Latest news with #JorisWitstok
Yahoo
28-04-2025
- Science
- Yahoo
Scientists use the JWST to study an extremely ancient galaxy piercing through the Cosmic Dark Ages
When you buy through links on our articles, Future and its syndication partners may earn a commission. Astronomers have caught an immensely ancient galaxy piercing the veil of darkness that shrouded the early universe. It's surprising any light from distant galaxy JADES-GS-Z13-1-LA reached Earth at all. Photons coming from the realm that recently landed on the James Webb Space Telescope's mirrors existed when the universe was just 330 million years old — and, at that point in its adolescence, the universe was foggy and dim. A dense haze of gas suffused the space between stars, and even between galaxies, absorbing starlight and muffling the whole universe in darkness. Astronomers call this period the Cosmic Dark Ages, and JADES-GS-Z13-1-LA is the earliest light we've seen (so far) piercing that cosmic fog. More than 13.5 billion years ago, JADES-GS-Z13-1-LA blazed brightly in ultraviolet light — but as that light crossed billions of light-years between its home galaxy and the Milky Way (which were moving farther apart the whole time, thanks to the fact that the universe is still expanding in the wake of the Big Bang, so everything is still getting farther apart from everything else), its waves stretched out. As a result, the distant galaxy's ultraviolet light had become infrared light by the time it reached the Milky Way. Infrared is invisible to humans, but it's indeed visible to the sensitive instruments aboard the JWST, like the Near-Infrared Camera, Near-Infrared Spectrometer, and Mid-Infrared Instrument. University of Copenhagen astrophysicist Joris Witstok and his colleagues used data from those instruments to shed light on a mysterious period in our universe's distant past: the Epoch of Reionization. Also known as Cosmic Dawn, this was the moment when the light of the first galaxies began to clear away the dense fog that had filled the universe — and absorbed ultraviolet light — around 400,000 years after the Big Bang. JADES-GS-Z13-1-LA is right on the cusp of that crucial moment in our universe's history. It's among the pioneers of reionization and one of the oldest galaxies we can actually see. And that means it can teach physicists about how that process happened and how the earliest galaxies evolved. "I think one of the most intriguing questions about reionization is whether we can pinpoint the very first moment it started across the Universe," Witstok told "which should coincide with the formation of the first generation of stars." By around 300 million years after the Big Bang, the first stars had coalesced from the universe's primordial cloud of matter. Nuclear fusion deep inside these stars was churning out the very first starlight of the cosmos. At the same time, a dense fog of hydrogen gas with a little helium mixed in filled the universe and absorbed the starlight. The Cosmic Dark Ages were in full swing. The all-pervading fog formed as the universe slowly cooled down from the tremendous heat and pressure of the Big Bang. At first, all the matter that had burst into existence with the Big Bang was bouncing around in the form of positively charged protons and negatively charged electrons (well, the protons had probably started as quarks, which eventually stuck together to make protons). Those particles eventually slowed down enough to catch hold of each other and form atoms. Together, those atoms made up a thick haze of hydrogen and helium, exhibiting no electrical charge. That dense, neutral fog absorbed ultraviolet light and acted like a cosmic blackout curtain hung between the galaxies. But ultraviolet radiation changed the cloud itself in the process, knocking electrons off atoms and giving the gas an electric charge (or ionizing it, as physicists would say). Ionized gas, also called plasma, absorbs energy differently than neutral gas does, so galaxies' light at that time had begun to pierce the veil. Light from JADES-GS-Z13-1-LA would have created a bubble of reionized plasma around itself. And, by the time the light passed beyond the bounds of that bubble — about 650,000 light-years, according to Witstok — its wavelengths would have stretched enough that at least some of it would have been able to pass through the intergalactic cloud. University of Melbourne astrophysicist Michele Trenti, who was not involved in the study, tells she's curious about how those bubbles of plasma grew and overlapped over time during the Epoch of Reionization, until the whole universe was eventually reionized — and transparent. Witstok and his colleagues noticed that the light from JADES-GS-Z13-1-LA looked bluer than they expected (meaning that more of it came from the shorter-wavelength end of the electromagnetic spectrum). The galaxy is also giving off a surprising amount of a type of light called Lyman-α radiation. This Lyman-α radiation happens when neutral hydrogen gets a blast of ultraviolet radiation, which excites its electron. As the electron settles back down, it lets off that energy as Lyman-α radiation. The presence of so much Lyman-α in the galaxy's spectrum suggests it's bombarding the surrounding hydrogen with a lot of ultraviolet radiation. "These two facts combined make the galaxy unique (and therefore surprising)," says Trenti, "and [they're] inconsistent with expectations from typical galaxies we see at the end of reionization [around 0.8 billion to 1 billion years after the Big Bang]." Explaining the galaxy's surprisingly energetic glow requires something else surprising: Either JADES-GS-Z13-1-LA is bustling with unusually massive, hot blue stars, or it has an unusually huge supermassive black hole at its center that's actively gobbling up gas. If we're seeing the light from the galaxy's billions of stars, those stars would have to be huge and hot: about 15 times hotter than the sun, and more than a hundred times more massive. On the other hand, if we're seeing the light from a voraciously feeding supermassive black hole, it would have to be even more massive than the one at the heart of our Milky Way, which boasts the mass of about 4 million suns. For most of the models of how galaxies (and the supermassive black holes at their centers) formed and grew, that's a shocking idea: so early in our universe's history, no supermassive black hole should have had time to grow to such a gargantuan size. "There are certain