Early galaxies weren't mystifyingly massive after all, James Webb Space Telescope finds

Black holes may be behind why the newborn universe appeared to possess more huge galaxies than scientists could explain, a new study finds.

Astronomers made this discovery with the help of NASA's James Webb Space Telescope (JWST), the largest and most powerful off-Earth observatory to date. Launched in December 2021, the $10 billion JWST specializes in detecting infrared light, just like thermal vision goggles.

Scientists are using JWST to investigate the early cosmos. The universe has expanded greatly since it was born about 13.8 billion years ago in the Big Bang, and that means the light from early galaxies appears reddened by the time it reaches Earth, much as how an ambulance siren sounds lower-pitched to people as the vehicle drives away. JWST is designed to help capture light from the earliest galaxies, much of which has shifted into the infrared range.

When astronomers got their first glimpses of galaxies in the early universe from JWST, they were expecting miniature versions of modern galaxies. Instead, they found that some galaxies had grown very large very quickly.

Related: Is the James Webb Space Telescope really 'breaking' cosmology?

This previous research suggested that something might be wrong with scientists' thinking about what the universe is made of and how it has evolved since the Big Bang, known as the standard model of cosmology. All in all, early galaxies seemed to be larger than what the standard model expected by "roughly a factor of two," study co-author Steve Finkelstein, an astrophysicist at the University of Texas at Austin, told Space.com.

Now, Finkelstein and his colleagues find that some of these early galaxies are actually much less massive than they first appeared. They detailed their findings online Aug. 26 in The Astrophysical Journal.