Is Pluto the Only Dwarf Planet?

In August 2006, members of the International Astronomical Union (IAU) voted to demote Pluto to the status of a dwarf planet. Planets of this type are celestial bodies that are in regular orbit around a sun and have sufficient mass to be shaped by its own gravity but generally are smaller than the planet Mercury. Unlike moons, dwarf planets do not orbit inner or outer planets. Along with Pluto, there are four other known dwarf planets in the solar system: Eris, Makemake, Haumea and Ceres.

More facts about dwarf planets:

  • Ceres and Pluto are relative newcomers to the status of dwarf planet. Ceres was elevated from the status of asteroid or minor planet to dwarf planet in 2006, the same year in which Pluto was demoted.

  • Pluto is tilted on its axis, a factor that affects it orbit. Every 248 Earth years, Pluto slips into the orbit of Neptune and remains within that planet’s orbit for 20 years.

  • Makemake and Haumea were classified as dwarf planets after the reassignment of Pluto. Makemake was accepted as a dwarf planet on 11 July 2008, and Haumea received this classification on 17 September 2008.

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Discussion Comments


No, Pluto and Neptune are highly unlikely to collide. This is due to Pluto's being out of the standard disc shape that planets orbit in. This results in a 3D path where Pluto's distance from the Sun crosses over Neptune's same distance from the Sun at a different 3D point in Space.

There is also synchronisation of their orbits likely due to gravitational forces of Pluto and Neptune. This synchronisation prevents them from being to close. The only reason they would collide is due outside forces giving them a change in orbit, as would be the same for all the discovered planets in our solar system.


I guess that means sometime in the future a collision between pluto and neptune is inevitable.

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