Little Red Dots

Astronomers are racing to understand mysterious ancient objects that pepper images taken by the James Webb Space Telescope

- REBECCA BOYLE

WHEN ASTRONOMERS GLIMPSED the first images from the James Webb Space Telescope (JWST) in July 2022, they saw the kind of universe most of them have come to expect.

There were dazzling blue bursts of light, glowing trails of stardust, curtains of gas backlit by the birth of stars.

But things got weird very quickly. Almost every new image showed mysterious, tiny red points. The spots were extremely compact, very bright and distinctly red. There were so many of them. Everywhere JWST looked, the telescope found at least one specimen of what are now commonly called Little Red Dots (LRDs).

Astronomers quickly dated the dots to about 600 million years after the big bang, which means their light traveled almost the entire lifetime of the universe before arriving in JWST's honeycomblike hexagonal mirrors.

The dots were everywhere, until they were nowhere; about 1.5 billion years after the big bang, they mostly disappear.

The age, size and sheer number of the Little Red Dots all point to something new, something that JWST is uniquely capable of seeing. "They are in every single image the telescope takes," says Massachusetts Institute of Technology astrophysicist Rohan Naidu. “We have to find out about them if we want to tell a complete story about the early universe.”

At first, astrophysicists coalesced around a few theories to explain LRDs, each of which has implications for the evolution of the universe. Little Red Dots might be compact galaxies with brightly belching black holes at their centers. They could represent a never-before-seen stage of the black hole life cycle. They could be dusty starburst galaxies, exploding with new stellar populations like so many popcorn kernels encountering hot oil.