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SCIENTISTS agreed at the International Astronomical Union General Assembly in the Czech capital Prague on Thursday that Pluto, which has been called a planet since its discovery in 1930, would be put into a category of planets called ‘dwarf planets’.
Here are some details:
A NEW DEFINITION:
— The meeting agreed that to be called a planet, a celestial body must be in orbit around a star while not itself being a star.
— It also must be large enough in mass for its own gravity to pull it into a nearly spherical shape and have cleared the neighbourhood around its orbit.
— The new definition — the first time the IAU has tried to define scientifically what a planet is — means a second category of planets called “dwarf planets”, has been created. It also creates a third category known as trans-Neptunian objects.
— There are now only eight classical planets, dwarf planets falling into a lesser category and are not considered classical planets along with Mercury, Earth, Jupiter, Saturn, Neptune, Venus, Mars and Uranus.
WHY CHANGE?
— The need to define what it takes to be a planet was driven by technological advances that enable astronomers to look further into space and to measure more precisely the size of celestial bodies in our solar system.
THE RESULTS: IS PLUTO A PLANET?
— Pluto is automatically disqualified as a planet because its oblong orbit overlaps with Neptune’s. Pluto falls into the newly created category called trans-Neptunian objects, which are distinguished from classical planets in that they take longer than 200 years to orbit the sun.
— Pluto would be joined in this new category by two other celestial bodies, Xena and Charon, while another, Ceres, would be known as a “dwarf planet”, though it is not a trans-Neptunian object.—Reuters
