A surprising fact about the Universe is that a significant number of stars are in binary systems , where two stars orbit each other. It depends on the type of star — red dwarfs tend to be more solitary, while high-mass stars are more likely to be in multiple systems — but something like 1/3 of all stars are in binary systems.  As an example, if you pick 100 stars in the sky, roughly 70 will be solo, like the Sun, and 30 will be in binaries — 15 binary systems. There’s also a chance some will be in higher-order systems, like trinaries or quatenaries or even more stars all orbiting each other. But… why? We have a pretty decent understanding of how stars form in general, but are there specific conditions that make it more likely for stars to form close enough together to become gravitationally coupled? And if so, what are they? This isn’t well understood at all. So, to help clear it up, a team of astronomers looked to Orion.…