Brightest and hottest stars have close, turbulent relationships, study suggets

The brightest and hottest stars in our galaxy tend to have short, violent lives, often drawing gas from each other and frequently merging to form a single star, a new study indicates.

By Denise Chow,?Space.com / July 26, 2012

Artist's impression of a vampire star and its victim.

L. Cal?ada/S.E. de Mink/ESO

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A surprising number of massive stars in our Milky Way galaxy are part of close stellar duos, a new study finds, but most of these companion stars have turbulent relationships ? with one "vampire star" sucking gas from the other, or the two stars violently merging to form a single star.

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Astronomers using the European Southern Observatory's Very Large Telescope in Chile studied massive O-type stars, which are very hot and incredibly bright. These stars, which have surface temperatures of more than 54,000 degrees Fahrenheit (30,000 degrees Celsius) live short, violent lives, but they play key roles in the evolution of galaxies.

The researchers discovered that more than 70 percent of these massive stars have close companions, making up so-called binary systems in which two stars orbit each other.

While this percentage is far more than was previously expected, the astronomers were more surprised to find that majority of these stellar pairs have tumultuous relationships with one another, said study co-author Selma de Mink, of the Space Telescope Science Institute in Baltimore.

"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]

Studying stellar behemoths

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.

Source: http://rss.csmonitor.com/~r/feeds/science/~3/IEVgZWttwF8/Brightest-and-hottest-stars-have-close-turbulent-relationships-study-suggets

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