What's in a name? A lot if that name happens to be the word "planet."

It's a word whose exact definition astronomers and astrophysicists can't seem to agree upon.

It was because of this argument over the definition of the word planet that Pluto was demoted from the ninth planet in the solar system to being just another "dwarf planet" in 2006.

Like Us on Facebook

The debate over that contentious word "planet" has again reignited. And if astronomers and other space scientists can finally agree on a unanimous definition, there's a chance Pluto might again become famous as the ninth planet in our solar system and not just as Mickey Mouse's lovable dog.

The question of when is a planet a planet gained traction following many discoveries of exoplanets in other solar systems.

The question bothering astronomers is whether their definition of the word "planet" should apply only to our solar system, or should it apply to exoplanets, as well. And if applied to exoplanets--many of which are dwarf planets like Pluto--shouldn't Pluto now be called a planet?

Just recently, the Harvard-Smithsonian Center for Astrophysics decided to again revisit the question of "What is a planet?" It hosted a debate involving three leading experts in planetary science.

Those who presented their case as to what is or what isn't a planet were science historian Dr. Owen Gingerich who presented the historical viewpoint; Dr. Gareth Williams, associate director of the Minor Planet Center who presented the viewpoint of the International Astronomical Union (IASU) and Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, who explained the definition of a planet in the light of the discovery of an incredible variety of exoplanets.

The IAU definition says a planet is a celestial body that is in orbit around the Sun; is round or nearly round and has "cleared the neighborhood" around its orbit.

Dr. Gingerich argued that the circumstances surrounding discovery of Pluto were flawed. He also noted that Pluto's orbit isn't planet like and that in a very un-planet-like fashion, Pluto's mass seems to have shrunk over the years.

Despite this, Dr. Gingerich contends Pluto is a planet since "a planet is a culturally defined word that changes over time."

Dr. Williams said Pluto isn't a planet based on the IAU definition's three criteria. He also made the admission that before 2006, when the IAU demoted Pluto to a dwarf planet, the IAU didn't have a definition of a planet.

There wasn't a need to define a planet before the Pluto brouhaha, said Dr. Williams. Coming to a definition of a planet meant the IAU had to form a Planet Definition Committee that defined what a planet is and isn't.

Dr. Sasselov said Pluto is a planet. He considered his definition of a planet according to the big picture of universe.

He noted that the discovery of exoplanets also revealed a variety of planets. Among these strange planets are "free floaters" or planets that don't orbit a star, Super Earths and binary planets.

He did define a planet as the smallest spherical lump of matter that formed around stars or stellar remnants.

After his scientific explanation, Dr. Sasselov quipped "I don't have a clue what a planet is" to much laughter from the audience.

This being the case, he said "my suggestion is let's keep Pluto a planet until we sort this out."

Asked to vote on the question, the audience voted that Pluto is a planet.