AsianScientist (Jun. 3, 2016) – A research team in Australia has made an unexpected discovery that a large group of stars are dying prematurely. Their findings, published in the Monthly Notices of the Royal Astronomical Society, challenge our accepted view of stellar evolution.
Led by Professor John Lattanzio of Monash University, the researchers showed that large numbers of helium-burning stars are dying prematurely in the M4 globular cluster. M4 is one of the closest and brightest globular clusters, and has already been very well studied. Lattanzio described the discovery as a surprising one to find in our very own backyard.
“Globular clusters are some of the oldest objects in the Universe. Although we have some ideas for what is going on in them, every time we look carefully we find something unexpected. They are fascinating and frustrating at the same time,” he said.
The researchers used a new instrument called a high efficiency and resolution multi-element spectrograph (HERMES). With HERMES, the researchers could decipher the starlight of stars in M4 to work out their chemical composition. They found that about half of the stars tend to skip the Red Giant phase, instead becoming White Dwarfs millions of years ahead of schedule.
While the cause of this remains a mystery, the analysis has revealed that premature death tends to only occur in sodium-rich or oxygen-poor stars.
Surprisingly, the best computer models do not predict that these stars will die young.
“Computer simulations do not agree with this observation; so as well as continuing observations, new computer models will need to be generated to better understand what is taking place in the cores of these stars,” Lattanzio said.
The article can be found at: MacLean et al. (2016) An Extreme Paucity of Second Population AGB Stars in the ‘Normal’ Globular Cluster M4.
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Source: Monash University; Photo: Shutterstock.
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