Question

8. Summarize the case for why Pluto should not be considered a planet.

Answer 1

The reason for which Pluto is not considered as planet are as follows:-

1. Pluto is smaller than any other planet -- even smaller than Earth's moon.

2. It's dense and rocky, like the terrestrial planets (Mercury, Venus, Earth and Mars). However, its nearest neighbors are the gaseous Jovianplanets (Jupiter, Saturn, Uranus and Neptune). For this reason, many scientists believe that Pluto originated elsewhere in space and got caught in the sun's gravity. Some astronomers once theorized that Pluto used to be one of Neptune's moons.

3. Pluto's orbit is erratic. The planets in our solar system all orbit the sun in a relatively flat plane. Pluto, however, orbits the sun at a 17-degree angle to this plane. In addition, its orbit is exceptionally elliptical and crosses Neptune's orbit.

4. One of its moons, Charon, is about half Pluto's size. Some astronomers have recommended that the two objects be treated as a binary system rather than a planet and satellite.

5. Pluto does not has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.