KBO stands for Kuiper Belt Object. The Kuiper Belt lies between around 30 AU and 55 AU from the Sun, starting outside the orbit of Neptune. (One AU being the Earth’s orbital radius.) The Kuiper Belt comprises thousands of comet like bodies that remain in a state of deepfreeze for billions of years. The Kuiper Belt is similar to The Asteroid Belt in shape, but is much wider. The Kuiper Belt is home to three of the five Dwarf Planets currently recognised by the International Astronomical Union (IAU). These are Pluto, plus the recent editions of Makemake (pronounced “mak-ee mak-ee”) and Haumea “how-may-a”. Ceres being in The Asteroid Belt, and Eris being in the Scattered Disc, a region of space beyond the Kuiper belt. The difference between a Dwarf Planet and a regular planet is that a Dwarf Planet has not cleared its orbital path of debris, i.e. the Asteroid Belt in the case of Ceres, and the Kuiper Belt in the case of the Pluto, Makemake and Haumea.

Image of Pluto and its moons.

The New Horizons spaceprobe launched January 2006 will arrive at Pluto in 2015, and will then head deep into the Kuiper belt to fly past some KBOs. Not very much is known about Pluto compared to other bodies in the Solar System. It was discovered in 1930 by Clyde Tombaugh, and was classed as a planet for nearly 80 years, until the IAU demoted it in 2006. Pluto has one large moon (Charon) plus two other small ones. Pluto and Charon are rotationally locked, meaning that an observer on Pluto would always see Charon in the same part of the sky permanently. Pluto also has a wildly eccentric orbit which is inclined from the plane of the Solar System. There is an approximately 20 year period when Pluto’s orbit brings the dwarf planet closer to the Sun than Neptune.

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