Eighteen
of the recently discovered dusty, star-forming galaxies (in red) formed almost
13 billion years ago. Credit: UMass Amherst
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
life cycle, linking recently discovered ultradistant bright galaxies formed
13.3 billion years ago with early "quiescent" (dead) galaxies that
stopped forming stars about two billion years after the Big Bang.
Challenging what we know about cosmos
The new discovery challenges
current models of the universe, making the findings, published in The Astrophysical Journal Letters,
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.
New tools for seeing hidden galaxies
But with the invention of
submillimeter telescopes, which can see longer-wavelength light, suddenly
astronomers were able to shine 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.
What dusty galaxies reveal about time
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 life cycle 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 the hypothesis of Zavala and his team 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.
Source: Astronomers may have just found one of the missing links in galaxy evolution
