Astronomers at the Peking University in China have found how glittering globular clusters for new generations of stars. According to a study published in the journal Nature, globular star clusters draw in stray gas and dust from their neighboring galaxy to produce new generations of stars. Globular star clusters are densely packed, ancient, spherical swarms of millions of stars orbiting the outskirts of galaxies.
Globular clusters more complex than previously thought
Dr Richard de Grijs, the co-author of the study, said star clusters “have turned out to be much more complex than we previously thought.” Previously, all the stars in a globular cluster were believed to be the same age. About a decade ago, astronomers discovered that even globular star clusters that are more than 10 billion years old often have younger stars.
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It indicates that more than one star-forming events might have occurred. In a globular cluster, the first stellar generation contains very large stars. The death of these massive stars in a cluster generates powerful supernova explosions that blow away any star-forming gas in the cluster. The cluster becomes gas free in 3 million to 10 million years, quenching further star formation.
So, how could there be new waves of star formation in globular clusters? Astronomers used archival data from the Hubble space telescope to study one globular cluster NGC 411 in the Small Magellanic Cloud and two clusters NGC 1783 and NGC 1696 in the Large Magellanic Cloud. Astronomers can figure out the age of stars by examining their color and brightness.
Star clusters experienced more than one star-forming events
Researchers have strong evidence that globular star clusters have younger stars because they experienced more than one star-forming event. They found that these three clusters contain stars that are a few hundred million years younger than the main stellar population. The younger stars make up only 0.2% to 2% the masses of those clusters.
Astronomers calculated that the clusters were able to pull in additional gas and dust from the gaseous disks of their galaxies while orbiting. They could have collected enough stray dust and gas to trigger formation of a new generation of stars. Findings of the study could shed light on how the globular star clusters evolve.