Six massive galaxies discovered in the early Universe turn on its head what scientists previously understood about the origins of galaxies in the Universe.
“These objects are much more massive? than anyone expected,” said Joel Leja, an assistant professor of astronomy and astrophysics at Penn State University, who modeled the light from these galaxies. “We expected to find only tiny, young baby galaxies at this point, but we have discovered galaxies as mature as our own in what used to be thought to be the beginning of the universe.”
Using the first data set released by NASA’s James Webb Space Telescope, the international team of scientists discovered objects as mature as the Milky Way when the universe was only 3% of its current age, around 500 to 700 million years after Big Bang. The telescope is equipped with infrared-sensitive instruments capable of detecting light emitted by the oldest stars and galaxies. Essentially, the telescope allows scientists to look back in time about 13.5 billion years, near the beginning of the universe as we know it, Leja explained.
“This is our first look so far back, so it’s important that we keep an open mind about what we’re seeing,” Leja said. “Although the data suggests they are likely galaxies, I think there is a real possibility that some of these objects will turn out to be eclipsed supermassive black holes. Regardless, the amount of mass we’ve discovered means that the known mass in stars at this time in our universe is up to 100 times greater than we previously thought. Even if we halve the sample, it’s still an amazing change.”
In a paper published today (February 22) in Naturethe researchers show evidence that the six galaxies are much more massive than anyone expected, and challenge what scientists have understood so far about the formation of galaxies at the dawn of the universe.
“The revelation that the formation of massive galaxies began extremely early in the history of the Universe turns what many of us thought was mainstream science on its head,” Leja said. “We’ve informally dubbed these objects ‘Universe Breakers’ – and they’ve lived up to their name so far.”
Leja explained that the galaxies discovered by the team are so massive that they are in tension with 99 percent of the cosmology models. Accounting for such a high mass would require either a change in models for cosmology or a revision of the scientific understanding of galaxy formation in the early Universe – that galaxies began as small clouds of stars and dust that gradually grew larger over time. Both scenarios require a fundamental shift in our understanding of how the universe formed, he added.
“We looked into the very early universe for the first time and had no idea what we would find,” said Leja. “It turns out we’ve found something so unexpected that it actually creates problems for science. It challenges the whole picture of early galaxy formation.”
On July 12, NASA released the first full-color images and spectroscopic data from the James Webb Space Telescope. Webb, the largest infrared telescope in space, was designed to see the formation of the cosmos, its high resolution allows it to see objects that are too old, distant or faint for the Hubble Space Telescope.
“Once we got the data, everyone started to dive in, and these giant things started showing up really quickly,” Leja said. “We started modeling and trying to figure out what they were because they were so big and bright. My first thought was that we had made a mistake and we would just find it and move on with our lives. But we still have to find this bug, despite many attempts.”
Leja explained that one way to confirm the team’s findings and address any remaining concerns is to take a spectral image of the massive galaxies. That would provide the team with data on true distances, and on the gases and other elements that make up the galaxies. The team was then able to use the data to create a clearer picture of what the galaxies looked like and how massive they really were.
“A spectrum will tell us immediately whether these things are real or not,” Leja said. “It will show us how big they are, how far away they are. The funny thing is that we have all these things that we hope to learn from James Webb, and that was nowhere near the top of the list. We found something we never thought we’d ask the universe for – and it came a lot quicker than I thought it would, but here we are.”
The other co-authors of the publication are Elijah Mathews and Bingjie Wang from Penn State, Ivo Labbe from Swinburne University of Technology, Pieter van Dokkum from Yale University, Erica Nelson from the University of Colorado, Rachel Bezanson from the University of Pittsburgh , Katherine A. Suess from the University of California and Stanford University, Gabriel Brammer from the University of Copenhagen, Katherine Whitaker from the University of Massachusetts and the University of Copenhagen, and Mauro Stefanon from the Universitat de Valencia.