the crack of It would take some time for cosmology to emerge. But when the James Webb Space Telescope (JWST) opened its lenses last spring, a very distant but very bright galaxy immediately popped into the telescope’s field of view. “They were very bright and outstanding,” said Rohan Naidu, an astronomer at the Massachusetts Institute of Technology.
The galaxy’s apparent distance from Earth suggests that it formed much earlier in the history of the universe than anyone expected. Questions swirled, but in December, astronomers confirmed that some galaxies are actually as distant and therefore primitive as they appear. The earliest of these confirmed galaxies, he glowed 330 million years after the Big Bang, becoming a new record holder for the earliest known structure in the universe. That galaxy was fairly dim, but other candidates loosely associated around the same time were already bright.
How could a star ignite in a cloud of superheated gas just after the Big Bang? How could it have been hastily woven into a gigantic, gravitationally bound structure? Finding an early galaxy seems like finding a fossilized rabbit in Precambrian strata. “There’s nothing big early on. It takes time to get to the big things,” says Mike He Boylan His Colchin, a theoretical physicist at the University of Texas at Austin.
Astronomers began to wonder if the early big-thing outbreaks were at odds with our current understanding of the universe. Some researchers and media outlets have claimed that telescopic observations have violated the standard model of cosmology (a well-tested set of equations called the Lambda Cold Dark Matter (ΛCDM) model), suggesting a new cosmic component. and provocatively pointed out the governing law. However, it has since become apparent that the ΛCDM model is resilient. Instead of forcing researchers to rewrite the rules of cosmology, the JWST findings are making astronomers rethink how galaxies were created, especially at the beginning of the universe. Telescopes haven’t yet broken cosmology, but that doesn’t mean that the too early galaxy case will turn out to be anything but groundbreaking.
simple times
To understand why the detection of very early bright galaxies is so amazing, it helps to understand what cosmologists know or think they know about the universe.
After the Big Bang, the universe of infancy began to cool. Within millions of years, the swirling plasma that filled the universe settled down, and electrons, protons, and neutrons combined into atoms, mostly neutral hydrogen. Things were quiet and dark. Then something happened.
Most of the matter scattered after the Big Bang is made up of invisible matter called dark matter. It had a powerful effect on the universe. Especially at first. In a standard image, cold dark matter—a term for invisible, slow-moving particles—splattered indiscriminately into space. In some areas its distribution was more dense, and in these areas it began to collapse and clump together. As the atoms also cooled, they eventually condensed, giving birth to the first stars. These new radioactive sources recharged the neutral hydrogen that filled the universe during the so-called reionization epoch. Gravity has caused larger and more complex structures to grow, building the vast cosmic web of the galaxy.
