If astronomers measure the parallax of a star against the background stars and conclude that the star has a parallax of 0.004 arcsec, how far is the star from Earth?
A) 25 pc or 81.5 ly
B) 250 pc or 815 ly
C) 400 pc or 1300 ly
D) 0.004 pc or 0.013 ly

Question

Quizplus · Accepted Answer

The distance to a star in parsecs is the inverse of its parallax angle in arcseconds. Therefore, 1/0.004 arcsec = 250 parsecs.

If Astronomers Measure the Parallax of a Star Against the Background