Yes Virginia, Pluto is a Planet
What is a planet? For generations the answer was easy -- A big ball of rock or gas that orbited the Sun. And there were nine of them in our Solar System. But then astronomers started finding more Pluto-sized objects orbiting beyond Neptune. Then they found Jupiter-sized objects circling distant stars. First by the handful and then by the hundreds. Suddenly the answer wasn't so easy. Were all these newly found things planets?
The International Astronomical Union (IAU), who is in charge of naming newly discovered worlds, tackled the question at their 2006 meeting. They tried to come up with a definition of a planet that everyone could agree on. But the astronomers couldn't agree, so they voted and picked a definition that they thought would work. The results have been mixed. In the end, the IAU did accomplish one thing -- They figured out a way to turn something simple into something complex.
The current, official IAU definition says that 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 (Whatever that means).
But this definition baffled the public and classrooms around the country. For one thing, it only applied to planets in our Solar System. What about all those Exoplanets orbiting other stars? They don't orbit the Sun, so are they planets?
And Pluto was booted from the planet club and called a dwarf planet. Is a dwarf planet a small planet? Not according to the IAU. Even though a dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster, a dwarf planet is not just a little planet. In fact, according to the IAU it is not a planet at all.
Eight years later, the Harvard-Smithsonian Center for Astrophysics (CfA) decided to revisit the question of "what is a planet?" On September 18, 2014, the CfA hosted a debate among three leading experts in planetary science, each of whom presented their case as to what a planet is or isn't. The goal was to find a definition that the eager public audience could agree on.
Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU's viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the Exoplanet scientist's viewpoint.
Gingerich argued that "a planet is a culturally defined word that changes over time," and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as "the smallest spherical lump of matter that formed around stars or stellar remnants," which means Pluto is a planet.
After these experts made their best case, the audience got to vote on what a planet is or isn't and whether Pluto is in or out. The results are in, with no hanging chads in sight.
According to the audience, Sasselov's definition won the day, and Pluto is a planet.
Pluto may be a little planet, but it is a planet nonetheless.
For more information:
http://www.cfa.harvard.edu/news/2014-25
http://astro.berkeley.edu/~basri/defineplanet/
http://www.astromart.com/news/news.asp?news_id=568
http://www.astromart.com/news/news.asp?news_id=560
http://www.astromart.com/news/news.asp?news_id=857
http://www.astromart.com/news/news.asp?news_id=719
http://www.astromart.com/news/news.asp?news_id=650
http://www.astromart.com/news/news.asp?news_id=916
AstroMart News Archive:
http://www.astromart.com/news/search.asp?search=.+
The International Astronomical Union (IAU), who is in charge of naming newly discovered worlds, tackled the question at their 2006 meeting. They tried to come up with a definition of a planet that everyone could agree on. But the astronomers couldn't agree, so they voted and picked a definition that they thought would work. The results have been mixed. In the end, the IAU did accomplish one thing -- They figured out a way to turn something simple into something complex.
The current, official IAU definition says that 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 (Whatever that means).
But this definition baffled the public and classrooms around the country. For one thing, it only applied to planets in our Solar System. What about all those Exoplanets orbiting other stars? They don't orbit the Sun, so are they planets?
And Pluto was booted from the planet club and called a dwarf planet. Is a dwarf planet a small planet? Not according to the IAU. Even though a dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster, a dwarf planet is not just a little planet. In fact, according to the IAU it is not a planet at all.
Eight years later, the Harvard-Smithsonian Center for Astrophysics (CfA) decided to revisit the question of "what is a planet?" On September 18, 2014, the CfA hosted a debate among three leading experts in planetary science, each of whom presented their case as to what a planet is or isn't. The goal was to find a definition that the eager public audience could agree on.
Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU's viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the Exoplanet scientist's viewpoint.
Gingerich argued that "a planet is a culturally defined word that changes over time," and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as "the smallest spherical lump of matter that formed around stars or stellar remnants," which means Pluto is a planet.
After these experts made their best case, the audience got to vote on what a planet is or isn't and whether Pluto is in or out. The results are in, with no hanging chads in sight.
According to the audience, Sasselov's definition won the day, and Pluto is a planet.
Pluto may be a little planet, but it is a planet nonetheless.
For more information:
http://www.cfa.harvard.edu/news/2014-25
http://astro.berkeley.edu/~basri/defineplanet/
http://www.astromart.com/news/news.asp?news_id=568
http://www.astromart.com/news/news.asp?news_id=560
http://www.astromart.com/news/news.asp?news_id=857
http://www.astromart.com/news/news.asp?news_id=719
http://www.astromart.com/news/news.asp?news_id=650
http://www.astromart.com/news/news.asp?news_id=916
AstroMart News Archive:
http://www.astromart.com/news/search.asp?search=.+
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