Binary Star Orbits

Hi,
Is it possible for a binary system to exist there one of the stars is travelling in the opposite direction along its orbit, or would this be too unstable and end up with both stars flying off in oposite directions f it were to happen?Cheers,~Al

Al,

Interesting thoughts but in reality, I cannot see how this scenario could happen. Binary stars are subject to Kepler’s Laws and, as you say, have elliptical orbits around their common centre of mass.

In other words, the two stars will always be at opposite ends of a straight line through the centre of mass. This would not be possible if the stars were orbiting in opposite directions.

Gordon

Al

I have to agree with Gordon. In fact, if you consider two stars and a centre of mass, then the centre of mass is only a construct we use to provide a handy frame of reference. So ... if you get rid of the CM, you have one star orbiting another, and the direction is immaterial.

Now if you asked about a system of multiple stars, that would be more interesting!

Owen

I think I understand what you're saying Gordon. Just so as i understand this concept of centre of gravity completely, if you have two stars orbiting each other, the centre of gravity is proportional to their respective mass and distance between them; is that correct?

Now, if you move the stars apart so as to increase their seperation by a factor of two, does the centre of gravity move and by how much? (assuming say, that one star is twice the mass of the other)

Do two objects have to be in orbit about each other for there to be a centre of gravity? Is there a centre of gravity between our Sun and say Proxima Centauri?

Thanks,

Michael