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Gravity is a force that
pulls objects together.
It holds us down on the
Earth, and the Moon in
orbit around the Earth.
The more massive and
closer an object is, the
greater its gravitational
pull or attraction.
Gravity Sucks!
Pluto is the dwarf planet in the outer reaches of the Solar System.
Pluto was discovered in 1930 by Clyde Tombaugh, and until 2006 was considered to be the ninth planet. It now lends its name to a class of objects, known as plutoids, which are dwarf planets that circle the Sun beyond the orbit of Neptune.
Pluto's has a very eccentric orbit. This means that it follows a stretched out oval-shaped path during its 248 year travels around the Sun, rather than a circular one. Its orbit is also inclined to the plane of the solar system by around 17°.
Astronomers have found 3 moons around Pluto. The largest, Charon, is around half Pluto's size, whereas the remaining two, Hydra and Nix, are much smaller.
Pluto has never been visited by a space-probe, so we don't really know what it looks like, but this will change in 2015 with the arrival of NASA's New Horizons probe.
| Facts and Figures | Ceres | Pluto | Haumea | Makemake | Eris |
| Orbital distance (AU)1 | 2.77 | 39.5 | 43.1 | 45.8 | 67.7 |
| Orbital Inclination | 10.6° | 17.1° | 28.2° | 29° | 44° |
| Radius (KM) | 487 | 1,137 | 1,436 | 750 | 1,300 |
| Mass (Earth Masses)2 | 0.00016 | 0.00213 | 0.0007 | 0.0007 | 0.003 |
| Year Length (Earth Years) | 4.6 | 248.5 | 283.3 | 309.9 | 557 |
| Day Length (Earth Days) | 0.38 | 6.39 | 0.16 | Unknown | Unknown |
| Surface Gravity (g)3 | 0.003 | 0.04 | 0.044 | 0.05 | 0.08 |
| Surface Temperature | about -105°C | about -230°C | about -240°C | about -243°C | about -240°C |
| Number of moons | 0 | 3 | 2 | 0 | 1 |
