Binaries can be very close, sometimes so close that they actually touch each other. Other pairs are extremely wide, with separations up to a light-year or so. Astronomers have known about such wide pairs for a long time, but how they form has been a mystery. The problem is that the typical cloud cores out of which stars are born are not large enough to form the widest binaries.
Continue reading Wide Binary Stars: Long-Distance Stellar Relationships.