Tonight, your telescope shows you RXJ1800, a galaxy, very near in the sky to the bright star Vega. What can you conclude from this observation?
A)Vega orbits the center of mass of RXJ1800.
B)RXJ1800 and Vega will drift apart from each other on the sky, over a matter of nights.
C)RXJ1800 and Vega will set in the west, at very similar times.
D)Vega and RXJ1800 must be very close to each other, less than a few light years.

Question

Quizplus · Accepted Answer

The fact that RXJ1800 and Vega set in the west at very similar times suggests that they are simply close in the sky, or have a similar declination. It does not necessarily indicate any physical relationship between the two objects, such as orbital motion or proximity.

Tonight, Your Telescope Shows You RXJ1800, a Galaxy, Very near in the Sky