The earliest galaxy the James Webb Space Telescope has spotted so far formed 325 million years after the big bang. A computer model shows this early period as massive stars (yellow) scatter heavy elements in supernovae (round objects, left), and two galaxies take shape (right), pulling stars and gas into gravitationally bound structures.
SIMULATION: COSMIC RENAISSANCE, JOHN WISE, TOM ABEL, BRIAN O’SHEA, MICHAEL NORMAN. VISUALIZATION: RALF KAEHLER AND TOM ABEL, STANFORD UNIVERSITY/KIPAC/SLAC.
Below Article is taken from
Naional Geographic Magazine - October 2023 issue
BY JAY BENNETT
PUBLISHED SEPTEMBER 14, 2023
When the universe was young, more than 13 and a half billion years ago, no stars shone in the abyss. Astronomers call this era the dark ages, a time when the cosmos was filled with hydrogen and helium gas, the raw material for all the worlds to come.
A mysterious substance known as dark matter existed too, its gravity pulling the gas into an elaborate web. As things expanded and cooled, some of the dark matter consolidated in immense orbs, driving the gas to their cores. The rising gravitational pressure within these halos, as astronomers named them, forced hydrogen atoms to fuse into helium, igniting the primordial universe’s first stars.
I watched the spark of cosmic dawn, through 3D glasses. Sitting in front of a projector at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, I marveled at filaments of dark matter, a ghostly gray on the screen, branching between halos as the universe stretched. Maelstroms of newly born stars spiraled to the centers of the halos to form the first galaxies.
Scientists have been filling in the universe’s origin story for decades, but in the past year, the largest and most advanced space telescope ever built has rewritten the first chapters. Ancient galaxies glimpsed by the James Webb Space Telescope (JWST) are brighter, more numerous, and more active than anticipated, revealing a frenetic opening to the saga of space and time.
Webb cannot see the first stars, though, as they weren’t bright enough to detect individually. These early monsters blazed hot and grew immense before erupting in supernovae a few million years after flaring to life—a blip in astronomical time.
“We really slowed things down a little bit here,” said Tom Abel, a computational cosmologist and my guide through the simulations. He wore an earring of a human figure curled in the fetal position; it reminded me of the closing shot of 2001: A Space Odyssey, where a child in a womb floats in space. “It’s just so crazy fast. The full realistic version would have been much faster flashes.
In one of the deepest views into the universe ever achieved, the Webb telescope reveals thousands of stars and galaxies, including the bright light-warping cluster in the center.
COMPOSITE BY NASA, ESA, CSA, STSCI
Those flashes, the supernovae of stars up to hundreds of times the mass of the sun, transformed the universe. New elements were generated—oxygen to make water, silicon to build planets, phosphorus to power cells—and scattered throughout the expanse. The first stars also broke apart the atoms of the surrounding hydrogen gas, burning away the cosmic haze and making things transparent—a key time known as reionization. As the fog lifted, pockets of stars merged, swirling into bigger and bigger assemblages, including the seed of our own Milky Way.
Abel began modeling the birth of the first stars in the 1990s, when no one knew what the earliest astronomical object was, whether a black hole or a Jupiter-size body or something else. Through computer simulations, he and his colleagues helped determine that the first things had to be stars, kindled in places where gravity slowly won out over gas pushing outward. But eventually Abel moved on from star-birth simulations; he thought there was nothing more to learn.
Then came Webb.
Launched on Christmas morning in 2021, the space telescope is now positioned nearly a million miles from Earth. Its 21-foot-4-inch gold-coated primary mirror captures the light of ancient galaxies, which has been traveling through space for more than 13 billion years, revealing the galaxies as they were in the distant past. (How do you create a telescope unlike anything we’ve had before? These photos show us.)
Astronomers expected to find some of these infant galaxies with Webb. They didn’t expect to find so many—or that the discoveries could shake their understanding of galactic history.
Only four of the five galaxies known as Stephan’s Quintet are truly close together, pulling at one another in a swirling dance. The unprecedented detail provided by Webb gives scientists an opportunity to study how the interaction between galaxies may have driven their early evolution.
COMPOSITE BY NASA, ESA, CSA, AND STSCI
In this region of the Orion Nebula where ultraviolet radiation from a nearby star cluster is driving intense chemical reactions, Webb recently discovered methyl cation. The carbon compound—never before detected in space—facilitates the formation of more complex carbon molecules, which are needed for life.
COMPOSITE BY ESA/WEBB, NASA, CSA, M. ZAMANI (ESA/WEBB), PDRS4ALL ERS TEAM
The deepest galaxy survey of the universe ever undertaken kicked off in September 2022, when an international collaboration known as JADES, or the JWST Advanced Deep Extragalactic Survey, began using Webb to observe patches of sky for dozens of hours at a time. Two weeks after observations began, the collaboration gathered in Tucson at the University of Arizona to discuss the first results.
In a modern five-story building with a large, open-air atrium designed to evoke a slot canyon, some 50 astronomers packed into a classroom. A handful stood at the back or brought in extra chairs to sit along the walls. “I’m going to have to start reserving bigger rooms,” said Marcia Rieke, an astronomer at the university and one of the leaders of the collaboration.
Astronomers Marcia and George Rieke have played key roles in the development and operation of Webb instruments—the near-infrared camera, or NIRCam, and the mid-infrared instrument, or MIRI, respectively, both of which were used to create the projected image of dusty clouds ejected from a burning star.
