Stars of Varied Ages Can Coexist in Open Clusters

The chemical clouds that make up our Galaxy are what give rise to stars. The majority of stars in our Galaxy are thought to develop in stellar clusters, making them crucial to understanding the star formation mechanism. 

Astronomers at the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous science institute under the Department of Science and Technology (DST), have discovered that stars of different ages can coexist in open clusters. This contradicts previous assumptions that all stars in an open cluster are the same age.

Stars: 

A star is a compact ball of gas with an incandescent surface heated by the energy released by nuclear reactions (fusion) within the star. The equilibrium between the inward force of gravity and the outward pressure of expansion owing to the energy released by nuclear fusion determines the size and temperature of a star. The more massive a star is, the faster its nuclear fuel is burned, and the brighter it glows.

Stellar Evolution: 

Every star undergoes a complex process of continuous change, and their life cycle consists of immature, mature, and final changes as they near the end of their lives called stellar evolution.

Stars go through an evolutionary sequence that can be divided into three parts: pre-main sequence, main sequence, and post-main sequence. The Main Sequence Star is a star that is currently in the main mature period of its life cycle which are in an equilibrium state as they convert hydrogen into helium. Pre-main sequence stars or infant stars are stars that have not yet entered the main sequence. Post-main sequence or elderly stars are stars that have already lived their main sequence lives.

Open Stars Clusters: 

Open clusters are loosely connected collections of stars ranging in size from a few tens to a few hundred. Spiral and irregular galaxies contain them.

Compared to globular clusters, open clusters are substantially smaller and sparsely populated. The number of stars in an open cluster might range from a few tens to several hundred. Open clusters have been discovered with a variety of ages, indicating that they could be made up of young or older stars. They are not very stable due to their open and diffuse structure, and their constituent stars may disperse within a few million years.

Aryabhatta Research Institute of Observational Sciences (ARIES): 

ARIES was founded in 1955 and moved to its current location at Manora Peak in 1961. This observatory, which houses one of the best and most modern telescopes in India, was established in Nainital due to the area’s pristine skies. In 2004, it became an autonomous agency within the Department of Science and Technology (DST), Government of India.

ARIES is one of the most prestigious research institutes in the fields of astronomy, astrophysics, and atmospheric sciences. Solar, planetary, stellar, galactic, and extragalactic astronomy, including X-ray binaries, star clusters, neighboring galaxies, quasars, and fundamentally transitory events like a supernova and very powerful gamma-ray bursts, is the division’s core study interests.  

About the discovery: 

We can study the evolution of a group or cluster of stars rather than a single star. Looking for a cluster of stars that are incredibly close in space, locked together by gravity, and often orbit a common core. Then it’s plausible to suppose that each of the group’s individual stars formed at around the same time, from the same cloud, and with the same composition.

The light from three poorly studied open clusters NGC 381, NGC 2360, and Berkeley 68 was monitored using the 1.3-m telescope at Devasthal in the Himalayan foothills to explore the evolution of stars in these clusters. The researchers discovered two distinct stellar evolutionary sequences in the cluster NGC 2360, which had previously only been seen in a few open clusters in the Milky Way Galaxy.

Their research was recently published in the OXFORD University Press’s ‘Monthly Notices of the Royal Astronomical Society,’ a premier magazine in the field of astronomy and astrophysics.

How Stars Of Varied Ages Can Coexist In Open Clusters: 

We anticipate that the sole difference between these stars will be their mass. And their numbers dictate how rapidly they go through life stages.

We can find clusters in which large stars have already completed their main-sequence phase of evolution and become red giants, while stars of lower mass in the same cluster are still on the main sequence, or even undergoing pre-main-sequence gravitational contraction if the cluster is very young. We can see multiple stages of star evolution among the members of a single cluster, and thus we can test if our theories can explain why H–R diagrams of clusters of various ages appear the way they do.

Conclusion: 

Within the Milky Way, some 1100 open clusters have been identified so far, with much more likely to exist which could be researched more thoroughly due to the discovery that stars of varied ages can coexist in open clusters. The well-known Carina Nebula region of space contains one of the Milky Way’s largest concentrations of huge, bright stars.