If an astronaut were to look back from his spacecraft toward the solar system and measure that the angle between Earth and the Sun was 1 arcsecond, how far from the un would the astronaut be? (Assume that the Earth-Sun line is at right angles to your line of sight.)
A) 1 Mpc
B) 1 au
C) 1 pc
D) 1 ly

Question

Quizplus · Accepted Answer

The distance at which an angle of 1 arcsecond is subtended by 1 astronomical unit (the average distance from the Earth to the Sun) is defined as 1 parsec (pc). Therefore, if the angle between Earth and the Sun as seen by the astronaut is 1 arcsecond, the astronaut would be 1 parsec away from the Sun.

If an Astronaut Were to Look Back from His Spacecraft