NASA’s James Webb Space Telescope Finds Most Distant Known Galaxy

Editor’s Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.

Over the last two years, scientists have used NASA’s James Webb Space Telescope (also called Webb or JWST) to explore what astronomers refer to as Cosmic Dawn – the period in the first few hundred million years after the big bang where the first galaxies were born. These galaxies provide vital insight into the ways in which the gas, stars, and black holes were changing when the universe was very young. In October 2023 and January 2024, an international team of astronomers used Webb to observe galaxies as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. Using Webb’s NIRSpec (Near-Infrared Spectrograph), they obtained a spectrum of a record-breaking galaxy observed only two hundred and ninety million years after the big bang. This corresponds to a redshift of about 14, which is a measure of how much a galaxy’s light is stretched by the expansion of the universe. We invited Stefano Carniani from Scuola Normale Superiore in Pisa, Italy, and Kevin Hainline from the University of Arizona in Tucson, Arizona, to tell us more about how this source was found and what its unique properties tell us about galaxy formation.

“The instruments on Webb were designed to find and understand the earliest galaxies, and in the first year of observations as part of the JWST Advanced Deep Extragalactic Survey (JADES), we found many hundreds of candidate galaxies from the first 650 million years after the big bang. In early 2023, we discovered a galaxy in our data that had strong evidence of being above a redshift of 14, which was very exciting, but there were some properties of the source that made us wary. The source was surprisingly bright, which we wouldn’t expect for such a distant galaxy, and it was very close to another galaxy such that the two appeared to be part of one larger object. When we observed the source again in October 2023 as part of the JADES Origins Field, new imaging data obtained with Webb’s narrower NIRCam (Near-Infrared Camera) filters pointed even more toward the high-redshift hypothesis. We knew we needed a spectrum, as whatever we would learn would be of immense scientific importance, either as a new milestone in Webb’s investigation of the early universe or as a confounding oddball of a middle-aged galaxy.

Alt text: A field of thousands of small galaxies of various shapes and colors on the black background of space. A bright foreground star with diffraction spikes is at lower left. Near image center, a tiny white box outlines a region and two diagonal lines lead to a larger box in upper right, enlarging the view of this area. Within the box is a banana-shaped blob that is blueish-red in one half and distinctly red in the other half. An arrow points to the redder portion and is labeled “JADES GS z 14 0 .” — This infrared image from NASA’s James Webb Space Telescope (also called Webb or JWST) was taken by the NIRCam (Near-Infrared Camera) for the JWST Advanced Deep Extragalactic Survey, or JADES, program. The NIRCam data was used to determine which galaxies to study further with spectroscopic observations. One such galaxy, JADES-GS-z14-0 (shown in the pullout), was determined to be at a redshift of 14.32 (+0.08/-0.20), making it the current record-holder for the most distant known galaxy. This corresponds to a time less than 300 million years after the big bang.
In the background image, blue represents light at 0.9, 1.15, and 1.5 microns (filters F090W + F115W + F150W), green is 2.0 and 2.77 microns (F200W + F277W), and red is 3.56, 4.1, and 4.44 microns (F356W + F410M + F444W). The pullout image shows light at 0.9 and 1.15 microns (F090W + F115W) as blue, 1.5 and 2.0 microns (F150W + F200W) as green, and 2.77 microns (F277W) as red.
Credit: NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA)

“In January 2024, NIRSpec observed this galaxy, JADES-GS-z14-0, for almost ten hours, and when the spectrum was first processed, there was unambiguous evidence that the galaxy was indeed at a redshift of 14.32, shattering the previous most-distant galaxy record (z = 13.2 of JADES-GS-z13-0). Seeing this spectrum was incredibly exciting for the whole team, given the mystery surrounding the source. This discovery was not just a new distance record for our team; the most important aspect of JADES-GS-z14-0 was that at this distance, we know that this galaxy must be intrinsically very luminous. From the images, the source is found to be over 1,600-light years across, proving that the light we see is coming mostly from young stars and not from emission near a growing supermassive black hole. This much starlight implies that the galaxy is several hundreds of millions of times the mass of the Sun! This raises the question: How can nature make such a bright, massive, and large galaxy in less than 300 million years?

