Astronomers have made a groundbreaking discovery with the NASA/ESA James Webb Space Telescope (JWST) by observing a galaxy from 700 million years after the Big Bang that is growing from the inside out.
This early universe galaxy, although 100 times smaller than our Milky Way, is surprisingly mature for its age and is rapidly forming new stars, especially in its outer regions.
The findings provide new insights into how galaxies evolved during the early stages of the universe.
The galaxy, studied by researchers at the University of Cambridge, has a dense core filled with stars, much like the center of a big city.
However, in the “suburbs” of the galaxy, star formation is increasing, causing the galaxy to expand outward.
This process, known as “inside-out” growth, is the earliest observation of such galaxy development.
Until now, it was impossible to study galaxies at such an early stage of the universe’s history.
This research, published in Nature Astronomy, offers valuable clues about how galaxies transform from gas clouds into complex structures like those we see today.
Dr. Sandro Tacchella, co-lead author from Cambridge’s Cavendish Laboratory, explains, “We’ve had lots of data for more recent galaxies, but with Webb, we can now look billions of years into the past and explore the first billion years of cosmic history.”
There are two main ways galaxies grow: by pulling in gas to form new stars or by merging with smaller galaxies.
However, it’s unclear if these same processes occurred in the early universe. The discovery of inside-out growth gives scientists new insights into how galaxies might have evolved during this distant time.
Tacchella compares the growth of a galaxy to a spinning figure skater: “As the galaxy pulls in gas from larger distances, it spins faster and faster, forming spiral or disk shapes.” This particular galaxy, observed as part of the JADES (JWST Advanced Extragalactic Survey) collaboration, shows most of its star formation happening in the outer regions, while its dense core is similar to much larger galaxies seen today.
Using data from the JWST, the researchers analyzed the light from the galaxy at different wavelengths. This helped them determine the age and mass of the stars, revealing that the core contains older stars while the outer regions are still actively forming new ones.
The galaxy is doubling its mass in the outskirts every 10 million years, a rate much faster than the Milky Way, which takes 10 billion years to double its mass.
The study is an exciting step toward understanding how galaxies like this one grew in the early universe. As Tacchella points out, “This is just one galaxy, but by studying more, we may be able to uncover the growth patterns of galaxies and understand how they evolve over time.”
