AMHERST, Mass. — A team of 48 astronomers from 14 countries, led by the University of Massachusetts Amherst, has discovered a population of dusty, star-forming galaxies at the far edges of the universe that formed only a billion years after the Big Bang, believed to have occurred 13.7 billion years ago.
The galaxies may represent a snapshot in the galactic lifecycle, linking recently discovered ultradistant bright galaxies formed 13.3 billion years ago with early "quiescent," or dead, galaxies that stopped forming stars about 2 billion years after the Big Bang. The new discovery challenges current models of the universe, making the findings, published in The Astrophysical Journal Letters , is a step toward revising cosmic history.
"My research involves trying to identify and understand a population of rare, dusty star-forming galaxies that were only discovered at the end of the 1990s," says Jorge Zavala , assistant professor of astronomy at UMass Amherst and the paper's lead author.
Part of what has made these galaxies so difficult to study is the dust, which absorbs UV and visible light, essentially making them invisible to telescopes that rely on the UV and visible parts of the spectrum.
But with the invention of submillimeter telescopes, which can see longer-wavelength light, suddenly astronomers were able to shine a light into dusty parts of the universe that had previously remained dark. As the dust absorbs UV and visible light, it also creates heat—radiating infrared energy visible to these telescopes.
Zavala and his co-authors relied on the Atacama Large Millimeter/sub millimeter Array (ALMA) telescope in Chile to first identify a population of about 400 bright, dusty galaxies. They then used near-infrared observations made by NASA's recently launched James Webb Space Telescope to pinpoint approximately 70 faint dusty galaxy candidates on the edge of our universe, most of which had never been seen before. By going back to the ALMA data and "stacking" the observations, the team was able to confirm that these are in fact dusty galaxies formed almost 13 billion years ago.
While technical knowledge necessary to make this discovery is itself newsworthy, the real story is about what this discovery means for our understanding of the history of the universe.
"Dusty galaxies are massive galaxies with large amounts of metals and cosmic dust," Zavala says. "And these galaxies are very old, which means stars were being formed in the early universe, earlier than our current models predict."
Furthermore, it seems that the galaxies Zavala and his team found are related to two other sets of rare, anomalous galaxies: the ultrabright, star-forming galaxies that formed soon after the Big Bang (recently discovered by JWST), and much older, massive "quiescent" galaxies, that have essentially died and are no longer forming stars.
"It's as if we now have snapshots of the lifecycle of these rare galaxies," Zavala notes. "The ultrabright ones are young galaxies, the quiescent ones are in their old age, and the ones we found are young adults."
Though it will take much more research to confirm these suggestions, if Zavala and his team's hypothesis holds true, it means both that our current astronomical models of the universe's formation are missing something, and that star formation occurred earlier in the universe's evolution than previously thought.
Zavala points out that this research would not have been possible without the collaboration of scientists and institutions from across the world, including funding from the U.S. National Science Foundation.
