Astronomers refer to these objects as blue stragglers

Oct 20, 2011 14:32 GMT  ·  By

A group of astronomers at the Northwestern University may have finally figured out why is it that stars called blue straggler appear to be getting younger with time. Usually, these objects are found siphoning matter off their companions, which is why they are also called vampire stars.

One thing that separates these objects from any others is the fact that they appear to be younger than, say, companions in a stellar cluster. That is to say, they tend to burn hotter, and therefore appear bluer on camera than their cooler, redder partners.

Experts have been wandering as to why this happens for many years, but thus far they were unable to discover the correct answers. In the new investigation, the Northwestern team proposes a potential origin for this class of objects.

Some of the possible answers that were taken under consideration over the years included the collision of separate stars, the accretion of matter from companions, or instances when a would-be blue straggler moves through a hydrogen cloud.

“People have been trying to explain the origin of blue stragglers since their discovery in 1953,” Northwestern astronomer and lead study author Aaron Geller explains. In the investigation, he and his team were finally able to conclude that blue stragglers are indeed stellar cannibals.

In order to arrive at this conclusion, the team used the Tucson, Arizona-based WIYN Observatory to investigate the constellation Cepheus. More than 3,000 stars were surveyed in this cluster, which is estimated to be around 7 billion years old.

At the same time, the researchers carried out several computer simulations of the most likely scenarios to explain the origins of blue stragglers. Star mergers and interstellar collisions were eventually ruled out as possible culprits, Space reports.

This means that blue stragglers most likely form by stealing matter from their companions. The study provides critical new insight into stellar formation and evolution, while at the same time “solving the mystery of where these blue stragglers come from,” Geller explains.

“It's really the companion star that helped us determine where the blue straggler comes from. The companion stars orbit at periods of about 1,000 days, and we have evidence that the companions are white dwarfs. Both point directly to an origin from mass transfer,” he goes on to say.

“As so often happens in astronomy, it is the objects that you don't see that provide the critical clues,” adds University of Wisconsin-Madison (UWM) astronomer and study co-author Robert Mathieu.

Details of the new study were published in the October 20 issue of the top scientific journal Nature.