CHRIS GUNN (RIEKES); COMPOSITE OF 104 IMAGES BY NASA, ESA, CSA, STSCI, WEBB ERO PRODUCTION TEAM
The scientists, from tenured professors to twentysomething graduate students, were preoccupied with the mosaic on their laptops: hundreds of images freshly captured by Webb and stitched together. The picture, shared with the team only days before, contained tens of thousands of galaxies and other celestial objects. Excited murmuring ran through the group as they pointed out things to one another that had never been seen: active star-forming regions, glowing galactic centers where black holes might be, and reddish blobs of light from galaxies so distant only Webb could spot them.
“This is a little bit like kids in the candy shop,” Rieke said to me.
Unlike the Hubble Space Telescope, our previous window into the universe’s distant past, Webb was designed to observe in the infrared, which makes it ideal for capturing early starlight. Those rays left their source as ultraviolet but were stretched to redder wavelengths by the expansion of the universe, a phenomenon known as redshift. The higher the redshift, the farther and older the target.
Rieke managed the proceedings with a combination of unfeigned delight and sage reflection, chiming in to answer a technical question or ambling over to a team member between talks to discuss the workings of the telescope. Besides being a lead scientist on JADES, she’s the principal investigator of Webb’s near-infrared camera, or NIRCam—the source of the mosaic of galaxies on everyone’s laptop. She oversaw its design, a 330-pound assemblage of mirrors, lenses, and detectors to drink in the light of the universe and study it through different filters.
“These images are everything we could have hoped for,” she said.
But not everything on the telescope was functioning perfectly. JADES’s near-infrared spectrograph, or NIRSpec, had been experiencing electrical shorts that created spots of light and drowned out astronomical targets in some of the observations. The instrument splits light into spectra, allowing scientists to piece together the chemical composition of a galaxy and precisely measure its redshift. While the NIRCam images could be used to estimate the distances to galaxies, NIRSpec was needed to confirm them.
The electrical shorts delayed some of the team’s observations, a development that turned out to be serendipitous. The astronomers had planned to use NIRSpec to examine objects already known from Hubble, but now they could change the targets to galaxies only just discovered by NIRCam.
“We just went crazy looking through this data that no one had ever seen, looking for these candidates,” Kevin Hainline, an astrophysicist at the University of Arizona, told me later in his office.
One thing the team couldn’t do was change where the telescope was pointing. It had to find objects already in the field of view—and thanks to a bit of luck, four faraway galaxies detected by NIRCam were sitting in the right spot. Two of those, NIRSpec observations would later confirm, were more distant and ancient than any known before.
The most far-flung of the bunch, called JADES-GS-z13-0, had been formed only 325 million years after the big bang. “I still have the Slack message where I first saw this object in the data and sent it to the group,” Hainline said. “In the craziness of it, I didn’t realize the profundity of this moment of sitting there and being like, Oh, that’s the farthest galaxy that humans have ever seen.”
Two things are already clear about these early galaxies: There are more of them than expected, and they are surprisingly bright for their age. These anomalies could be because the first stars formed more efficiently than thought or there was a larger proportion of big stars than hypothesized. “However star formation gets going in the early universe, it’s not quite like how we might have predicted,” Rieke says.
One early galaxy, GN-z11 from some 440 million years after the big bang, is bright enough that Hubble spotted it in 2016. Now Webb has observed the object as well, including taking its spectrum with NIRSpec.
Distant galaxies are not the only way to learn about the primordial cosmos. Nearby dwarf galaxies, such as Wolf-Lundmark-Melotte (in an image from the European Southern Observatory’s VLT Survey Telescope in Chile), contain small stars that formed early in the universe and are still around today.
EUROPEAN SOUTHERN OBSERVATORY (ESO)
Webb has now peered into the Wolf-Lundmark-Melotte galaxy (both images) to study some of these ancient, slow-burning stars—fossils from earlier eras.
NASA; ESA; CSA; KRISTEN MCQUINN, RUTGERS UNIVERSITY; ZOLT G. LEVAY; ALYSSA PAGAN (STSCI)
“This one has everyone sort of confused and excited,” says Emma Curtis-Lake, an astrophysicist at the University of Hertfordshire in England and a member of the NIRSpec team.
Certain elements create bright emission lines in a galaxy’s spectrum, like fingerprints by galactic material. The spectrum of GN-z11 revealed a surprising amount of nitrogen—confounding scientists, who can’t explain its source. Perhaps a population of raging hot stars known as Wolf-Rayet stars scattered nitrogen in pulses of stellar wind. Or maybe several large stars collided, mixing up the material in their cores and surfaces and releasing nitrogen in the process.
GN-z11 may also host a supermassive black hole, which would be remarkable for this early time. It’d be “the most distant black hole that we’ve seen,” Curtis-Lake says.
Obscured at the center of the bright galaxy, it was exposed by spectral lines that Curtis-Lake calls “little hidden monsters.” These lines suggest that material is moving rapidly in a dense area, swirling at roughly a million miles an hour—the kind of thing you would expect to see near a black hole. But how one of these objects could have grown so rapidly remains unsolved.
The reddish bar running through galaxy NGC 1300 funnels gas to the center, triggering rapid star formation. The Hubble Space Telescope made this detailed image of the nearby barred spiral galaxy, showing what such a galaxy looks like today. Webb has found much earlier ones, including those below. “We did not expect barred galaxies to be present at such early epochs,” says astronomer Shardha Jogee, whose team was led by graduate student Yuchen Guo.
NASA,ESA, AND THE HUBBLE HERITAGE TEAM (STSCI/AURA)
Read the full findings at
Naional Geographic Magazine - October 2023 issue
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