theoretical models where this would be expected though, so if this were the case it could have very important implications for such theories for early black hole formation," says Witstok. For Trenti, this is one of the most interesting questions about the Epoch of Reionization: "What are the sources of radiation that contribute to reionization? Is the process driven by normal stars, exotic stars, or accreting black holes?" The answer could tell us something about how early galaxies formed and evolved into ones like our Milky Way and its thoroughly modern neighbors. But Witstok and his colleagues still don't have enough information to solve that particular mystery. "This discovery starts shining some light on when reionization started, but it is just a preview that stirs curiosity, it is hard to do science with a sample of only one object," said Trenti. Witstok agrees, but he's optimistic about finding more galaxies from the cusp of the Epoch of Reionization – and so far, JWST has been pushing the boundaries of how far back in time astronomers can see. Related Stories: — James Webb Space Telescope finds a wild black hole growth spurt in galaxies at 'cosmic noon' — Has the James Webb Space Telescope discovered a 'missing' supermassive black hole? (video) — Is our universe trapped inside a black hole? This James Webb Space Telescope discovery might blow your mind "I'm sure over the next years we will find examples of even more distant galaxies with similar characteristics,' Witstok said. "The next steps include investigating this galaxy in more detail, with new observations already having been obtained and more scheduled to be taken in the near future, but also finding more examples of galaxies with very bright Lyman-α radiation very early on." If astronomers can get more detailed measurements of the spectrum of light coming from the galaxy, they may be able to measure how much helium, oxygen and carbon are involved in producing the light. That will let them compare JWST's measurements to computer models of the physics involved and see which explanation best matches the data. The study was published on March 26 in the journal Nature.
Reuters
26-03-2025
- Science
- Reuters
Webb telescope spots galaxy at pivotal moment in the early universe
WASHINGTON, March 26 (Reuters) - Scientists using the James Webb Space Telescope have identified an ancient and faraway galaxy that provides evidence that an important transition period that brought the early universe out of its "dark ages" occurred sooner than previously thought. Webb, which by peering across vast cosmic distances is looking way back in time, observed the galaxy called JADES-GS-z13-1 as it existed about 330 million years after the Big Bang event that initiated the universe roughly 13.8 billion years ago, the researchers said. By way of comparison, Earth is about 4.5 billion years old. The universe is thought to have experienced a rapid and exponential expansion in a fraction of a second after the Big Bang. After having cooled down sufficiently, there was a period called the cosmic dark ages when the infant universe was enveloped in a dense fog of hydrogen gas in an electrically neutral state. What followed that was a time called the epoch of reionization when the universe first began to shine. Webb obtained evidence that JADES-GS-z13-1, one of the earliest-known galaxies, had made the transition into this epoch. "In JADES-GS-z13-1, Webb has confirmed one of the most distant galaxies known to date," said astrophysicist Joris Witstok of the University of Copenhagen's Cosmic Dawn Center and the Niels Bohr Institute, lead author of the study published in the journal Nature, opens new tab. "Unlike any other similarly distant galaxy, it shows a very clear, telltale signature that suggests the galaxy contains a remarkably powerful source of energetic ultraviolet radiation and has made an unexpectedly early start to reionization," Witstok said. The time when the universe's first stars, black holes and galaxies formed is called cosmic dawn. As these formed, the ultraviolet radiation they emitted chemically altered the neutral hydrogen gas in a process called reionization and allowed ultraviolet light to escape, effectively "turning on the lights" in the cosmos. "The universe, after the Big Bang, was a soup of hydrogen, helium and dark matter, slowly cooling off. Eventually, the universe was in a state where it was entirely opaque to energetic ultraviolet radiation. Hydrogen was floating around in a neutral state, meaning each little hydrogen atom had an electron bound to it," said astrophysicist and study co-author Kevin Hainline of the University of Arizona's Steward Observatory. "But as the first stars and galaxies started to form from this early universe gas, the ultraviolet radiation from young stars and from growing supermassive black holes began to knock electrons off of these neutral hydrogen atoms. And over hundreds of millions of years the universe transitioned from being opaque to ultraviolet light to transparent to ultraviolet light, which is where we are now," Hainline said. The researchers said the light that Webb detected in this galaxy may have come from vigorous star formation in the galaxy's nucleus, the presence of a growing supermassive black hole at the galactic core that is violently consuming surrounding material or some combination of those two factors. This galaxy measures about 230 light-years wide, several hundred times smaller than the Milky Way. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). Webb, which was launched by NASA in 2022 and became operational in 2023, has begun to provide a deeper understanding of the early universe. It has spotted only four galaxies dating to slightly earlier than this one, including the current record holder observed at 294 million years after the Big Bang. Those galaxies have not displayed evidence of reionization. The researchers were stunned to find that JADES-GS-z13-1 showed such evidence - in the form of a large bubble of ionized hydrogen surrounding it - because reionization was thought to have started many millions of years later. "Many independent measurements have firmly established that reionization was not fully completed until the universe was about one billion years old - 700 million years later than this galaxy - placing this galaxy at what is likely the start of the reionization era. When exactly it began is one of the big outstanding questions in cosmology," Witstok said.
