Prague, Aug. 24: Forget what you learnt in school. Pluto is no longer one of the nine planets of the solar system.
Astronomers from around the world ruled today that the much-maligned Pluto, named after the god of the underworld in classical mythology, does not qualify as a planet under historic new guidelines that downsize the solar system to eight planets.
“Pluto is dead,” Mike Brown of the California Institute of Technology bluntly told reporters on a teleconference.
Discovered in 1930 by the American Clyde Tombaugh, Pluto has traditionally been considered the ninth planet, farthest from Sun in the solar system.
However, the definition of a planet approved after a heated debate among 2,500 scientists from the International Astronomical Union (IAU) meeting in Prague drew a clear distinction between Pluto and the other eight planets.
Pluto will now be classified as a “dwarf”.
The new definition (see chart) — the first time the IAU has tried to define scientifically what a planet is — means a second category called “dwarf planets” has been created, as well as a third category for all other objects, except satellites, known as small solar system bodies.
With one vote, toys and models of the solar system became instantly obsolete, forcing teachers and publishers to scramble to update textbooks.
The need to define what is a planet was driven by technological advances enabling astronomers to look further into space.
“It’s an issue mainly for the public, not really for scientists. Some people may be upset, but we’ve long regarded it (Pluto) as a minor planet,” an astronomer said.
The decision at the Prague conference of astronomers from 75 countries was a dramatic shift from just a week ago, when they came up with a new definition that would have saved the tiny Pluto’s place in Sun’s family.
That plan proved highly unpopular, dividing the group into factions and triggering an acrimonious debate full of angry denunciations that ultimately sunk Pluto.
Two of the objects that at one point looked like they might become full-fledged planets will now join Pluto as dwarfs: the asteroid Ceres, which was a planet in the 1800s before it too got demoted, and 2003 UB313, an icy object slightly bigger than Pluto nicknamed Xena, discovered by Brown.
Charon, the largest of Pluto’s three moons, is no longer under consideration for any status at all.