The search is on for some of the flimsiest lumps of matter and energy ever dreamed up by physicists. They are darker than night, barely more substantial than a thought, and named after a laundry detergent. But axions, as they are called, could constitute most of the matter in our universe, forming the unseen skeletons of galaxies and chains of light that adorn the skies of astronomers. Confirmation of their existence would upset some of the deepest theories of nature.
“For nearly 10 years we’ve been operating in a search mode, and any day we could make a discovery,” said Gray Rybka, a physicist at the University of Washington who is a spokesman for the Axion Dark Matter eXperiment, or ADMX, in Seattle, which is trying to conjure axions with powerful magnetic fields.
Astronomers, too, are hunting for hints that axions exist, by analyzing how black holes spin and the shapes of infant galaxies that the James Webb Space Telescope has brought to light. But so far, nobody has found them.
Success would provide a big clue to one of the grandest mysteries in the cosmos: What is the universe made of?
Signs From the Sky
Astronomers tracking the motions of stars and galaxies have reluctantly concluded that there is much more to the universe than can be seen directly with telescopes. The ordinary matter that composes the stars, planets, galaxies and us accounts for only one-sixth of the matter in the universe. The rest is so-called dark matter, invisible and aloof but with sufficient gravity to hold the visible universe together.
Countless particles have been hypothesized as candidates for dark matter. But the most popular are those that fill gaps in the Standard Model, humanity’s best, if imperfect, model of nature and the forces that drive it.