“The data reveal other important aspects of this astonishing galaxy. We see that the color of the galaxy is not as blue as it could be, indicating that some of the light is reddened by dust, even at these very early times. JADES researcher Jake Helton of Steward Observatory and the University of Arizona also identified that JADES-GS-z14-0 was detected at longer wavelengths with Webb’s MIRI (Mid-Infrared Instrument), a remarkable achievement considering its distance. The MIRI observation covers wavelengths of light that were emitted in the visible-light range, which are redshifted out of reach for Webb’s near-infrared instruments. Jake’s analysis indicates that the brightness of the source implied by the MIRI observation is above what would be extrapolated from the measurements by the other Webb instruments, indicating the presence of strong ionized gas emission in the galaxy in the form of bright emission lines from hydrogen and oxygen. The presence of oxygen so early in the life of this galaxy is a surprise and suggests that multiple generations of very massive stars had already lived their lives before we observed the galaxy.

Alt text: A graph labeled “Galaxy JADES GS z 14 0, Galaxy existed 300 million years after big bang, NIRSpec microshutter array spectroscopy.” The x-axis is labeled “Wavelength of Light, microns” and extends from about 0.5 microns to 5.5 microns, with tick marks every 0.5 microns from 1.0 to 5.0. The y-axis is labeled “Brightness” and has a zero mark with a horizontal, dashed line about a third of the way up from the bottom. An up arrow is labeled “brighter.” A jagged orange line runs horizontally across the graph. It fluctuates above and below the zero line until reaching a wavelength of about 1.9 microns, at which point it peaks before gradually decreasing again, but remaining above the zero line. The wavelength where the emission peaks has a vertical red line labeled “Lyman-alpha break, z = 14.32.” — Scientists used NASA’s James Webb Space Telescope’s NIRSpec (Near-Infrared Spectrograph) to obtain a spectrum of the distant galaxy JADES-GS-z14-0 in order to accurately measure its redshift and therefore determine its age. The redshift can be determined from the location of a critical wavelength known as the Lyman-alpha break. This galaxy dates back to less than 300 million years after the big bang.
Credit: NASA, ESA, CSA, Joseph Olmsted (STScI). Science: S. Carniani (Scuola Normale Superiore), JADES Collaboration.

“All of these observations, together, tell us that JADES-GS-z14-0 is not like the types of galaxies that have been predicted by theoretical models and computer simulations to exist in the very early universe. Given the observed brightness of the source, we can forecast how it might grow over cosmic time, and so far we have not found any suitable analogs from the hundreds of other galaxies we’ve observed at high redshift in our survey. Given the relatively small region of the sky that we searched to find JADES-GS-z14-0, its discovery has profound implications for the predicted number of bright galaxies we see in the early universe, as discussed in another concurrent JADES study (Robertson et al., recently accepted). It is likely that astronomers will find many such luminous galaxies, possibly at even earlier times, over the next decade with Webb. We’re thrilled to see the extraordinary diversity of galaxies that existed at Cosmic Dawn!”

These spectroscopic observations were taken as part of Guaranteed Time Observations (GTO) program 1287, and the MIRI ones as part of GTO program 1180.

About the authors:
Stefano Carniani is an assistant professor at Scuola Normale Superiore in Italy. He is also a member of the Webb/NIRSpec GTO team and studies galaxy and black hole evolution across cosmic time.

Kevin Hainline is an associate research professor at the Steward Observatory, University of Arizona. He is also a member of the Webb/NIRCam Science team, and is using data from the JADES GTO survey to explore the evolution of galaxies and active galactic nuclei at the highest redshifts.

News Media Contacts:

Alise Fisher
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Laura Betz
Goddard Space Flight Center, Greenbelt, Md.
301-286-9030
laura.e.betz@nasa.gov

Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
410-338-4366
cpulliam@stsci.edu