NASA's James Webb has discovered the oldest galaxy ever observed

NASA's James Webb has discovered the oldest galaxy ever observed

Over the past two years, scientists have used NASA's James Webb Space Telescope (JWST) to explore a very special period in the universe called the cosmic dawn, which includes the first few hundred million years after the Big Bang, when the first galaxies began to appear. Form.

These early galaxies are extremely important because they help us understand how gases, stars and black holes changed in the young universe.

Between 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) programme.

The JADES-GS-z14-0 galaxy, as it appeared 290 million years after the Big Bang, as seen by NASA's James Webb Space Telescope (JWST). Image credit: NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Taccella (Cambridge), Phil Cargill (CfA)

James Webb saw the galaxy just 290 million years after the Big Bang

They used an instrument at Webb called the Near-Infrared Spectrometer (NIRSpec) to obtain a spectrum of the galaxy seen just 290 million years after the Big Bang. This equates to a redshift of about 14, which means that the galaxy's light has been stretched by the expansion of the universe.

Stefano Cargnani, from the Normal High School in Pisa, Italy, and Kevin Heinlein, from the University of Arizona, in Tucson, USA, led the observations and reveal more about the discovery. In the current situation Released this Thursday (30) by NASA.

“Webb's tools are designed to find and understand the first galaxies. In the first year of observations as part of JADES, we found several hundred candidate galaxies from the first 650 million years after the Big Bang.

According to them, early last year, a galaxy was discovered among the data that seemed to exceed the redshift by a factor of 14, which angered astronomers. “However, there were some features of this galaxy that made us wary. The galaxy was surprisingly bright, which was not expected for a galaxy so far away, and it was very close to another, making it look as if the two were part of a larger body.”

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When this galaxy was observed again in October 2023, using new imaging data obtained with Webb's narrower NIRCam (near infrared camera) filters, it became clear that it was of high redshift. “We knew we needed a spectrum to understand it better, as any information would be of great scientific interest, whether as a new milestone in Webb's investigations into the early universe or as a patchwork of a middle-aged galaxy.”

In January this year, NIRSpec observed the JADES-GS-z14-0 galaxy for about ten hours. According to Cargnani and Heinlein, when the spectrum was first processed, there was unambiguous evidence that the galaxy was already at a redshift of 14.32, breaking the previous record for the most distant galaxies. Seeing this spectrum was exciting for the entire team, given the mystery surrounding this source.

Scientists used the James Webb Space Telescope's NIRSpec to obtain a spectrum of the distant galaxy JADES-GS-z14-0 in order to precisely measure its redshift and thus its age. This galaxy dates back less than 300 million years after the Big Bang. Image credit: NASA, ESA, CSA, Joseph Olmstead (STScI). Science: S. carniani (Scuola Normale Superiore), JADES collaboration.

The amount of starlight impresses the team

“This discovery was not just a new distance record for our team,” the astronomers said. “The most important aspect of JADES-GS-z14-0 is that from this distance, we know that this galaxy must be very luminous at its core. From the images we discovered that it is more than 1,600 light-years across, proving that the light we see comes mainly from From young stars and not from nearby emissions from a growing supermassive black hole.

This amount of starlight indicates that the galaxy's mass is hundreds of millions more than the mass of the Sun. This begs the question: How could nature form such a bright, massive, and large galaxy in less than 300 million years?

The data reveals other important aspects of this amazing galaxy. It is noted that its color is not as blue as it could be, indicating that some of the light has been reddened by the dust, even at these very early times.

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JADES researcher Jake Helton of Steward Observatory and the University of Arizona also determined that the JADES-GS-z14-0 galaxy was detected at longer wavelengths using the Webb mid-infrared (MIRI) instrument, which is remarkable considering its distance.

MIRI observation covers wavelengths of light emitted in the visible light range that are red-shifted outside the range of Webb's near-infrared instruments. Hilton's analysis indicates that the brightness of the source observed by MIRI is higher than what would be expected from measurements from other Webb instruments, indicating the presence of strong emission of ionized gas into the galaxy in the form of bright hydrogen and oxygen emission lines. “The presence of oxygen so early in the life of this galaxy is a surprise and indicates that several generations of very massive stars already lived and died before we observed the galaxy,” the scientist said.

These observations show that JADES-GS-z14-0 does not resemble the types of galaxies whose existence in the early universe has been predicted by theoretical models and computer simulations.

“Given the observed brightness of the source, we can predict how it will grow over cosmic time, and so far we have not found any suitable analogue for the hundreds of other galaxies we have observed at high redshift in our research,” Cargnani revealed.

Based on the relatively small area of ​​sky surveyed to find JADES-GS-z14-0, its discovery has profound implications for the expected number of bright galaxies seen in the early universe.

It is likely that many of these bright galaxies will be discovered by Webb, perhaps at early times, within the next decade.

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