James Webb space telescope discovers galaxies forming after the Big Bang
After the Big Bang, the first galaxies first had to make the universe translucent. Three galaxies have now been discovered that were formed during this epoch.
Artistic representation of emerging galaxies in the early universe.
(Image: NASA, ESA, CSA, Joseph Olmsted (STScI))
For the first time in the history of astronomy, the James Webb Space Telescope has succeeded in observing the formation of early galaxies more than 13.3 billion years ago. This has now been published by a research team led by Kasper Elm Heintz from the University of Copenhagen. The astrophysicist describes the light now analyzed as coming from "sparkling islands in a sea of otherwise neutral, opaque gas". The space telescope therefore sees their formation during the epoch of so-called reionization when the earliest galaxies made the universe translucent. However, while galaxies were found there at a later stage of development, the formation of the three can be seen "live", so to speak.
Formation in a largely opaque universe
The space telescope only sees the three galaxies as "subtle red spots", explains NASA. But spectral studies have shown that parts of the light were absorbed by large quantities of neutral hydrogen gas. This must be very widespread in the galaxy and obscure a large part of it. This finding suggests that we are in a sense watching this neutral gas coalesce in galaxies, where it cools, clumps together and forms new stars, explains co-author Darach Watson. The team has already requested more observation time to find out exactly where this gas is in the galaxies and exactly how pristine it is.
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During reionization, around 500 to 900 million years after the Big Bang, the translucent universe we know today was created. During this "cosmic dawn", the first stars and galaxies separated the electrons from the hydrogen nuclei (the protons). These could then no longer absorb photons (i.e. light) and the universe became transparent. The James Webb Space Telescope has already determined that the main part of this reionization was carried out by comparatively small dwarf galaxies, which acted like cosmic lighthouses. It was previously unclear which structures provided the necessary radiation, and supermassive black holes or large galaxies had also been considered.
The three galaxies that have now been discovered, which are currently being formed during this epoch, can be seen in a state that they were in around 400 to 600 million years after the Big Bang, explains NASA. At that time, such galaxies were not isolated ecosystems, but closely connected to intergalactic structures of pristine gas, explains co-author Simone Nielsen. Before the James Webb Space Telescope was put into operation, it was not possible to take or collect images and spectral data for this epoch, the team explains. They have now published their research in the scientific journal Science.
(mho)
