Earlier this year, Euclid—a European telescope tasked with creating the largest 3D map of the universe—sent back troves of cosmic data from deep space. Since then, astronomers have been hard at work analyzing the stars, with one team arriving at a surprising conclusion about the fate of the universe.
By studying both Euclid’s optical measurements and far-infrared data from the now-concluded Herschel mission, a team of 175 astronomers constructed the most detailed heat map of the universe to date. This temperature map strongly suggests that star formation in our universe has already passed its peak rates and that galaxies have begun to cool down.
In short, our universe is “already past its prime,” the researchers noted in a statement. “The Universe will just get colder and deader from now on,” added Douglas Scott, study author and cosmologist at the University of British Columbia in Canada.
The paper describing these results has been submitted for publication to *Astronomy & Astrophysics* and is currently available as a preprint on arXiv.
### As the Cosmic Dust Settles
For their analysis, the researchers examined heat emission data from 2.6 million galaxies captured by Euclid. Specifically, they used a stacking method to trace the evolution of stardust and relevant heat signals over the past 10 billion light-years of the universe’s history. They then made adjustments to account for factors such as redshift—the shift in the wavelengths of a galaxy’s light as it moves away from us.
According to the study, average dust temperatures have not changed much from around 35 Kelvin (approximately -396°F or -238°C) in the universe’s early days. Over 10 billion years, dust temperatures fell by only about 10 Kelvin, or roughly 18°F.
This is significant because the temperature of galactic dust is strongly linked to the rate of star formation. Simply put, hotter galaxies form more stars, while cooler galaxies form fewer.
The small yet clear downward trends in galactic dust temperatures and dust loads imply that our universe is gradually becoming populated with cooler galaxies. “We’re past the epoch of maximum star formation,” Scott explained.
### A Distant Future
If anything from this gradual cosmic cooling is to be felt on Earth, it won’t happen for at least tens of billions of years. Still, the findings are impressive because the astronomers leveraged an enormous dataset to draw insightful conclusions about galaxies—the building blocks of the cosmos.
“In the past, researchers wouldn’t have a large enough sample or might be missing key populations of cold or hot galaxies,” said Ryley Hill, an astrophysicist at the University of British Columbia who led the research. “Since Euclid is so comprehensive, you can really measure dust temperatures in a way you can’t argue with.”
### New Questions on the Horizon
If the universe is indeed slowing down in terms of star formation, it opens up a whole new set of questions for researchers to explore. What does this imply about dark energy or dark matter? Since this is only the first batch of Euclid data, will future releases reveal something completely different? Will current cosmological models continue to stand up to scrutiny?
None of these questions will be easy to answer. So, even if the universe’s star formation is past its prime, humanity’s research journey is far from over.
https://gizmodo.com/our-universe-is-getting-colder-deader-astronomers-say-2000683693