The discovery of massive early galaxies indeed challenges our prior understanding of the universe. According to the standard cosmological model, which is supported by various observations and measurements, the universe started with a period of rapid expansion called inflation, followed by a long period of cooling and gravitational collapse that led to the formation of galaxies and other cosmic structures.
Six massive galaxies discovered in the early universe are challenging scientists’ previous assumptions about the origins of galaxies in the universe.
“These objects are far more massive than anyone expected,” said Joel Leja, an assistant professor of astronomy and astrophysics at Penn State who modeled the light from these galaxies. “At this point in time, we expected to find only tiny, young, baby galaxies, but we’ve discovered galaxies as mature as our own in what was previously thought to be the dawn of the universe.”
Using the first dataset released by NASA’s James Webb Space Telescope, an international team of scientists discovered objects as mature as the Milky Way when the universe was only 3% the age it is now, roughly 500-700 million years after the Big Bang. The telescope is outfitted with infrared sensors capable of detecting light emitted by the most ancient stars and galaxies. According to Leja, the telescope allows scientists to see back roughly 13.5 billion years, near the beginning of the universe as we know it.
The revelation that massive galaxy formation began extremely early in the history of the universe upends what many of us had thought was settled science. We’ve been informally calling these objects ‘universe breakers’ and they have been living up to their name so far.
Joel Leja
“Because this is our first look back this far, we must keep an open mind about what we see,” Leja said. “While the data suggests they are most likely galaxies, I believe a few of these objects could be obscured supermassive black holes. Regardless, the amount of mass discovered implies that the known mass in stars at this time in our universe is up to 100 times greater than previously thought. Even if we divide the sample in half, this is still a remarkable difference.”
In a paper published in Nature, the researchers show evidence that the six galaxies are far more massive than anyone expected and call into question what scientists previously understood about galaxy formation at the very beginning of the universe.
“The revelation that massive galaxy formation began extremely early in the history of the universe upends what many of us had thought was settled science,” said Leja. “We’ve been informally calling these objects ‘universe breakers’ – and they have been living up to their name so far.”
Leja explained that the team’s discovered galaxies are so massive that they contradict 99% of cosmological models. Accounting for such a large amount of mass would necessitate either changing cosmological models or revising scientific understanding of galaxy formation in the early universe – that galaxies began as small clouds of stars and dust that grew larger over time. He went on to say that either scenario necessitates a fundamental shift in our understanding of how the universe came to be.
“We looked into the very early universe for the first time and had no idea what we were going to find,” Leja said. “It turns out we found something so unexpected it actually creates problems for science. It calls the whole picture of early galaxy formation into question.”
On July 12, NASA released the first full-color images and spectroscopic data from the James Webb Space Telescope. The largest infrared telescope in space, Webb was designed to see the genesis of the cosmos, its high resolution allowing it to view objects too old, distant or faint for the Hubble Space Telescope.
“When we got the data, everyone just started diving in and these massive things popped out really fast,” Leja said. “We started doing the modeling and tried to figure out what they were, because they were so big and bright. My first thought was we had made a mistake and we would just find it and move on with our lives. But we have yet to find that mistake, despite a lot of trying.”
Leja explained that taking a spectrum image of the massive galaxies would be one way to confirm the team’s discovery and alleviate any remaining concerns. This would provide the team with information on the true distances as well as the gasses and other elements that comprised the galaxies. The data could then be used to create a more detailed model of what the galaxies looked like and how massive they truly were.
“A spectrum will tell us right away whether or not these things are real,” Leja said. “It will show us how big they are and how far they are away. What’s funny is that we have a long list of things we want to learn from James Webb, and this was nowhere near the top of the list. We discovered something we never thought to ask the universe for – and it happened much faster than I expected, but here we are.”
