Searching for more moons of Pluto
News story originally written on February 28, 2003
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 Pluto is so far away (it is usually the furthest planet from the Sun) it is very difficult to see moons, 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. Scientists working on the New Horizons mission will use telescopes on Earth and maybe the Hubble Space Telescope to search for moons of Pluto this year. 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 the last few years: 41 new moons of Jupiter, Saturn, Uranus and Neptune have been found since the start of 1999. Also, astronomers have discovered several "moons" orbiting Kuiper Belt Objects (KBOs)in recent years. KBOs, are large, icy spheres that orbit the Sun in the same general area as Pluto. Some types of comets come from the Kuiper Belt. Some astronomers think Pluto isn't really a planet. They think Pluto is just a large KBO. Since other KBOs have "moons", maybe Pluto has more than one moon.