Katherine Whitaker was on a video call with colleagues last summer when NASA released the first pictures from the ultra-powerful James Webb Space Telescope (JWST). Among the many awe-inspiring images was one of a sliver of sky surrounding the galaxy cluster SMACS 0723: It was brimming with some of the oldest and most distant galaxies ever recorded. “We would zoom in and be like, ‘Oh wow,’ and ‘What the heck is that?’” recalls Whitaker, an astronomer at the University of Massachusetts Amherst. “It was joy—pure joy.”
That thrill was merely a taste of what was to come. In just its first year of scientific operations, the $10-billion infrared telescope has delivered stunning views of the nascent universe, finding large numbers of surprisingly bright galaxies that existed at a time when the cosmos was in its infancy. With its 6.5-meter mirror, JWST was designed to investigate this early era, which was mostly out of reach for its predecessor, the 2.4-meter Hubble space telescope (HST). Observations thus far have astonished researchers and left them trying to digest exactly what they’re seeing.
According to the standard model of cosmology, after the fiery Big Bang 13.8 billion years ago, the universe cooled, and energy turned into matter that eventually coalesced during the first few hundred million years, forming the first generation of stars and galaxies. Astronomers thought they had a decent understanding of this process.
But JWST’s initial results may suggest that stars and galaxies were forming far faster than anyone expected. The telescope had done nothing less, read the headlines, than “break the universe” and upend models of cosmic history. Subsequent data have ruled out some of the more dramatic findings, and new simulations can accommodate at least a few of the strange observations. But some bright, massive, and early galaxies continue to confound theorists, suggesting that our understanding could shift in the coming years. “No data at the moment has broken the universe,” says Priyamvada Natarajan, a theoretical astrophysicist at Yale University in New Haven, Connecticut. “But I think there are interesting potential tensions emerging on different scales.” [Continue reading…]