Astronomers using the James Webb Space Telescope (JWST) have made an incredible discovery: the most distant known quiescent galaxy. This find shows that some massive galaxies stopped forming stars much earlier than we expected—only 700 million years after the Big Bang.
The galaxy, called RUBIES-UDS-QG-z7, was detected during the JWST’s second observation cycle as part of a study led by a European team known as the RUBIES survey. With over 10 billion solar masses compacted into a region merely 650 light-years wide, it’s both dense and small.
What’s remarkable about RUBIES-UDS-QG-z7 is that it’s quiescent—meaning it stopped forming stars when the universe was still in its infancy. This finding challenges long-standing beliefs about how long it takes for massive galaxies to form and eventually stop star formation.
Lead author Andrea Weibel, a doctoral student at the University of Geneva, explains, “The discovery of this galaxy implies that massive quiescent galaxies in the first billion years of the universe are more than 100 times more abundant than predicted by any model to date.” This suggests a major shift in our understanding of galaxy formation.
Early End to Star Formation
Traditionally, astronomers believed galaxies accumulate gas and convert it into stars over time. Eventually, this star-making process stops, a phenomenon called “quenching.” Until now, it was thought that quenching takes a significant amount of time. However, with the advanced infrared tools of JWST, scientists can catch glimpses of very distant galaxies and analyze their light.
The spectroscopic data from RUBIES-UDS-QG-z7 reveals an old stellar population, predominantly older, red stars, indicating that the galaxy had already finished its stellar life cycle. Anna de Graaff, a key investigator in the RUBIES program, adds, “This galaxy provides strong evidence that the centers of some massive elliptical galaxies might have formed quite early in the universe’s timeline.”
Crisis for Theoretical Models
Before this discovery, the earliest known quiescent galaxies were about 1.2 billion years old—this galaxy pushes that back by 500 million years and raises questions about current models explaining how galaxies form. As Pascal Oesch, a professor at the University of Geneva, points out, understanding the formation mechanisms behind these early massive quiescent galaxies is vital.
Current models struggle to account for how such a dense and massive galaxy can evolve and stop star formation at such an early stage. Astronomers now believe that factors like stellar winds, feedback from supermassive black holes, and galactic outflows could influence star formation more significantly than previously thought.
Historical Context
Historically, the study of galaxies has evolved tremendously. In the past, astronomers could only observe much younger galaxies, and their understanding of how galaxies age and evolve was limited. Today’s technology, like the JWST, offers powerful tools for unraveling these mysteries, propelling our knowledge into new frontiers.
Ancient Origins of Galaxies
The structure of RUBIES-UDS-QG-z7 resembles the core features of giant elliptical galaxies we see today. This suggests that massive galaxies might have had their foundational elements in place much sooner than we previously believed.
The discoveries surrounding RUBIES-UDS-QG-z7 provide critical insights into the universe’s evolution, hinting at a rich history of galaxy formation. As we continue to explore the distant universe, we may uncover even more surprises that can reshape our understanding of cosmic history. For further information, check out a detailed study published in the Astrophysical Journal and learn more about the incredible capabilities of the JWST.
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