet, that is, a planet outside our solar system. This makes a total of 102 exoplanets that have so far been found by astronomers! The astronomers that identified...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