A large group of stars in the nearby globular cluster known as M4 have died prematurely (in a stellar sense) and no one knows why. Should we be worried? Is it something contagious?
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 both fascinating and frustrating at the same time.
Professor John Lattanzio from Australia’s Monash University described the frustration he and his colleagues are experiencing as they study Messier 4 (M4), a globular cluster in the Scorpius constellation that was catalogued by Charles Messier in 1764 and is the first globular cluster in which individual stars were identified. Globular clusters of stars are held together by gravity in a tight sphere with an extreme central density. M4 is one of the nearest and brightest and has been well-studied. Yet the sudden deaths of many of its stars came as a surprise to astronomers.
Using a new high efficiency and resolution multi-element spectrograph (HERMES) on the Anglo Australian Telescope (AAT) of the Australian Astronomical Observatory (AAO), Lattanzio and his team were able to analyze the chemical compositions of large groups of M4 stars and found that half of them skip the Red Giant phase (dying star) and go right to becoming White Dwarfs (dead but not yet a black hole), dying millions of years before they’re supposed to.
What’s killing these stars prematurely? Dr Simon Campbell says HERMES shows that they are sodium-rich but oxygen-poor stars, but that alone is not enough to explain the mass deaths.
Although the phenomenon of sodium-rich stars failing to reach old age has been seen in our previous research, it was totally unexpected that it should occur on such a scale in this ‘normal’ star cluster.
The astronomers were also caught by surprise because computer simulations conflict with these observations. They plan to adjust the models while continuing to monitor M4.
Should we be worried about our own Sun dying prematurely? It’s not a Red Giant yet but that last eclipse was a little weak …