April 24, 2024

Webb reveals the giant of the early universe


Ancient Galaxy Concept Art

Recent observations from the James Webb Space Telescope have discovered Gz9p3, an ancient galaxy from the early years of the Universe, revealing it to be exceptionally massive and mature. This discovery, which indicates rapid star formation and the first galaxy mergers, is leading astrophysicists to review their models of the evolution of the early Universe. (Artist’s concept.) Credit: SciTechDaily.com

Detailed images of one of the first galaxies show that growth in the early Universe was much faster than previously thought.

Astronomers are currently enjoying a fruitful period of discovery, investigating the many mysteries of the early Universe.

The successful launch of the James Webb Space Telescope (JWST), a successor to NASA’s Hubble Space Telescope, has pushed the limit of what we can see.

Observations are now going into the first 500 million years after the Big Bang, when the Universe was less than five percent of its current age. For humans, this time would place the Universe firmly in the infant phase.

However, the galaxies we observe are certainly not infants, with new observations revealing galaxies more massive and mature than previously expected for such ancient times, helping to rewrite our understanding of galaxy formation and evolution.

Our international research team recently made unprecedentedly detailed observations of one of the first known galaxies – dubbed Gz9p3, and now published in Nature Astronomy.

Its name comes from the Glass collaboration (the name of our international research team) and the fact that the galaxy is at a redshift of z=9.3, where redshift is a way of describing the distance to an object – hence G and z9p3.

Gz9p3 JWST

Gz9p3, the brightest known merging galaxy from the first 500 million years of the Universe (observed using JWST) Left: Direct image shows a double nucleus in the central region. Right: The contours of the light profile reveal an elongated, irregular structure produced by the merger of galaxies. Credit: NASA

Just a few years ago, Gz9p3 appeared as a single point of light across the NASA's James Webb Space Telescope Multilayer Sunshield

The James Webb Telescope — the largest and most powerful device of its kind ever launched into space — uses a 6.5-meter primary mirror made of 18 hexagonal mirrors coated with a gold coating to produce some of the first images of the Universe. Credit: NASA GSFC/CIL/Adriana Manrique Gutierrez

Next, our study went deeper, to describe the population of stars that make up the merging galaxies. Using JWST, we were able to examine the galaxy’s spectrum, splitting the light in the same way a prism splits white light into a rainbow.

When using only images, most studies of these very distant objects show only very young stars because younger stars are brighter and therefore their light dominates the image data.

For example, a young, bright population caused by the merger of galaxies, less than a few million years old, overshadows an older population, already more than 100 million years old.

Using the spectroscopy technique we can produce observations so detailed that the two populations can be distinguished.

New models of the early universe

Such a mature and elderly population was not predicted, considering how early stars would have to have formed to have aged enough in this cosmic epoch. Spectroscopy is so detailed that we can see subtle features of ancient stars that tell us there’s more there than we think.

Specific elements detected in the spectrum (including silicon, carbon and iron) reveal that this older population must exist to enrich the galaxy with an abundance of chemicals.

It is not only the size of the galaxies that is surprising, but also the speed at which they grew to a chemically mature state.

These observations provide evidence of a rapid and efficient accumulation of stars and metals shortly after the Big Bang, linked to ongoing galaxy mergers, demonstrating that massive galaxies with several billion stars existed earlier than expected.

Hubble Abell 2744 boundary field

The observations provide evidence of a rapid and efficient accumulation of stars and metals shortly after the Big Bang. Credit: NASA, ESA, Jennifer Lotz (STScI), Matt Mountain (STScI), Anton M. Koekemoer (STScI), HFF Team (STScI)

Isolated galaxies increase their star population on site from their finite reservoirs of gas, however, this may be a slow way for galaxies to grow.

Interactions between galaxies can attract new influxes of pure gas, providing fuel for rapid star formation, and mergers provide an even more accelerated channel for mass accumulation and growth.

All of the largest galaxies in our modern Universe have a history of mergers, including our own.

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