org, match astronomers' ideas about what would be left if a blue straggler
took gas from a now-defunct companion star.
To better understand cluster ageing, the team mapped the location of blue straggler
stars in 21 globular clusters, as seen in images from Hubble and the MPG/ESO 2.
Basically, in a mass-transfer scenario, the reason one star ends up as a blue straggler
is that its companion dumps mass on it," says Christian Knigge (Southampton University, England).
The extent of the blue straggler
population detected provides two new constraints for models of the star-formation history of the bulge.
Christopher Frohmaier was nominated for his project Blue Straggler
Stars in the Globular Cluster M30 , which investigated the nature of these unique and enigmatic variety of stars that appear to defy the normal stellar ageing process.
The standard explanation is that a blue straggler
acquired fresh new mass late in life from another star.
Stars "A puzzling feature of many globular clusters is the presence in them of an appreciable number of fairly hot stars, in apparent defiance of the modern theory of stellar evolution.
Many researchers believe the typical blue straggler
arises from two elderly, lower-mass stars that collided and merged to form a massive, hotter star.
A team of astronomers used Hubble to study the blue straggler
star content in Messier 30, which formed 13 billion years ago and was discovered in 1764 by Charles Messier.
That means if a given blue straggler
formed with the rest of its star cluster, it should have died billions of years ago," Knigge said.
The only thing that was clear is that at least two stars must be involved in the creation of every single blue straggler
, because isolated stars this massive simply should not exist in these clusters," said Dr Christian Knigge from Southampton University, who led the study.
The team used the Hubble Space Telescope's Faint Object Spectrograph to obtain the temperature, size, and rotation rate of a blue straggler
in the heart of 47 Tucanae, a globular cluster visible from the Southern Hemisphere.