Science Channel Astronomer: "Round Means Planet".. Aug 14, 2006 20:06:58 GMT -6
Post by Chicago Astronomer Joe on Aug 14, 2006 20:06:58 GMT -6
If it's round, it's a planet
Here is a segment from a yahoo group (All astronomy all the time)that was discussing the Pluto debate.
I saw a presentation on the Science Channel about the
debocle. I kind of agree with one of the Astronomers,
but I'd add an addendum to his definition of planet.
Don't remember his name, he's the one who worked with
Dr. Luu and discovered the 1st Kuiper object a few
He said if it's round, it's a planet. That is, if
it's big enough for it's gravity to affect the shape,
it's a planet. He felt the definition should be a
I'd just add the criteria that it goes around the sun.
That is, in can be round, but if orbiting another
solar object then it is not a planet, but a satellite
of the larger object.
I don't see the big issue about whether Pluto is a
planet. That issue was resolved years ago when the
asteroids were discovered. The first few of those
were considered planets till it was realized they are
generally too small to even be round. Then they were
classified as minor planets, or asteroids.
Seems to me that what's missing is not a planet
definition, but a similar concept on moons of planets.
We have nothing in the name to tell us a moon is big
enough (round) to be a planet, or too small
(irregular). Maybe we need "major moons" (planet
sized) and "minor moons" (asteroid sized).
Then it seems the nomenclature would be clear. A
planet orbits the sun and is round. A minor planet
orbits the sun, and is irregular shaped (too small to
be round). A major moon orbits a planet and is round,
and a minor moon orbits a planet and is too small to
be round. In either case, a moon doesn't directly
orbit the sun, but another object that orbits the sun.
It reflects my own personal feeling as stated before in another thread here. If it's round, has an atmosphere and orbits the Sun... it's a planet.