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Early Galaxies and the Star Formation

Early Galaxies and the Star Formation

The James Webb Space Telescope (JWST) is on a mission to uncover the mysteries surrounding the birth of the first stars and galaxies. Through its Advanced Deep Extragalactic Survey (JADES), the JWST aims to shed light on fundamental questions about how the early galaxies formed and the fascinating process of star birth. Already, JADES has made remarkable discoveries, revealing hundreds of galaxies that existed when the universe was just 600 million years old. These findings provide crucial insights into the early universe and the captivating phenomenon of star formation.

The Epoch of Reionization and the Role of Galaxies

Around 500 to 850 million years after the Big Bang, the universe was shrouded in a dense fog that prevented intense light from passing through. This fog dissipated through a process called reionization, which made the cosmos transparent about one billion years after the Big Bang. Scientists have long debated the role of galaxies in this reionization process and the mechanisms behind star formation.

Ryan Endsley from the University of Texas at Austin and his team examined galaxies from this intriguing period using the JADES program. By studying the light emitted by these galaxies with Webb’s NIRSpec instrument, they made a fascinating discovery. These galaxies exhibited strong indications of recent and vigorous star formation, indicating their proficiency in producing new stars. The energetic ultraviolet light emitted by these stars played a pivotal role in ionizing atoms and clearing the surrounding fog, contributing to the reionization of the universe.

Star Formation Dynamics in Early Galaxies

Endsley and his colleagues also found evidence of cyclic patterns of rapid star formation followed by quieter periods with fewer stars being born. These cycles may have been influenced by the availability of raw materials needed for star formation. Alternatively, the explosive deaths of massive stars may have injected energy into their surroundings, temporarily hindering the formation of new stars.

Revealing the Early Galaxies

Another objective of the JADES program is to identify the earliest galaxies in the universe, which emerged around 400 million years after the Big Bang. By studying these galaxies, astronomers can gain insights into the unique processes involved in the formation of stars during the universe’s infancy. The expansion of the universe causes light from distant galaxies to stretch, resulting in longer wavelengths and redder hues, known as redshift. Measuring the redshift of a galaxy provides astronomers with an estimate of its distance and its age during the early cosmos.

Kevin Hainline from the University of Arizona and his team played a crucial role in this endeavor. Using Webb’s NIRCam instrument, they obtained measurements known as photometric redshifts, which helped identify over 700 candidate galaxies that existed between 370 and 650 million years after the Big Bang. These findings surpassed previous expectations, as earlier measurements had only detected a few hundred galaxies at redshifts above 8, indicating a younger universe. The exceptional resolution and sensitivity of the JWST have provided astronomers with an unprecedented view of these ancient galaxies, revealing their structures and even capturing the formation of star clusters just a few hundred million years after the universe’s birth.


The James Webb Space Telescope’s JADES program is revolutionizing our understanding of early galaxies and the captivating process of star formation. By uncovering hundreds of galaxies from the universe’s infancy and studying their intense star-forming activities, JADES offers valuable insights into the processes that shaped our cosmos. The discoveries made so far suggest that star formation in the early universe was a complex phenomenon influenced by various factors. Through the remarkable capabilities of the JWST, we are gaining a deeper understanding of the origin and evolution of stars.

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