In the latest move of an ongoing battle, members of the International Astronomical Union (IAU) voted in Prague today to strip Pluto of its status as the ninth planet in our solar system.
Under the definition adopted today, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune, and Uranus keep their long-held status as official planets.
Pluto, which was declared a planet in 1930, is newly reclassified as a “dwarf planet,” a classification expected to eventually include dozens of other similar objects.
The IAU . . . resolves that “planets” and other bodies in our Solar System be defined into three distinct categories in the following way:
(1) A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass . . . so that it assumes a . . . nearly round . . . shape, and (c) has cleared the neighbourhood around its orbit.
(2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass . . . so that it assumes a . . . nearly round . . . shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects except satellites orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.
In an interview with Space.com, Dr. S. Alan Stern, Executive Director of the Space Science and Engineering Division of Southwest Research Institute, said of the decision, “I’m embarrassed for astronomy.”
Stern is the Principal Investigator for NASA’s “New Horizons” mission to Pluto. The robotic spacecraft launched in January and is expected to arrive at the dwarf planet in July of 2015.
The controversial vote occurred on the last day of the IAU’s 12-day General Assembly meeting, after many voting members had already departed. “Less than 5 percent of the world’s astronomers voted,” said Stern.
“It’s a sloppy definition. It’s bad science,” Stern said in a separate interview with the Associated Press. “It ain’t over.”