Binary (double) stars can be detected by
a. being seen as two separate stars with a telescope.
b. one star traveling a wiggly proper-motion path across the sky.
c. one star dimming abruptly as another passes in front of it.
d. pairs of absorption lines seen in the spectrum of what appears to be one star.
e. All of the other choices are correct.
Question 2
Which blurs our Earth-based view of celestial objects?
a. the Sun
b. the Moon
c. Earth's atmosphere
