A newly discovered galaxy has broken the record for the earliest observed galaxy, posing a major challenge to our current models of galaxy formation.
Called JADES-GS-z14-0, it shines brightly in the early universe, as it was less than 300 million years after the Big Bang. A second recent discovery, called JADES-GS-z14-1, turned out to be almost as distant.
The detections, astronomers say, are now “unambiguous,” meaning Cosmic Dawn may have some “explanations” to provide.
“In January 2024, NIRSpec observed this galaxy, JADES-GS-z14-0, for nearly ten hours, and when the spectrum was first processed, there was unambiguous evidence that the galaxy was indeed at a redshift of 14.32, breaking the previous record for the most distant galaxy,” said astronomers Stefano Carniani of the Scuola Normale Superiore in Italy and Kevin Hainline of the University of Arizona.
“According to the images, the source is more than 1,600 light-years across, proving that the light we see comes primarily from young stars and not from emission from nearby a growing supermassive black hole.
“Such a large amount of starlight implies that the galaxy has a mass several hundred million times that of the Sun! This raises the question: how could nature have created such a bright, massive and large galaxy in less than 300 million years?”
Three separate articles have been written on the subject, one of which has just been published in Nature.
Two more on arXiv have yet to be peer-reviewed, but all three have the same conclusion: JADES-GS-z14-0 is definitely there, a bright data point that represents a new path forward in understanding how the Universe formed, in the very beginning.
Location of JADES-GS-z14-0. (NASA, ESA, CSA, STScI, Brant Robertson/UC Santa Cruz, Ben Johnson/CfA, Sandro Tacchella/Cambridge, Phill Cargile/CfA)
Until recently, we had very little concrete knowledge about the period known as the Cosmic Dawn, the first billion years after the Big Bang 13.8 billion years ago. This is because the early Universe was filled with a fog of neutral hydrogen that scattered light, preventing it from propagating.
This fog did not last; it was ionized and dissipated by ultraviolet light emitted by objects in the early Universe, and by the end of the Cosmic Dawn, space was transparent.
But at that time, there were already a whole bunch of stars and galaxies hovering around us. If we want to understand how it all formed, we need to be able to see through the fog.
This is one of the functions that the JWST, with its powerful infrared eyes, was designed for. Infrared radiation is able to penetrate dense media, something light cannot do, its long wavelengths being able to pass through with minimal scattering.
The JWST’s Advanced Deep Extragalactic Survey (JADES) has been searching for objects that occurred in the first 650 million years after the Big Bang, with some very interesting results.
We have repeatedly observed that large objects appear much earlier than expected. This is quite astonishing, because we have always thought that supermassive black holes and galaxies take a long time to form, much longer than the time span over which we observe them.
But JADES-GS-z14-0 takes the cake. It is very large and very bright, which is not at all what astronomers had predicted galaxies would look like in the early Universe.
First, its size shows that most of the light must come from stars, rather than the burst of light from space around a growing supermassive black hole.
The spectrum of JADES-GS-z14-0. (NASA, ESA, CSA, Joseph Olmsted/STScI)
Analysis of its light reveals the presence of a lot of dust and oxygen, which is unexpected at this early stage. Such heavy elements should be made inside stars that are then to explode. These characteristics suggest that several generations of massive stars must have lived and died already 300 million years after the Big Bang.
Given that today’s largest stars have lifespans of only a few million years, this isn’t impossible, but it’s still not quite what astronomers expected to find.
Overall, this galaxy suggests that we need to rethink the early Universe, showing that the large number of bright sources we see there cannot be entirely explained by the growth of black holes. Somehow, large, bright, well-formed galaxies may have been assembling at the beginning of the cosmic dawn.
“JADES-GS-z14-0 now becomes the archetype of this phenomenon,” Carniani said. “It is astonishing that the Universe could create such a galaxy in just 300 million years.”
The discovery article led by Carniani was published in NatureOther papers studying the properties of galaxy light can be found on arXiv here and here.
An earlier version of this article was published in May 2024.
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