What is the definition of "PLANET"?

Question

There are 53 rounded object in the solar system where 43 "New Planets" were found in Kuiper Belt. So can we call them a planet? Or is there any new definition of planet?

Answer 1

According to the definition recently adopted by the International Astronomical Union (IAU), a planet is a celestial body that [1]:

(a) is in orbit around a star or stellar remnants;
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape;
(c) is not massive enough to initiate thermonuclear fusion of deuterium in its core; and,
(d) has cleared the neighbourhood around its orbit.
Under this definition, the solar system is considered to have eight planets. Bodies which fulfill the first three conditions but not the fourth (such as Pluto and 2003 UB313) are classified as dwarf planets, providing they are not also natural satellites of other planets.

Before the adoption of this definition, there was no scientifically specified definition of "planet", though the solar system had been traditionally enumerated as having various numbers of planets over the years, being seven, eight, twelve and, most recently, nine.

I think its just a matter of naming convention. Its just an object. For example, it doesnt harm to call me Nic or Nicky or Nicholyn as long as you know its still me.

Answer 2

Astronomers at the IAU meeting in Prague cast their votes to define a planet in our solar system as "a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit."

Answer 3

[quote]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."
[/quote]

therefore a few conditions for something to be a planet:
1) orbits the sun, and not another planet (this excludes the moon from ever becoming a planet)
2) big enough to be round
3) big enough to have cleared its orbit of almost all smaller objects

Answer 4

As we found out this past week, a planet has to have its own orbit, separate from another planet. I gather it must be composed of more than ice and rock as well and must be of a certain size. All just a matter of semantics!!!

Answer 5

"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."

Answer 6

I think the original in Greek means "Wandering Star" the rest of the definition we use today has only been used since we have had telescopes.

Answer 7

A planet is, no wait, it changed again....

A planet is a small plan.