Eight years after being reduced to a "dwarf planet" by the International Astronomical Union in 2006, our far distant cousin is finally getting some real push to be upgraded back to the ninth "planet" in our solar system.
The Harvard-Smithsonian Center for Astrophysics, one of the largest astrophysical institutions in the world, recently held a public debate with three major space authorities, including the former chair of the IAU's planet definition committee, Dr. Owen Gingerich. At the end of the debate, the audience voted to reinstate Pluto as a planet.
The current, official definition of a planet, made by the IAU is a celestial body that:
1. is in orbit around the Sun,
2. has sufficient mass to assume hydrostatic equilibrium (a round shape)
3. has "cleared the neighborhood" around its orbit.
If a non-satellite object meets two of these definitions, it may be classified as a dwarf planet. Though that category is not a subsection of planets. According to the IAU, a dwarf planet is as related to a planet as an asteroid is -- not at all. This hard definition has been drawing criticism since the IAU demoted Pluto in a 9-8 vote in 2006.
Gingerich, despite being the former head of the same committee that voted on Pluto's demotion, argued that Pluto was in fact a planet at the Harvard-Smithsonian debate.
According to the Harvard-Smithsonian news blog, "Even though a dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster."
While the decision made by the Harvard-Smithsonian is not the official word on planet classification, it could be a major step toward reopening the planet discussion and challenging the IAU ruling.
The decision to reinstate Pluto as a planet is not a recent topic of debate, however. There has been much argument over the classification of a planet since the ruling was made by the IAU.
Alan Stern, the principal investigator for NASA's New Horizon probe mission to Pluto, famously derided the IAU's decision in 2006, citing the fact that less than 5 percent of all astronomers were included on the vote. His argument contended that because Earth, Mars, Jupiter and Neptune all share their orbits with asteroids, they also do not really meet the true definition of a planet according to the IAU, leaving the rules up for interpretation.
Do you think we should reopen the debate on Pluto? Let us know in the comments below.
Pluto may become a planet again! "A dwarf hamster is still a small hamster," says Harvard-Smithsonian
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In 2005, this image from NASA's Hubble Space Telescope was used to identify two new moons orbiting Pluto (Nix and Hydra), to the right of Charon.