The James Webb Space Telescope (JWST) has found a galaxy in the early universe so massive it shouldn’t exist, posing a “significant challenge” to the standard model of cosmology, according to the study’s authors.
What do you need to know:
- The galaxy, called ZF-UDS-7329, contains more stars than the Milky Way, despite having formed just 800 million years into the universe’s 13.8 billion-year lifespan.
- This means that they were somehow born without dark matter driving their formation, contrary to what the standard model of galaxy formation suggests.
- How this could have happened is still unclear, but like previous discoveries of other inexplicably massive galaxies in the early universe, JWST threatens to revolutionize our understanding of how the universe’s first matter formed, or even the Standard Model of cosmology itself.
- The researchers published their findings on February 14 in the journal Nature.
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Discovery
“Having these extremely massive galaxies so early in the universe poses significant challenges to our standard model of cosmology,” Claudia Lagos, study co-author and associate professor of astronomy at the International Center for Radio Astronomy, said in a statement. That’s because the massive structures of dark matter, thought to be necessary components for holding the first galaxies together, haven’t had time to form so early in the universe, Lagos added.
Light travels at a fixed speed through the vacuum of space, so the deeper we look into space, the more distant light we catch and the further back in time we see. This allowed researchers to use JWST to detect ZF-UDS-7329 around 11.5 billion years ago.
By studying the spectra of light coming from the stars in this extremely distant galaxy, the researchers found that the stars were born 1.5 billion years before this observation, or about 13 billion years ago.
Astronomers aren’t sure when the first clusters of stars began to group together into the galaxies we see today, but cosmologists previously estimated that the process began slowly during the first few hundred million years after the Big Bang.
A challenge to current theories
Current theories suggest that halos of dark matter (the mysterious, invisible substance thought to make up 25% of the current universe) merged with gas to form the first galaxy seeds. After 1 billion to 2 billion years of the universe’s life, the early protogalaxies reached puberty, forming into dwarf galaxies that began eating each other up to grow into galaxies like ours.
But a new discovery confounded that view: Not only did the galaxy crystallize without enough dark matter to seed it, but soon after the sudden burst of star formation, the galaxy suddenly went quiet—that is, its star formation stopped.
This pushes the limits of our current understanding of how galaxies form and evolve. A key question now is how they form so quickly in the early universe, and what mysterious mechanisms cause star formation to suddenly stop when the rest of the universe does.
Themiya Nanayakkara, co-author of the study and an astronomer at Swinburne University of Technology in Australia, said in a statement
The researchers’ next steps will be to look for other galaxies like this one. If they find any, it could seriously contradict previous ideas about how galaxies formed, they said.
