Pluto a Planet? New Research from UCF Suggests Yes
The reason Pluto lost its planet status is not valid, according to new research from the University of Central Florida in Orlando. In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet that required it to "clear" its orbit, or in other words, be the largest gravitational force in its orbit. [...] [Philip] Metzger, who is lead author on the study, reviewed scientific literature from the past 200 years and found only one publication -- from 1802 -- that used the clearing-orbit requirement to classify planets, and it was based on since-disproven reasoning.
[...] The planetary scientist said that the literature review showed that the real division between planets and other celestial bodies, such as asteroids, occurred in the early 1950s when Gerard Kuiper published a paper that made the distinction based on how they were formed. However, even this reason is no longer considered a factor that determines if a celestial body is a planet, Metzger said.
[...] Instead, Metzger recommends classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape. "And that's not just an arbitrary definition, Metzger said. "It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body." Pluto, for instance, has an underground ocean, a multilayer atmosphere, organic compounds, evidence of ancient lakes and multiple moons, he said. "It's more dynamic and alive than Mars," Metzger said. "The only planet that has more complex geology is the Earth."
Planet Ceres, please.
The Reclassification of Asteroids from Planets to Non-Planets (DOI: 10.1016/j.icarus.2018.08.026) (DX)
Related: Pluto May Regain Status as Planet
Earth is a "Dwarf Planet" Because it has not Cleared its Orbit
(Score: 2) by unauthorized on Sunday September 09 2018, @07:45AM (1 child)
Yes you can. The rational system is "this arbitrary set of 9 objects are the planets". It was always an arbitrary distinction and we didn't need a precise one because you can't conceivably group Jupiter with Earth in any logical system.
There is no rational basis for having Jupiter be a "planet" but the Sun being a non-planet given the fact that each differs from inner system planets as much as the others in their properties. The nature of the orbit is a really stupid criteria because then you get the mind-bogging stupidity of exo-stellar planets not be considered planets even through they could have once been planets before being ejected from their orbit.
(Score: 1) by khallow on Sunday September 09 2018, @12:37PM
My take is that this is the folly of using complex definitions on the basis of a single instance. It makes no sense to set up such a definition when you don't understand how such systems can vary nor observe them well enough to readily confirm the definition.