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Webb’s oldest galaxies challenge our cosmological theories

These six potential massive galaxies were captured in images taken 500-800 million years following the Big Bang. Credit for the image goes to NASA/ESA/CSA/I. Labbe.

Since the dawn of time, humans have been captivated by the mysteries of the universe. From the stars in the sky to the smallest particles on Earth, we have been constantly seeking answers to our most profound questions. In recent years, astronomers have made incredible discoveries about the origins of our universe, but there is still much that remains unknown. One of the most fascinating areas of study is the formation of galaxies, and the discovery of the oldest galaxies in the universe has challenged our understanding of cosmological theories.

James Webb Space Telescope Reveals Puzzling Galaxies

The James Webb Space Telescope (JWST) seems to be uncovering several galaxies that developed too large, too quickly after the Big Bang, challenging the conventional model of cosmology.

Mike Boylan-Kolchin, an associate professor of astronomy at The University of Texas at Austin, has published a study in Nature Astronomy that presents six of the earliest and most massive galaxy candidates discovered by JWST, which defy existing cosmological beliefs. According to other researchers, these galaxies are observed 500 to 700 million years post-Big Bang and possess a mass over 10 billion times that of our sun. Astonishingly, one of these galaxies even surpasses the Milky Way in mass, despite having billions of fewer years to form and grow.

Uncharted Territory and New Theories

Boylan-Kolchin said, “If the masses are right, then we are in uncharted territory.” To explain these findings, scientists may need to propose new theories about galaxy formation or modify cosmology. One extreme possibility suggests that the universe expanded faster shortly after the Big Bang than predicted, potentially requiring the introduction of new forces and particles.

For these massive galaxies to form so quickly, they would also need to convert nearly 100% of their available gas into stars. Boylan-Kolchin noted that this is highly unusual, as “We typically see a maximum of 10% of gas converted into stars.”

Astronomers Face Dilemma: Challenging the ΛCDM Paradigm

The JWST’s discoveries have forced astronomers to confront a troubling dilemma. If these galaxies’ masses and age are confirmed, it may necessitate significant changes to the dark energy + cold dark matter (ΛCDM) paradigm that has governed cosmology since the late 1990s. This shift would require a reevaluation of current theories about how galaxies form and the amount of matter available for star and galaxy formation in the early universe.

The six galaxies’ initial mass and time estimates require follow-up confirmation using spectroscopy—a method that analyzes the brightness of different colors in a light spectrum. This analysis could reveal that supermassive black holes at the galaxies’ centers are heating surrounding gas, making the galaxies appear more massive than they truly are. Alternatively, dust may cause the galaxies’ light to appear redder, giving the illusion that they are further away and, thus, further back in time.

Future Research and Collaborative Projects

The data was obtained from the Cosmic Evolution Early Release Science Survey (CEERS), a multi-institution JWST project led by UT Austin astronomer Steven Finkelstein. Another collaborative JWST project, COSMOS-Web, co-led by UT Austin’s Caitlin Casey, may use spectroscopy to provide further insight into these findings and help resolve the dilemma. COSMOS-Web is anticipated to discover thousands of galaxies as it covers an area about 50 times larger than CEERS.

Boylan-Kolchin expressed optimism about COSMOS-Web’s capacity, stating, “It will be ideal for discovering the rarest, most massive galaxies at early times, which will tell us how the biggest galaxies and black holes in the early universe arose so quickly.” The initial identification and estimates of the six candidates were published in Nature in February by a research team from Swinburne University of Technology in Australia. The National Science Foundation and NASA provide support for this research.

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