You observe Neptune as it occults a background star when the relative velocity between Neptune and the Earth is 30 km/s, and the star crosses through the middle of the planet and disappears for 27.6 minutes. What is Neptune's diameter?

Question

Quizplus · Accepted Answer

Neptune's diameter is given by:$$D = v 	imes t$$where:* D is the diameter* v is the relative velocity* t is the time it takes for the star to cross the planetPlugging in the given values, we get:$$D = 30 	ext{ km/s} 	imes 27.6 	ext{ minutes} 	imes 60 	ext{ s/minute} = 4.9 	imes 10^4 	ext{ km}$$Which is closest to choice A.

You Observe Neptune as It Occults a Background Star When