Question

Why do some astronomers object to the new definition of a planet that was adopted in 2006?

A. New space missions show that Pluto is much larger than originally thought.

B. By this definition, Earth, Jupiter, and other planets should not be considered planets.

C. There was never a vote on whether to adopt the new definition or not.

D. It means that we now technically have over 100 planets.

Answer 1

Answer: B. By this definition, Earth, Jupiter, and other planets should not be considered planets.

Because, It defined a planet as orbiting a star, which would have meant that any planet ejected from its star system or formed outside of one (a rogue planet) could not have been called a planet, even if it fit all other criteria. However, a similar situation already applies to the term 'moon'—such bodies ceasing to be moons on being ejected from planetary orbit—and this usage has widespread acceptance. Another criticism was that the definition did not differentiate between planets and brown dwarf stars. Any attempt to clarify this differentiation was to be left until a later date.