"We already knew that massive stars are very often in binaries," de Mink told SPACE.com. "What is very surprising to us is that they're so close, and such a large fraction is interacting. If a star has a companion so close next to it, it will have a very different evolutionary path. Before, this was very complicated for us to model, so we were hoping it was a minority of stars. But, if 70 percent of massive stars are behaving like this, we really need to change how we view these stars." [Top 10 Star Mysteries]
Type O stars drive galaxy evolution, but these stellar giants can also exhibit extreme behavior, garnering the nickname "vampire stars" for the way they suck matter from neighboring companions.
"These stars are absolute behemoths," study lead author Hugues Sana, of the University of Amsterdam in the Netherlands, said in a statement. "They have 15 or more times the mass of our sun and can be up to a million times brighter."
These massive stars typically end their lives in violent explosions, such as core-collapse supernovas or gamma-ray bursts, which are so luminous they can be observed throughout most of the universe.
For the new study, the astronomers analyzed the light coming from 71 O-type stars — a mix of single and binary stars — in six different star clusters, all located roughly 6,000 light-years away.