Pluto: A Planet?

Pluto: A Planet?

Many issues have arisen from the debate whether or not Pluto is a planet. Some astronomers say that Pluto should be classified as a “minor planet” due to its size, physical characteristics, and other factors. On the other hand, some astronomers defend Pluto’s planet status, citing several key features.
Indeed, most of the problem is that there is no formal definition of a planet. Furthermore, it is very difficult to invent one that would allow the solar system to contain all nine planets. I suggest that for an object to be classified as a planet, it must embody three characteristics. It must be in orbit around a star (thus removing the larger satellites from contention), it must be too small to generate heat by nuclear fusion (so dwarf stars are excluded) and it must be massive enough to have collapsed to a more or less spherical shape (which excludes comets, and most of the asteroids). These criteria would admit a few of the larger asteroids and probably some of the Kuiper belt objects as well, but adding a requirement for a planet to have a minimum diameter of 1,000 km would remove the larger asteroids from contention while retaining Pluto.
Below are some brief reasons as to why Pluto may not be considered a planet with my rebuttal.
Pluto is small compared to the other planets.
Pluto is about half the size of the next smallest planet, Mercury. However, there is no scientific reason whatsoever to pick the size of Mercury as being the size of the smallest object to be called a planet. Mercury itself is less than half the size of Mars, and Mars is only about half the size of Earth or Venus. Earth and Venus are only about one-seventh the size of Jupiter. Why not pick one-tenth the size of Jupiter as the size of the smallest planet, if the cutoff is going to be chosen arbitrarily? In that case, Mars, Mercury and Pluto would all have to be classified as asteroids. If the size-cutoff between asteroids and planets is going to be randomly chosen, the cutoff value should be agreed upon in open debate among interested scientists.

Pluto is smaller than 7 moons in the solar system.
Pluto is smaller than Earth's Moon, Jupiter's moons Io, Europa, Ganymede, and Callisto, Saturn's moon Titan, and Neptune's moon Triton. On the other hand, Pluto is larger than the other 40 known moons in the solar system. There is no scientific reason to arbitrarily dis...

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...Willem J. Luyten
Science, New Series, Vol. 123, No. 3203. (May 18, 1956), pp. 896-897.
Stable URL:
This site is very reliable. It is the Scholarly Journal Archive.

2. Letters
The Planet Pluto
Gerard P. Kuiper
Science, New Series, Vol. 124, No. 3216. (Aug. 17, 1956), p. 322.
Stable URL:
This site is very reliable. It is the Scholarly Journal Archive.

3. Research News
Planetary Scientists are Seeing the Unseeable
Richard A. Kerr
Science, New Series, Vol. 235, No. 4784. (Jan. 2, 1987), pp. 29-31.
Stable URL:
This site is very reliable. It is the Scholarly Journal Archive.

4. This is a site about Pluto. It is reliable since it is a part of an established academic institution.

5. This is the NASA page for Pluto.

6. Another site from NASA.

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