Pluto a Planet Again? Public Says Yes After Astronomy Debate (+Video)

October 1, 2014 Updated: October 2, 2014

Pluto should be defined as a planet again, according to a recent public vote on the issue.

The vote was held after astronomers debated the issue, with other scientists, teachers, and others voting on the issue.

The Harvard-Smithsonian Center for Astrophysics held the debate, with three experts weighing in–two arguing that Pluto should be defined as a planet. 

Dimitar Sasselov, director of Harvard’s Origins of Life Initiative, said that he isn’t ready to pass judgement on what consitutes a planet before deep-space exploration turns up more discoveries.

“Let’s keep Pluto a planet until we sort it out,” Sasselov said, according to a report from Harvard.

He noted that a planet can be defined as “the smallest spherical lump of matter that formed around stars or stellar remnants.”

David Aguilar, the host, noted that only 400 people–the International Astronomical Union–voted in 2006 that Pluto is a dwarf planet, not a planet. 

“The basis of that decision: A number of other worlds have been discovered at the margins of the observable solar system, and Pluto might not even be the largest of these frosted runts. Astronomers suspect there are hundreds more of these worlds waiting to be discovered,” noted National Geographic in summarizing the union’s decision.

“How, then, could Pluto alone be called a planet? The IAU needed to figure out how to classify Pluto and its friends, and describe what made them different from the classical eight planets. So, the assembly voted to call them ‘dwarf planets,’ and Pluto became one of the first entries in the new official category. Joining it are Ceres, in the asteroid belt, and Eris, Haumea, and Makemake, which like Pluto live in the icy Kuiper Belt beyond Neptune’s orbit.”

Members of the International Astronomic Union (IAU), vote on a resolution for planet definition during the IAU 26th General Assembly in Prague, Czech Republic on Aug. 24th 2006. The world's leading astronomers voted on Pluto being newly classified and called as "Dwarf Planet".  (AP Photo/Petr David Josek)
Members of the International Astronomic Union (IAU), vote on a resolution for planet definition during the IAU 26th General Assembly in Prague, Czech Republic on Aug. 24th 2006. The world’s leading astronomers voted on Pluto being newly classified and called as “Dwarf Planet”. (AP Photo/Petr David Josek)

But the debate revisited the argument, with Owen Gingerich, professor emeritus of astronomy and of the history of science at Harvard and a senior astronomer emeritus at the Smithsonian Astrophysical Observatory, referencing how the definitions for heavenly bodies have been shifting for centuries.

“What is a planet is a culturally defined word that has changed over the ages,” Gingerich said. “The IAU was foolhardy to try and define the word planet.”

The sole dissenter on the panel was Gareth Williams, associate director of the Minor Planet Center, who said that “Pluto seemed to shrink over the years,” from about equal the mass of Earth to about 1/459 the mass of Earth.

“In my world, Pluto is not a planet,” he said.

According to Nat Geo, after the arguments, the audience in Cambridge, Massachusetts—a mix of scientists, teachers, and the public–voted on whether Pluto is a planet, or not, and the majority said that it’s a planet.

The specifics of the vote weren’t disclosed.

“Every time there is poll it turns out this way,” planetary scientist Alan Stern told Time magazine.“The IAU have become largely irrelevant on this.”

Follow Zachary on Twitter: @zackstieber
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