Still a planet to me…
Leading astronomers declared Thursday that Pluto is no longer a planet under historic new guidelines that downsize the solar system from nine planets to eight.After a tumultuous week of clashing over the essence of the cosmos, the International Astronomical Union stripped Pluto of the planetary status it has held since its discovery in 1930. The new definition of what is — and isn’t — a planet fills a centuries-old black hole for scientists who have labored since Copernicus without one.
I much prefered the previous ruling that added new planets to this one. Regardless, I will continue to call Pluto a planet.
Here is the new definition, and why Pluto doesn’t make it:
Much-maligned Pluto doesn’t make the grade under the new rules for a planet: “a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a … nearly round shape, and has cleared the neighborhood around its orbit.”
Pluto is automatically disqualified because its oblong orbit overlaps with Neptune’s.
It is unclear to me why Pluto and Neptune having overlaping obrits would disqualify Pluto but not Neptune.
It seems to me that this defintion is pretty subjective and I expect that it will become useless as we learn more about other planetary systems and find things that really should be planets but haven’t ‘cleared their neighborhood’s.’
Honestly, it never made much sense to me that Pluto was a planet. It doesn’t orbit on the same plane as the other planets, it doesn’t have the same shape orbit as they do, and it’s “moon” or “co-planet” or whatever, is barely much smaller than it is. It’s clearly space junk that got kicked out of whatever orbit it was in.
I think the requirement that a planet clear it’s orbit makes a lot of sense. Clearly, when Pluto and Neptune meet, Neptune is going to win.
Really, though, the concept of “planet” is arbitrary and subjective, no matter how you peel it. I think it should be “Any body that formed as a primary gravity-spherical body out of the original accretion disk of a star.” Anything else needs a qualifier, like “Captured planet” or “Sub-stellar body”. But really, “planet” by itself doesn’t mean anything of value, so how it’s defined really isn’t important.