Violent Stars Live With Vampires

Even stars don't want to live alone. A new study shows that most of the bright, high mass stars known as O-type stars in our galaxy usually have partners. What's more, is that these pairs often interact with each other in intimate, and somewhat disturbing ways.

The really strange part is that 75 percent of these stars have another, smaller, 'vampire' star to keep them company. These smaller stars have been found to steal mass from the bigger O-type star. In one-third of these O-type star and vampire star relationships, the stars are actually expected to merge.

O-type stars are stars with immense brightness and a much larger mass than the sun. They live short, volatile lives, and are a major driving force in the evolution of galaxies.

"These stars are absolute behemoths," says lead author of the study Hugues Sana from the University of Amsterdam, Netherlands. "They have 15 or more times the mass of our Sun and can be up to a million times brighter. These stars are so hot that they shine with a brilliant blue-white light and have surface temperatures over 30 000 degrees Celsius."

The team used the European Southern Observatory's Very Large Telescope to observe these stars.

"The life of a star is greatly affected if it exists alongside another star," says Selma de Mink, a co-author of the study. "If two stars orbit very close to each other they may eventually merge. But even if they don't, one star will often pull matter off the surface of its neighbour."

O-type stars have a huge impact on their surroundings due to their short, violent life spans. They can affect the formation of other stars with their wind and solar shocks, as well as spread crucial elements throughout the galaxy with their supernovae. 

The findings will help scientists understand galaxies better.

"The only information astronomers have on distant galaxies is from the light that reaches our telescopes. Without making assumptions about what is responsible for this light we cannot draw conclusions about the galaxy, such as how massive or how young it is. This study shows that the frequent assumption that most stars are single can lead to the wrong conclusions," concludes Hugues Sana.