Most very bright stars have companions
Interaction with binary partners affects the life and death of the heaviest stars.

http://www.physicstoday.org/daily_ed...ave_companions

With masses at least 15 times that of the Sun, type-O stars are the heaviest and brightest of all. And because they live only a few million years, they're quite rare. Having analyzed the O-star populations of six nearby star clusters, a team led by Hugues Sana (Amsterdam University) has concluded that over 70% of O stars—far more than had been thought—have binary companions close enough to exchange matter with them.

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-Sam Wormley