An international team of astronomers used data from NASA’s James Webb Space Telescope to report the discovery of the oldest confirmed galaxies to date. The light from these galaxies took more than 13.4 billion years to reach us, because these galaxies had a history less than 400 million years after the Big Bang, when the universe was only 2% of its current age.

Previous Webb data provided candidates for such nascent galaxies. These goals have now been confirmed by obtaining spectroscopic observations that reveal distinctive and characteristic patterns in fingerprints of light from incredibly faint galaxies.

“It was extremely important to prove that these galaxies did indeed live in the early universe. It is possible that nearby galaxies look like very distant galaxies,” said astronomer and co-author Emma Curtis-Lake of the University of Hertfordshire in the US. Kingdom. “As we hoped, seeing the spectrum unfold confirms that these galaxies are at the true limit of our view, a little further away than Hubble can see! This is an extremely exciting achievement for the mission.”

The observations are the result of collaboration between scientists at Webb who led the development of two instruments, the Near Infrared Camera (NIRCam) and the Near Infrared Spectrograph (NIRSpec).

Studying the faintest and oldest galaxies was the main motivation behind the design of these instruments. In 2015, the instrument clusters came together to present the JWST Advanced Deep Extragalactic Survey (JADES), an ambitious program designed to provide an overview of the early universe, dedicating just over a month of the telescope’s two-year runtime. unmatched in both depth and detail.

JADES is an international collaboration of more than eighty astronomers from ten countries. “These results are the culmination of why the NIRCam and NIRSpec teams came together to do this observational program,” said co-author Marcia Riecke, NIRCam principal investigator at the University of Arizona in Tucson.

The first round of JADES observations focused on the region in and around the Hubble Space Telescope’s Ultra Deep Field. For over 20 years, this small piece of sky has been the target of nearly all major telescopes, producing an extremely sensitive dataset covering the entire electromagnetic spectrum. Webb now adds its own unique spin, delivering the brightest and sharpest images ever taken.

The JADES program started with NIRCam, which uses over 10 mission days to observe the field in nine different infrared colors and produce excellent images of the sky. The field is 15 times larger than the deepest infrared images taken by the Hubble Space Telescope, but it’s even deeper and sharper at these wavelengths. An image as tall as a human when viewed from a mile away. However, each one at some point in its history is filled with about 100,000 galaxies from billions of years ago.

“We first discovered galaxies only 350 million years after the Big Bang, and we can be absolutely certain of their fantastic distances,” said co-author Brant Robertson of the University of California, Santa Cruz, a member of the NIRCam Science Team. “Finding these early galaxies in such stunningly beautiful images is a special experience.”

In these images, galaxies in the early universe can be distinguished by the characteristic aspect of their multi-wavelength colors. As the universe expands, light gets longer in wavelength, and light from these youngest galaxies stretches up to 14 times.

Astronomers look for faint galaxies that are visible in the infrared but whose light is suddenly cut off at a critical wavelength. The intersection point in the spectrum of each galaxy is shifted by the expansion of the universe. The JADES team analyzed Webb images to find these perfect candidates.

They then used the NIRSpec tool over an observation period spanning three days, covering a total of 28 hours of data collection. The team collected light from 250 faint galaxies, allowing astronomers to study the patterns in which atoms in each galaxy make their mark on the spectrum. This provided precise measurements of the redshift of each galaxy and revealed the characteristics of the gas and stars in these galaxies.

“These are the weakest infrared spectra ever obtained,” said astronomer and co-author Stefano Carniani of Scuola Normale Superiore in Italy. “They show what we hope to see: a precise measurement of the limiting wavelength of light due to the scattering of intergalactic hydrogen.”

Four of the galaxies studied were particularly special because they were found to belong to an unprecedented early period. The results confirmed spectroscopically that these four galaxies have a redshift of more than 10, and two of them have a redshift of 13. These galaxies are extremely dim because they are so far away from us. Astronomers can now study its features, thanks to Webb’s extraordinary precision.

Astronomer and co-author Sandro Tacchella of the University of Cambridge in the UK explains: “Galaxy is difficult to understand without understanding the early stages of their development. As with humans, much of what happens later is due to the influence of these early generation stars. Many questions about galaxies await Webb’s transformative opportunity, and we are excited to be a part of solving this story.”

In 2023, JADES will continue its detailed work in another area focusing on Hubble’s iconic deep field, before returning to ultra-deep space for another round of deep imaging and spectroscopy. There are many candidates awaiting spectroscopic research in the field, and hundreds of hours of additional time have already been confirmed.