According to "When Is a Planet Not a Planet?" scientists determined that Pluto was not a planet. What were the causes that led t
hem to this conclusion? Select three answers. A. Pluto also orbits around another sun. B. Pluto resembles a moon more than a planet. C. Pluto’s orbit crossed over the orbit of another planet. D. Pluto’s orbit is not the same shape as the orbits of the other planets. E. Scientists believed the theory that the outer planets were all made of gas, and Pluto had a rocky core.
The correct answer will be: C. Pluto’s orbit crossed over the orbit of another planet.
Explanation:
When determining whether a planet is planet the IAU stated the planet must (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 hydro-static equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit. For poor Pluto's case he did not clear part (c).
