Two weeks after NASA revealed the first images taken by the JWST observatory, scientists woke to the news that cosmology might be broken. Analyzing the JWST’s images, a team of astronomers had spotted a galaxy that shouldn’t be there, at least according to the most frequently used model of the Universe’s evolution, called ΛCDM [1]. The galaxy was inexplicably bright and incredibly young with respect to the current age of the Universe. The initial calculations dated it to just 250 million years after the big bang, when there should not have been enough time for such a galaxy to have evolved. “There was a lot of press given to the idea that the JWST discoveries were a challenge for the basic paradigm of cosmology,” says Rachel Somerville, who studies galaxy formation at the Flatiron Institute, New York.
A flurry of reports of other early-Universe galaxies with anomalously high brightnesses then emerged, leaving astronomers on tenterhooks as to what they might see next [2]. “As more data came in, it became clear that the abundance of early bright galaxies was higher than theorists had predicted,” says Steven Finkelstein, an astrophysicist at the University of Texas at Austin. “It was an incredibly exciting time.”
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