Like celebrities who never travel without a companion, the brightest stars in the universe generally have their own companion: a second star that orbits close by. At least three-quarters of these extremely bright, exceptionally hot stars have such companions, according to the first survey of so-called O-type stars.
An estimated 20% to 30% of the binary pairs will eventually merge, astronomers reported Thursday in the journal Science, and as many as another 50% of the O-type stars will have much of their hydrogen stripped away by their companions, which are commonly called vampire stars.
O-type stars account for less than 1% of the stars in the universe, but they are the brightest and heaviest. With a mass at least 15 times that of our own sun and surface temperatures exceeding 30,000 degrees Celsius, they shine a brilliant pale blue and are as much as a million times brighter than the sun. Although they are rare, they have a disproportionate effect on their surroundings. The winds and shocks coming from them can both trigger and stop star formation, their radiation powers the glow of bright nebulae, their supernovae enrich galaxies with the heavy elements crucial for life, and they are associated with gamma-ray bursts, which are among the most energetic phenomena in the universe. They are thus associated with many of the mechanisms that drive the evolution of galaxies,