What Pluto really is

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"What Pluto really is"
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A planet? A planet not. A planet? A planet not. All these recent hype about what Pluto really is has been the talk of the town ever since the International Astronomical Union (IAU) affirmed its decision on August 24 in stripping Pluto of its planetary status. According to its new rules, a planet should fulfil three criteria which are: a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.

In particular, the third criteria (c) has caused an uproar amongst the astronomers as they argued that not only was it poorly defined, but it was also unable to explain the extent to which a 'neighbourhood' should be cleared before an object can be called a planet.

Dr Alan Stern, who leads the US space agency's New Horizons mission to Pluto and did not vote in Prague, told the BBC News: "It's an awful definition; it's sloppy science and it would never pass peer review." Dr Stern also went on to criticize that "the actual definition is even worse, because it's inconsistent."

While astronomers and the general public are still caught in a heated debate over the planethood of Pluto, Nature remains oblivious. Far out in the outer reaches of the Solar System, Pluto - along with its close relatives like the Plutinos and Twotinos - continues to orbit the Sun in a 3:2 resonance with an eccentricity.

Orbiting at a distance of approximately 39.48 AU from Sol, Pluto is found residing right in the middle of a broader class of rocky objects known as the Kuiper Belt Objects, or KBOs. The Kuiper Belt is an area of the Solar System extending from 30 AU to 50 AU from the Sun. Similar to its counterparts in terms of structure, size, orbit eccentricity as well as distance from the Sun, Pluto makes an excellent fit in the class of Kuiper Belt Objects.

Since Pluto has also been widely recognised as a KBO in the past few decades, its newly designated term as a 'dwarf planet' seems awfully unnecessary. Perhaps, the only question that remains is, "Do we really need another planet in our lonely Solar System that badly?"

More about this author: Lynn Koh

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