The James Webb Space Telescope is the most powerful out of outer space. It allows astronomers to study further, earlier galaxies, helping usher in a new era of astrophysics. As scientists look into the distant history of the universe, they are shocked to find galaxies that appeared in cosmic history much sooner than expected.
Issues of Early Galaxies
On July 12, 2022, the NASA Goddard Spaceflight Center released the first images captured by the James Webb Space Telescope (JWST). Among them was the detailed image of SMACS 0723, which shows galaxy clusters and the gravitational lenses they produced. These enabled astronomers to peer deeper into the cosmos and locate galaxies as they appeared less than one billion years after the Big Bang. Further examination revealed surprising details about the early galaxies, as most are much larger than expected.
The standard model of cosmology suggests that the earliest galaxies in the universe did not have enough time to be as massive, bright, and mature as they appeared. This raised questions about the current cosmological models and whether the universe is older than previously thought.
The brightness of a galaxy is usually determined by mass. The more massive a galaxy is, the brighter it appears through the telescopes. More massive galaxies also hold more stars, which suggests a highly advanced stage of galactic evolution that allowed billions of stars to form.
Astronomers are puzzled as to how such mature galaxies form in such a short period during the early stage of the universe. It has even led some scientists to rethink that the universe might be two times older than the 13.8-billion-year estimate accepted by the scientific community.
New Star Theory
Astrophysicists led by Guochao Sun from Northwestern University tried solving this problem using computer simulations. Their findings point to bright, irregular bursts of star formation, which led to less massive galaxies that can glow just as bright.
The research team simulated the formation of early galaxies as part of the FIRE (Feedback In Realistic Environments) project, where computer simulations combine astrophysical theory with advanced algorithms. In this project, researchers could model galaxy formation, growth, and development by accounting for mass, energy, momentum, and chemical elements returned from stars.
When the simulation was run, it was found that stars are made in bursts, which take place when they form in an alternating pattern. This "bursty star formation" is rare in massive galaxies such as the Milky Way, where stars form steadily and increase gradually over time. In contrast, many stars formed at once in early galaxies, followed by millions of years where very few new stars were formed before a new burst occurred.
The study's findings suggest that the early galaxies may not be so massive. They could have appeared larger due to irregular and very bright bursts of star formation. The research also highlights a major difference between galaxies as they existed in the early universe versus today. Modern galaxies are primarily composed of older stars commonly found closer to the center of the galaxies. There are also metal-rich stars that have just recently formed and are commonly found in the spiral arms of galaxies. In contrast, the earliest galaxies were populated by stars with no heavy elements and were massive and bright.
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