Pluto is no longer in the club of planets, but downgraded to a dwarf planet and a plutonian object.
The voting in the 2006 International Astronomical Union (IAU) General Assembly last Thursday nailed the fate of our remote icy neighbor.
Reluctant Pluto-supporters asked people to “honk if Pluto is a planet”. Anyhow, textbooks now need to be swiftly revised for this coming academic year.
The new criteria of planet are:
1. Orbiting a star,
2. Having enough gravitational force to make itself into a sphere, and
3. Having cleared away objects of comparable size from its orbit.
Pluto, discovered by Clyde Tombaugh in 1930, failed to fulfill the last criteria and was downgraded to be a dwarf planet.
It is joined by Charon, its previous moon, and become the first double planet in the solar system.
One of the main worries for accepting Pluto is its neighbors. “Pluto has too many friends”, said an astronomer.
UB313, nicknamed Xena, was discovered three years ago. It’s a planet further away from the sun but a little bit bigger than Pluto.
Scientists worried that if they let in Pluto, then Xena and other small rubbles would also join the party.
According to the new definition, our solar system consists of eight planets and four dwarf planets: Ceres, between Mars and Jupiter, double planets Pluto and Charon, and UB313 (Xena).
