Chapter 23, Problem 1RQ

Why didn’t ancient astronomers know of Uranus’s existence?

To determine

The reason that the existence of Uranus was not known to ancient astronomers.

Answer to Problem 1RQ

The ancient astronomers thought Uranus as just a background star as it is too small and too far from the Earth that its movement is difficult to notice.

Explanation of Solution

Uranus was discovered in $1781$ by William Herschel. It rotates around the Sun in an orbit with radius nearly $20\text{AU}$ and takes $84\text{years}$ to complete one revolution.

Uranus is too small and too far from the Earth that it is difficult to notice it without a telescope.

Its larger time period shows that it moves very slowly around the Sun; therefore, ancient astronomers thought it as just another background star.