One of the surprising discoveries of the James Webb Space Telescope (JWST) is that galaxies formed very early in the Universe.
JWST has discovered about two dozen galaxies at a redshift of around z = 14, meaning that we see them at a time when the cosmos was just 300-500 million years old.
The most distant galaxy, JADES-GS-z14-0, is seen at an age of less than 300 million years.
All of these galaxies are rich with stars and have a basic structure similar to what we see in more modern galaxies. This discovery challenged our understanding of galactic evolution. Now a new discovery challenges it even further.
Soon after the Big Bang, the Universe was filled with just two elements: hydrogen and helium. There were small traces of other light elements such as lithium, but none of the heavier elements such as iron, carbon, or oxygen.
Those elements are formed through nuclear fusion in the cores of stars, so they didn’t appear in the Universe until the first generation of stars formed, lived their short lives, and died as supernovae.
So we would presume the earliest galaxies were filled with massive, brilliant hydrogen stars, surrounded by a diffuse nebula of hydrogen and helium. But observations from the Atacama Large Millimeter/submillimeter Array (ALMA) found the presence of oxygen in JADES-GS-z14-0.
The result is nothing more than stunning because it shows even galaxies little more than 100 million years old were already entering their main sequence of evolution.
It is as if we looked to the edge of the Universe expecting to see infants and finding teenagers.
Oxygen forms through a nuclear process known as the CNO cycle. It uses helium as a catalyst to create carbon, nitrogen, and oxygen. The observations detected oxygen at such a strong level that we know JADES-GS-z14-0 had enough heavier elements to start forming the second generation of stars.
Stars more like the Sun, or even red dwarfs, which can’t form just from hydrogen and helium. The presence of these elements also suggests that early planet formation could be occurring within the galaxy.
The detection of oxygen also means we can confirm JADES-GS-z14-0 is not simply a closer galaxy that appears more distant. Oxygen emission lines allow us to pinpoint its redshift to z = 14.1796 ± 0.0007.
It’s even younger than we thought, and it already has 10 times more heavy elements than we would expect.
Within less than 300 million years, the Universe was forming a diverse array of stars and had the elements necessary to form the building blocks of life.
Written by Brian Koberlein/Universe Today.
