How did the first galaxies after the Big Bang form and evolve? Were they small and attributed to dark matter or were they large and some other force attributed to their growth? This is what a recent study published in The Astrophysical Journal hopes to address as a team of researchers challenged longstanding hypotheses that the first galaxies in the universe were formed from dark matter, instead being formed from an alternate theory of gravity. This study holds the potential to help researchers better understand the formation and evolution of early galaxies and the processes responsible for their growth.
“Astronomers invented dark matter to explain how you get from a very smooth early universe to big galaxies with lots of empty space between them that we see today,” said Dr. Stacy McGaugh, who is a Professor and Director of Astronomy at Case Western Reserve University and lead author of the study. “The expectation was that every big galaxy we see in the nearby universe would have started from these itty-bitty pieces.”
For the study, the researchers used NASA’s powerful James Webb Space Telescope to observe some of the earliest galaxies that existed less than 1 billion years after the Big Bang, designated by a redshift of z = 10, which is a system that astronomers use to determine how long light has been traveling before it reaches Earth. This is because when astronomers look at celestial objects, they’re looking back in time, and measuring the change in light wavelength can help determine the length of time the light has been traveling.
Image of some of the earliest galaxies observed by NASA’s James Webb Space Telescope. (Credit: NASA)
In the end, the researchers found that these early galaxies were much larger and formed much faster than longstanding cosmological models and theories had predicted, which stated the dark matter could have been responsible for the formation of early galaxies. However, this new study found that no dark matter was responsible for the formation of these early galaxies, instead a stronger form of gravity is being labeled as the culprit.
What new discoveries about early galaxies will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: The Astrophysical Journal, EurekAlert!
