What exactly is the definition of a planet? I've heard lots of talk on if Pluto is or isn't a planet but I don't really know what constitutes a planet?
Sedna eh? Andes backwards, or undies if you prefer.
I don't know if it should be classified as a planet, it's even smaller than Pluto, and both Pluto and Sedna are smaller than our moon, which is 3476km in diameter. And to put things further in perspective the continent of Africa is larger than the circumference of the moon.
All the sub-categories for planet classes are confusing but isn’t the main difference between a ‘star’ which could be a planet nursery or planet eater as follows. “Star” defined as a self luminous object composed of gas with fusion occurring at its core. ‘Planet’ (of any size) larger than an asteroid but smaller than a star. Composed of a fusion-less solid core though not necessarily solidly formed to the planets exterior surface which may be composed of gaseous layers and capable of reflecting light yet not self-luminous? Planets always in orbit to stars?
The definition of 'planet' has been getting murky for a few years now since we now can see further out into the area beyond Pluto and also resolve the many small bodies that are bigger than asteroids and have independent orbits. Once we look at the icy bodies in the outer reaches of the system you'll find probably millions of iceballs like Sedna orbiting the sun. The more we learn, the less our old labels apply. At some point the arbiters of astronomical naming conventions will have to set defining lines, but they don't exist just yet.
I fear we don't have enough letters in the alphabet to give names to all the 'planets' we'll find once we can see well into the Oort cloud. "News flash: 457 new planets discovered today, down 32 from yesterday. Astronomers believe this spring should bring an increase by 25% per day as a new lunar 25 meter observatory goes online..."
Yeah, if we call Sedna a planet, then we gotta call all the objects in the Oort cloud planets just to be fair. As fun as it would be to have a planet for every person on Earth (and then some), I don't think we can't let that happen. Pluto gets grandfathered into planet status due to our prior myopic ignorance, but that's it. From now on, in order of decsending size, I propose they should be known as:
Quasi-Planet Meta-Planet Planetoid Planetisimal Planetoidisimal Near-Asteroid Asteroidette Space Mountain (Pending Disney's willingness to relinquish its trademark for the purpose.) Space Foothill Space Boulder Space Rock Space Pebble Space Speck
Similarly, if we happen to find a planet in our solar system that is larger than Jupiter, I think we should call it a HyperPlanet.
O/T: Is it true that the Internation Astronomical Union has decided to changed the name of Uranus just so we don't have to listen to all the stupid jokes regarding its name? I think I read somewhere that they were planning on calling it Urectum.
(Apologies to Matt Groening and the writers of Futurama.)