James Webb Space Telescope Traces a Galaxy’s Past Right Back to the Post-Big Bang Era

Astronomers have used the James Webb Space Telescope (JWST) to study the history of stars in a low-mass dwarf galaxy, Wolf–Lundmark–Melotte (WLM), which is similar to the galaxies that filled the early universe. The researchers, led by Kristen McQuinn from Rutgers University-New Brunswick, aim to better comprehend how star formation rates have transformed over the last 13 billion years.

WLM, a neighbor of the Milky Way, resides at the edge of our galaxy’s local group, approximately 3 million light-years away. The dwarf galaxy is not only actively forming stars but also hosts ancient ones, believed to have formed roughly 13 billion years ago, around 800 million years post-Big Bang. Given that galaxies like WLM were thought to have dominated the early universe, they serve as excellent subjects for exploring early star formation rates.

McQuinn likened the study to an archaeological dig, delving into the early history of the universe. The JWST’s impressive observational power has enabled the astronomers to examine these faint galaxies in unprecedented detail. The low-mass galaxies like WLM, while faint, comprise the majority of galaxies in the Milky Way’s local group.

WLM’s location at the edge of the local group has kept it isolated, safeguarding its stellar population from the gravitational influence of other galaxies. This isolation, along with its complex system filled with gas and dust, makes WLM an intriguing subject for astronomers.

The team focused the JWST on regions of the sky corresponding with WLM, which contained hundreds of thousands of individual stars. By measuring the colors and brightness of these stars, the astronomers could estimate their ages. Using the data from JWST, they were able to chart the birth rate of stars over the history of the universe.

The study revealed that star production in WLM has fluctuated, with the most stars being produced over a period of 3 billion years that started between 2 billion and 4 billion years after the Big Bang. This star formation was interrupted before restarting, a pause which McQuinn attributes to the hot conditions of the early universe.

The research showcases the versatility of the JWST, which launched on Christmas Day 2021 and began transmitting data in the summer of 2022. McQuinn believes that the computational effort required to calibrate and process the JWST data could benefit the wider scientific community. The research has been published in the Astrophysical Journal.

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