Type-O Stars Enjoy Togetherness.
Weighing in at fifteen times more mass than the Sun, type O stars might be big – but they’re never lonely. These ultra-brilliant, pale blue suns shine incredibly brightly and burn hot – living short, violent lives. Yet, despite their bad traits, Type O stars have a redeeming feature… about 75% of them have a companion star. Thanks to studies done with ESO’s Very Large Telescope (VLT), researchers are now learning that most of these stellar pairs are sharing… sharing disruptive interactions, as well as mass. In a ring where two stars enter, more often than not, only one star leaves.
“These stars are absolute behemoths,” says Hugues Sana (University of Amsterdam, Netherlands), the lead author of the study published in the July 17 issue of Science. “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.”
In the study, 71 O-type single stars and stars in pairs (binaries) in six nearby young star clusters in the Milky Way were examined by astronomers. By examining them spectroscopically, the researchers were able to determine that a large percentage of this particular star type were part of a binary system. However, their most profound discovery was that most of them were close enough to each other to interact… a finding which causes us to re-think galactic evolution.
“The life of a star is greatly affected if it exists alongside another star,” says Selma de Mink (Space Telescope Science Institute, USA), 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 neighbor.”
While Type O stars comprise only a small portion of the Cosmos, their violent behavior has a huge impact on space around them. The emit strong stellar winds, they light up nebulae, they produce shock waves which can stop star formation and if one goes supernova, it provides a rich environment for growth. Not only are they responsible for all this, but the can also be a source of deadly gamma ray bursts. In short, O-types play a huge role in how a galaxy ages.
So why are these new findings so unusual? Until recently most scientists theorized that closely-orbiting massive binary stars were rare. They were the responsible party for spectacular events such as black hole binaries, x-ray binaries and duo-pulsars. Through this new study, we can’t look at Type O star systems as the simple answer – because they aren’t simple stars.
“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.
Original Story Source: ESO News Release.