Before the discoveries of the early 21st century, astronomers had no real need n's orbital period, astronomers could accurately calculate Pluto's mass for the first time, which they found to be much smaller than expected.
Before the discoveries of the early 21st century, astronomers had no real need for a formal definition for planets. By measuring Charon's orbital period, astronomers could accurately calculate Pluto's mass for the first time, which they found to be much smaller than expected.