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Context: The recent discovery of five massive star clusters from the early Universe, dating back to approximately 460 million years after the Big Bang, represents a significant milestone in our understanding of cosmic history.

Key Highlights

• Early Universe Context: The Universe, as we know it, is approximately 13.6 billion years old. The newly discovered star clusters formed when the Universe was only about 460 million years old, making them among the oldest known star clusters.
• Discovery Details: These star clusters were found within the Cosmic Gems arc, which is part of a galaxy observed using the Hubble Space Telescope and the James Webb Space Telescope. The Cosmic Gems arc is a distant galaxy that allows astronomers to observe cosmic events from 97% of the way across cosmic time.
• Significance of the Discovery: These clusters provide a window into the early stages of galaxy formation and evolution. They are unusually massive and dense for their young age, indicating intense star formation in the early Universe.
• Implications for Reionization: During the early phases of the Universe's history, galaxies underwent significant bursts of star formation. This process generated large amounts of ionizing radiation, which played a crucial role in reionizing the Universe after the Cosmic Dark Ages. The discovery of these star clusters contributes to our understanding of how galaxies in the early Universe contributed to this reionization process.
• Comparative Study with Globular Clusters: In the Milky Way and other mature galaxies, globular clusters are ancient relics of early star formation. The newly discovered clusters may provide insights into the formation processes that eventually led to the creation of these globular clusters.

Star clusters

Star clusters are large groups of stars held together by gravitational attraction. There are several types of star clusters, each with distinct characteristics:

• Globular Clusters: These are spherical clusters containing tens of thousands to millions of stars. They are very old, almost as old as the Universe itself, and composed mainly of old Population II stars (low metallicity). Globular clusters are found in the halo of galaxies, including our Milky Way, and are tightly bound by gravity.
• Open Clusters: Also known as galactic clusters, these are younger and less densely packed than globular clusters. They contain a few hundred to a few thousand stars and are found within the disk of spiral galaxies, often in the spiral arms. Open clusters are loosely bound and are more susceptible to disruption over time due to gravitational interactions with giant molecular clouds and other clusters.
• Embedded Clusters: These are clusters of very young stars still embedded within the dense clouds of gas and dust from which they formed. They are often associated with ongoing star formation regions like molecular clouds. Embedded clusters can contain various types of young stellar objects, such as protostars and pre-main-sequence stars.
• Super Star Clusters: These are regions of intense star formation that can contain hundreds of thousands to millions of stars, forming in extreme environments such as merging galaxies or other high-density regions. They are thought to be precursors to globular clusters.
• Intermediate Forms: There are also intermediate forms of star clusters, such as extended globular clusters found in some galaxies like Andromeda. These clusters are larger and less dense than typical globular clusters but share some similarities.

Astronomical Significance

• Star clusters are important in astronomy because they provide insights into stellar evolution and galaxy formation.
• They serve as natural laboratories to study the properties and behaviour of stars, as all stars within a cluster share similar ages and compositions.
• Studying star clusters helps calibrate the cosmic distance ladder, which is essential for measuring distances in the Universe.
• Star clusters, especially young ones, can also reveal information about the star formation history of galaxies and their evolution over time.

In summary, star clusters play a crucial role in our understanding of the cosmos, from the formation of individual stars to the evolution of entire galaxies. Each type of cluster offers unique insights into different stages of stellar and galactic evolution.

Source:

Indian Express

Wikipedia

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