December 20, 2012


Star light, star bright: cosmos reveal secret of aging well


Hamilton, Ont. December 20, 2012How do you look great when you’re billions of years old?  A team of international researchers has unlocked some secrets of the cosmos, suggesting our galaxy’s most ancient stars are still young at heart.


Using the Hubble SpaceTelescope, astronomers gathered data from globular clusters formed in the Milky Way some 12 to 13 billion years ago.  The results are published in the latest edition of the journal Nature.


Astronomers set out to determine whether some of the clusters, which are spherical collections of stars tightly bound to one another by gravity, might be aging faster or slower than others.


By studying the distribution of a type of blue star that exists within the cluster, researchers found that some had indeed evolved much faster over their lifetimes.


“Bright, high-mass stars burn up their fuel very quickly, and globular clusters are very old, so there should only be low-mass stars within them,” explains Alison Sills, professor of Physics & Astronomy at McMaster University and a member of the research team. “But that was not the case.”


Stars can be given a new burst of life, receiving extra fuel that bulks them up and substantially brightens them, she says.  This can happen if one star pulls matter off a neighbour, when two neighbouring stars merge together, or if they collide.


The reinvigorated stars are the blue stragglers and their high mass and brightness lie at the heart of the study.


The research, led by Francesco Ferraro at the University of Bologna, suggests that the position of the blue stragglers determines how the stars age.  That is, if the blue straggler stars were distributed evenly throughout, the cluster appeared young.  If they were clumped in the centre, the cluster appeared old.


“It's very exciting to finally be able to use these rare stars, to teach us about the history of an entire star clusters,” says Sills, who is an expert on calculating models of blue stragglers.


“We've thought for years that we should be able to do this, but it wasn't until we had collected years of Hubble Space Telescope and ground-based data that we could finally see this dynamical evolution clearly.”


The international team included researchers from the University of Bologna, University of Virginia, the European Southern Observatory, Pennsylvania State University, McMaster University, among others.



For additional information on the study, please visit:

Photos of Hubble can be downloaded at: 

High resolution photos of Alison Sills can be found at




For more information, please contact:


Alison Sills
Professor, Department of Physics & Astronomy
McMaster University


Michelle Donovan
Public Relations Manager
McMaster University
905-525-9140 ext. 22869