This artist’s concept shows what the universe might have looked like when it was less than a billion years old, about 7 percent of its current age. Star formation voraciously consumed the primordial hydrogen, churning out multitudes of stars at an unprecedented rate. NASA’s Roman Nancy Grace Space Telescope will look back at the early stages of the universe to understand how it went from being dark to the brilliant starscape we see today.
NASA, ESA and A. Schaller (for STScI)
Today, vast stretches of space are crystal clear, but it wasn’t always this way. During its beginning, the universe was filled with a “fog” that made it dark, covering the first stars and galaxies. NASA’s upcoming Nancy Grace Roman Space Telescope will probe the universe’s later transition into the brilliant starscape we see today — an era known as the cosmic dawn.
“Something very fundamental about the nature of the universe changed during this time,” said Michelle Thaller, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Thanks to Roman’s large and sharp infrared image, we can finally understand what happened during a critical cosmic turning point.”
Lights off, lights on
Immediately after his birth, the cosmos was a sea of cocoons of particles and radiation. As the universe expanded and cooled, positively charged protons were able to capture negatively charged electrons to form neutral atoms (mostly hydrogen, plus some helium). This was good news for the stars and galaxies that atoms would eventually become, but bad news for light!
It likely took a long time for gaseous hydrogen and helium to coalesce into stars, which then gravitated together to form the first galaxies. But even when the stars began to shine, their light could not travel very far before striking and being absorbed by neutral atoms. This period, known as the cosmic dark ages, lasted from about 380,000 to 200 million years after the big bang.
The nebula then slowly lifted as more and more neutral atoms disintegrated over the next several hundred million years: a period called the cosmic dawn.
“We’re very curious about how the process happened,” said Aaron Yung, a Giacconi Fellow at the Space Telescope Science Institute in Baltimore, who is helping plan early observations of the Roman universe. “Roman’s big, clear view of deep space will help us weigh different explanations.”
The main suspects
It may be that the early galaxies may be largely to blame for the energetic light that exploded the neutral atoms. The first black holes may also have played a role. Roman will look far and wide to examine both possible culprits.
“Roman will excel at finding the building blocks of cosmic structures like galaxy clusters that form later,” said Takahiro Morishita, an assistant scientist at Caltech/IPAC in Pasadena, California, who has studied the cosmic dawn. “It will quickly identify the densest regions where the most ‘fog’ is being cleared, making Roman a key mission to probe early galactic evolution and the cosmic dawn.”
The earliest stars were likely completely different from modern ones. When gravity began to pull material in, the universe was very dense. The stars probably grew hundreds or thousands of times more massive than the Sun and emitted a lot of high-energy radiation. Gravity gathered the young stars to form galaxies, and their cumulative explosion may once again have stripped electrons from protons into bubbles of space around them.
“You could call it the party at the beginning of the universe,” Thaller said. “We never saw the birth of the first stars and galaxies, but it must have been spectacular!”
But these heavyweight stars were short-lived. Scientists think they collapsed quickly, leaving behind black holes — objects with gravity so extreme that even light cannot escape their clutches. Since the young universe was also smaller because it hadn’t been expanding very long, a bunch of those black holes could have merged to form even bigger ones — up to millions or even billions of times the mass of the Sun .
Supermassive black holes may have helped clear the hydrogen haze that permeated the early universe. Hot material swirling around black holes in the bright centers of active galaxies, called quasars, before falling in can generate extreme temperatures and send out large, bright jets of intense radiation. Jets can stretch for hundreds of thousands of light years, stripping electrons from every atom in their path.
NASA’s James Webb Space Telescope is also exploring the cosmic dawn, using its narrower but deeper view to study the early universe. By combining Webb’s observations with Roman’s, scientists will create a much more complete picture of this era.
So far, Webb is finding more quasars than expected given their expected rarity and Webb’s small field of view. Roman’s zoomed-in view will help astronomers understand what’s going on by seeing how common quasars really are, likely finding tens of thousands compared to the tiny ones Webb can find.
This view from the James Webb Space Telescope features more than 20,000 galaxies. The researchers analyzed 117 galaxies that all existed roughly 900 million years after the big bang. They focused on 59 galaxies that lie in front of the quasar J0100+2802, an active supermassive black hole that acts like a beacon, located at the center of the image above appearing small and pink with six visible diffraction spikes. The team studied both the galaxies themselves and the luminous gas surrounding them, which was ignited by the quasar’s bright light. The observation sheds light on how early galaxies cleared the “fog” around them, eventually leading to today’s clear, extended views.
NASA, ESA, CSA, Simon Lilly (ETH Zürich), Daichi Kashino (Nagoya University), Jorryt Matthee (ETH Zürich), Christina Eilers (MIT), Rob Simcoe (MIT), Rongmon Bordoloi (NCSU), Ruari Mackenzie (ETH Zürich ); Image processing: Alyssa Pagan (STScI), Ruari Macken
“With a stronger statistical sample, astronomers will be able to test a wide range of theories inspired by Webb’s observations,” Yung said.
Looking into the universe’s first hundreds of millions of years with Roman’s open-eyed view will also help scientists determine whether certain types of galaxies (such as more massive ones) played a larger role in clearing the haze. .
“It could be that the young galaxies started the process and then the quasars finished the job,” Yung said. Seeing the size of the bubbles etched by the fog will give scientists a big clue. “Galaxies would create large clusters of bubbles around them, while quasars would create large spherical ones. We need a large field of view like the Roman one to measure their extent, since in both cases they are possible up to millions of light-years across — often larger than the Web’s field of view.”
Roman will work side-by-side with Webb to provide clues about how galaxies formed from the primordial gas that once filled the universe and how their central supermassive black holes influenced galaxy and star formation. The observations will help reveal the cosmic dawns that lit up our universe and eventually made life on Earth possible.
The Roman Nancy Grace Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation from NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team composed of scientists from various. research institutions. Key industrial partners are BAE Systems, Inc in Boulder, Colorado; L3Harris Technologies in Rochester, New York; and Teledyne Scientific & Imaging in Thousand Oaks, California.
Download high-resolution videos and images from NASA’s Science Visualization Studio
By Ashley Balzer
NASA Goddard Space Flight Center, Greenbelt, Md.
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