Question

A binary star system is observed spectroscopically. Absorption lines from the stars' atmospheres are seen to be Doppler shifted due to the line-of-sight motion of the stars. The stars take turns eclipsing one another at regular intervals. The system's center of mass has a significant velocity relative to the Forth. Which of the following could be true?

A. Both of the absorption lines are red-shifted
B. Both of the absorption lines are blue-shifted
C. One line is red-shifted and one line is blue-shifted
D. The system is seen face-on

Answer 1

In a binary star system, one absorption line is red-shifted and the other is blue-shifted due to the motion of the stars and the system's center of mass. Therefore, option C is correct.

Step-by-step explanation:

The observed Doppler shifts in the absorption lines of a binary star system can provide information about the motion of the stars and the system's center of mass. When one star is moving towards us, its absorption line is blue-shifted, while the other star's absorption line is red-shifted as it moves away from us. If the stars take turns eclipsing one another at regular intervals, it means they have different orbital speeds. Therefore, the correct answer is option C, where one line is red-shifted and one line is blue-shifted.