Massive Stars Found to Orbit a Partner –New Discovery




An international team of researchers from the USA and Europe including from the University of Bonn under the direction of Dr. Hugues Sana at the University of Amsterdam has discovered that the most massive stars in the universe don't spend their lives in space as singles as was previously thought. More than two-thirds orbit a partner star.

"The orbit paths of the stars are very close together so that the region around these stars is turbulent and by far not as calm as previously thought," says Professor Norbert Langer from the University of Bonn. What happens is that one star can suck the material out of its companion like a vampire or both stars can melt to become an even larger massive star.

Astronomers evaluated more than ten years' worth of observations using one of the world's largest telescopes, the Very Large Telescope (VLT) in Chile's Atacama Desert.

*"The spectacular new research findings could only have been gathered based on one of the most extensive observation campaigns in this area," says Professor Robert Izzard. A total of 71 massive stars in six young galactic star clusters were observed for years. Through close-knit monitoring, researchers were able to determine the paths of over three-quarters of the double stars discovered which led to unique precision.

"The current study reveals that the fast majority of all massive stars spend their lives with a partner," states Fabian Schneider, the third scientist based in Bonn. Over time, roughly one-third of the star systems melts with their companion, while the other two-thirds transfer material to its partner.

Massive stars, also called spectral class O stars because of their characteristics are the brightest and the most short-lived stars in the universe. In the beginning they are more than 15 times as massive as our Sun. The end of their life is marked by spectacular supernova explosions or gamma ray bursts. They account for a large part of all the heavy elements in the universe.

"The new insight into the lives of massive stars has a direct impact on the understanding of the final stages most massive stars experience," says Professor Langer. The gigantic explosions at the end of a star's life can be observed from almost all corners of the universe.

One star in the open cluster Pismis 24, shown at the top of the page,  is over 200 times the mass of our Sun, making it a record holder. This star (shown below) is the brightest object located just to the right of the gas front in the above image.

Close inspection of images taken recently with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record.

Toward the image left, stars are still forming in the associated emission nebula NGC 6357, including several that appear to be breaking out and illuminating a spectacular cocoon.  



The Daily Galaxy via and H. Sana et al., Science, July 27, 2012 (DOI 10.1126/science.1223344)

Image credit: NASA, ESA and J. M. Apell├íniz (IAA, Spain)


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