This answer discusses contact binaries, which I did not even know existed. I can understand how they could exist for a short time (maybe) as gravitational waves carry off energy that causes the stars’ orbits to slowly decay, but how can they persist? My main concern is that surely the stars orbit within the Roche limit of each other (or at least the smaller one orbits within the Roche limit of the larger one). Has there been any good theoretical work on their stability?
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