User blog comment:CMDR TRUE LUMINUS/Amazing Sight/@comment-1903369-20170907083020/@comment-34004391-20180117095233

Contact binaries exists, like W Ursae Majoris or VFTS 352.

Sometimes they are merging. Actually KIC 98322227 is calculcated to merge in 2022. V1309 Scorpii did exactly that in 2008, producing a "luminous red nova".

I have seen few systems like this one. Those stars are still inside their roche lobe, or so that their own gravitational force is greater than its neighbour. A beautiful sight.

IIRC, Frontier: Elite 2 had one of these kind of systems (a semidetached binary?) and entering it would crash the game. I guess the math was too complex, and Braben forgot to remove it from the game.