Pluto Is A Planet After All

Not long after scientists decided Pluto didn’t fit the definition of a planet, a new public debate has determined that Pluto is a planet once again.

According to Science Alert, a group of scientists gathered last week to debate over what a planet actually is. After a popular vote, the congregation decided that Pluto does, indeed, fit the description of a planet — at least for the purposes of our solar system. The debate over Pluto’s fate took place at the Harvard-Smithsonian Center for Astrophysics between three experts. After a debate in front of an audience of scientists, teachers and civilians, the three scientists took a vote on Pluto. Two of them voted that Pluto should be a planet and the other voted against.

The initial decision to remove Pluto from the solar system was made in 2006 by the International Astronomical Union (IAU), who determined Pluto was too small to qualify as a planet when compared to the other eight planets in the solar system. Many astronomical objects larger than Pluto have been discovered, like the dwarf planet Eris, that were never considered to be planets. The reasoning was that Pluto shouldn’t count as a planet either if other bigger worlds weren’t earning the classification.

The definition of what a planet is has changed several times in recent history, but the argument put forward by the first scientist in favor of Pluto’s planet-hood had little to do with the official definition. A historian named Owen Gingerich argued that a planet is not determined by astronomical definitions but by human culture. Therefore Pluto must be a planet because humanity decided it was long ago.

Dimitar Sasselov’s argument was much more scientific in nature. Sasselov, the director of Harvard’s planetary program, the Origins of Life Initiative, claimed that a planet is defined as the smallest spherical lump of matter that formed around stars or stellar remnants, meaning Pluto is a planet.

The scientist who argued against Pluto as a planet was Gareth Williams from the IAU’s Minor Planets Center. He argued that a planet is a spherical body that orbits the Sun and has cleared its path, meaning Pluto can’t be a planet.

The Harvard audience voted and overwhelmingly supported Sasselov’s argument in favor of Pluto being called a planet. According to Time, the planetary scientist Alan Stern made the following comment about the Pluto vote:

“[e]very time there’s a poll it turns out this way. The IAU have become largely irrelevant in this.”

Stern is the principal investigator of the New Horizons probe, which will arrive at Pluto next summer, allowing scientists to examine the heavenly body (planet or otherwise) close up for the first time.

What do you think about the Pluto vote? Should Pluto be a planet?

[Image courtesy of NASA]