which of the following can help astronomers detect if a star is part of a binary star system

A. the star varies temperatures near the binary star
B. the star wobbles near the binary star
C. the star has very strong gravity
D. the star belongs to an open cluster
Please help I tried the answer but couldn't get it

5 answers

I tried to get the answer sorry
Please help
B is the only "can Help" astronomers, but it is very poor method. Most can't be detected this way. I am surprised your teacher even brought it up.
There are 4 main methods:

Visual detection. Look at the star using your naked eyes or a telescope, and see if it’s a binary. Needless to say, this is the oldest and simplest method.
Detecting eclipses. If the geometry is just right, one star may pass in front of the other once per orbit. This changes the apparent brightness of the star in a periodic way, and detecting these eclipses reveals the existence of a binary.
Spectroscopy. By breaking up the starlight into a rainbow, astronomers can detect absorption lines, corresponding to different elements in the star’s atmosphere. As the star orbits the binary system barycenter, it alternately moves towards and away from Earth. This movement changes the position of the absorption lines, in the same way that an ambulance’s motion changes the frequency of the sound coming from the siren. If the lines’ positions change with a regular period, that indicates a binary system.
Astrometry. You look at the star and see if it moves in the sky. If it does, it could be due to the gravity of its companion star. These motions are very small and hard to detect, so very few binaries have been identified this way. Some might call this wobbling.
Thank you
Thank you for the explanation I really needed it!
thanks alot i really needed a answer