Evidence of the existence of the first generation of stars in the universe has emerged, thanks to observations made by the James Webb Space Telescope (JWST). The evidence is located in one of the most distant known galaxies.
Designated galaxy GN-Z11was discovered by Hubble Space Telescope In 2015, before the launch of the James Webb Space Telescope, it was considered the most distant known galaxy. with Redshift From 10.6, it makes sense to talk about how long it has been around, not how far away it is. This is because we see GN-z11 as it was only 430 million years after its appearance the great explosion Because of the time it takes for its light to travel to our corner of the universe. By comparison, today's universe is… 13.8 billion years.
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As such, GN-z11 was a prime target for study by the James Webb Space Telescope. Now, two new papers describe profound discoveries about GN-z11 that reveal vital details about how galaxies that existed in the early universe grew.
GN-z11 is the brightest galaxy known at this particular redshift, and indeed this has become a popular subject for high-redshift galaxies now being found almost regularly in the early Universe by the James Webb Space Telescope. Many of them appear brighter than our models of galaxy formation predict. These predictions are based on the Standard Model of cosmology.
Now, new observations by the James Webb Space Telescope appear to have shed light on what's going on.
An astronomy team led by Roberto Maiolino of the University of Cambridge examined GN-z11 using the James Webb Space Telescope's two near-infrared instruments, the Near-Infrared Camera (NIRCam) and the Near-Infrared Spectrometer (NIRSpec). Researchers have discovered evidence of a first generation of stars, called third-group stars, as well as the existence of a cluster of stars Giant black hole They devour huge amounts of matter and grow at a greatly accelerated rate.
Scientists can calculate a star's age based on its abundance of heavy elements, which were created by previous generations of stars that lived and died, spewing those heavy elements out into space where they are eventually recycled in star-forming regions to form new stars. Astral bodies. Younger stars that formed within the last five or six billion years are referred to as first-group stars, and have the highest abundances of heavy elements. Our sun Is the population I star. Older stars contain fewer heavy elements because there were fewer generations of stars that preceded them. We call these second-group stars, and they live in our oldest regions Milky Way.
However, the stars of the third group have been purely hypothetical so far.
These stars were supposed to be the first stars to form, and since there were no other stars before them, they contained no heavy elements and were made only of pure hydrogen and helium that formed during the Big Bang. These first stars are also thought to have been extremely luminous, with masses equivalent to at least several hundred suns.
Although astronomers have yet to see Group III stars directly, Maiolino's team has discovered indirect evidence of them in GN-z11. NIRSpec observed a clump of ionized helium near the edge of GN-z11.
“The fact that we don't see anything other than helium suggests that this mass must be fairly pure,” Maiolino said in his report. statement. “This is something that would have been expected from theory and simulations in the vicinity of particularly massive galaxies from these epochs – that there should be pockets of pristine gas remaining in the halo, and these pockets might collapse and form third-group stars.”
This helium gas is ionized by something that produces huge amounts of ultraviolet light, called Population III stars. The helium we saw is likely a material left over from the formation of those stars. The amount of ultraviolet light needed to ionize all this gas requires about 600,000 solar masses of stars in total, shining a combined luminosity 20 trillion times brighter than our Sun. These numbers suggest that distant galaxies like GN-z11 were more adept at forming massive stars than galaxies in the modern universe.
Meanwhile, according to a second set of results, Maiolino's team also found evidence of a 2 million solar-mass black hole in the core of GN-z11.
“We found very dense gas that is common in the vicinity of supermassive black holes that accumulate gas,” Maiolino said in the same statement. “This was the first clear evidence that GN-z11 hosts a black hole that is devouring matter.”
The team also detected a powerful ice of radiation streaming from the accreting disk of matter orbiting the black hole, as well as ionized chemical elements typically found near accreting black holes. The team says it is the most distant supermassive black hole yet discovered, and its voracious appetite causes its accretion disk to become dense, hot, and shine brightly. Researchers believe that this, combined with Group III stars, is what makes GN-z11 shine so bright. Without breaking standard cosmology As some did Prematurely claimed.
The study on ionized helium mass and Population III stars has been accepted for publication in the journal Astronomy and Astrophysics, and a preprint is available for purchase Found here. Meanwhile, the study of NIRCam observations of the black hole was published on January 17 in the journal nature.
