An impressive picture of a 'globular cluster' that contains thousands, if not millions of glittering stars were released by NASA recently. The Hubble Space Telescope captured the image of the globular cluster NGC 6569 in the Sagitarrius constellation.
Globular clusters are stable and tightly bound groups that contain tens of thousands to millions of stars. They are bound together in a tight gravitational bond and are usually much larger than open clusters. The strong gravitational bond between the stars gives them the speherical shape hence the name 'globular'.
Globular clusters usually contain older, redder stars more than in open clusters. Redder stars in open clusters usually disperse before they become old. Strong gravity also provides stability in globular clusters resulting in a longer life span, allowing stars to reach billions of years of age.
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Star clusters of all kind are of equal and great interest to astronomers because the constituent stars would have approximately been formed at the same time and locations having similar internal compositions. Thus the clusters offer useful insights into the formation and evolution of stars. However, studying individual stars within globular clusters is not possible because of their tightly-wound shape.
The new image from Hubble comes from an investigation of globular clusters which lay close to the centre of the Milky Way galaxy. Previous studies did not venture into this because the dusty centre of the galaxy blocks out light from the clusters and also alters the colours of the stars within them. A star's colour helps astronomers determine its age, composition and temperature.
The scientists who made these observations combined information from Hubble with data from astronomical archives, which allowed them to measure the ages of globular clusters like NGC 6569. Their research also helped give insights into the structure and density of globular clusters towards the centre of the Milky Way.