Alex McColgan

But if they only contain stars, the galaxies are too compact to contain all of them, reaching stellar densities that are unthinkable.

So if little red dots are not young galaxies of hot stars, and they're not black holes, what could they be?

Is it possible we've stumbled upon an entirely new type of cosmic object, one unlike anything we've ever seen before?

This was exactly the question Anna de Graaf and her team set out to answer.

De Graaf is an astrophysicist at the Centre for Astrophysics, Harvard and Smithsonian, with a particular interest in the most extreme objects in the early universe, the things that sit furthest outside the expected distributions.

So, she designed a survey to go after them directly.

The Red Unknown's Bright Infrared Extracalactic survey was a deliberate hunt for the reddest, brightest, rarest objects in the sky.

During 2024, the graph's team spent nearly 60 hours of web time obtaining spectra for 300 red sources, of which they think 30 to 50 were the mysterious little red dots.

This made it the largest ever spectroscopic sample of these dots at its time of publication in March 2025.

The objects ranged in age from 650 million to 1.5 billion years after the Big Bang.

But while she hoped her survey would bring calm clarity and definitive answers to the field, it did of course the exact opposite.

Rubies revealed that these bright red objects are far more diverse than anyone initially imagined.

Even though they seemed similar when imaged, spectroscopic data showed they were actually several different types of objects, such as dusty galaxies still forming stars,

other galaxies that may have stopped forming stars surprisingly early, and active black holes powering galactic nuclei.

It seemed no matter which side of the starburst galaxy versus black hole debate you were on, you were, harshly, right.

But within that sample, there was a subset that didn't fit any of these categories.

Objects with the V-shaped spectra, the broad emission lines, the point source morphology, all the signatures that had resisted explanation from the beginning.

And then, in July 2024, the team stumbled upon a little red dot 11.9 billion light years away with a spectrum so extreme it stopped them in their tracks.

They called it the cliff.

To understand why the cliff was so important, you need to understand what the bomber breaks we saw earlier are really telling you.