JWST Finds Oldest Quasar Pair Yet — and It Shouldn't Exist

Quasars in the nearby universe aren't a puzzle. Compact pairs of them are simply rare. Galaxy mergers, which drag their central black holes together, happen constantly, so tight pairs should be everywhere. Three things hide them: the quasar phase is short on cosmic timescales, distant pairs are faint for ground-based telescopes, and the two members blur together at great distances.

The real trouble starts before the universe turned 1 billion years old. Standard models say black holes need at least 1 billion years to feed and merge their way to millions or billions of solar masses. Yet since it began operating in 2022, JWST has routinely found quasars as early as 400 million years after the Big Bang.

"We observed Nāpōwawāʻenakaulua at a time when the universe was only a thirteenth of its age and, astonishingly, its supermassive black holes are just as massive as those we see today," Onorato said.

This is only the third quasar pair ever found at Cosmic Dawn, and it piles pressure on existing models of black hole growth.

How was it found?

The discovery came from JWST's Aether survey, a census of early-universe objects. Using the telescope's NIRSpec instrument — a near-infrared spectrograph that splits light to reveal an object's properties — Aether has uncovered 200 quasars, just under half of all known early-universe quasars.

While browsing that dataset, the team realized the quasar J1602+4228A wasn't alone. It had a companion, now catalogued as J1602+4228B. Splitting the two from the ground should have been nearly impossible. Gemini North managed it thanks to perfect timing and clear skies over Maunakea, the dormant volcano that hosts the telescope.

What comes next?

The object remains a mystery, but a useful one. It gives astronomers a rare window onto how galaxies assembled during Cosmic Dawn, a pivotal stage in cosmic evolution.

"Nāpōwawāʻenakaulua is a really unique environment," Onorato said. "It's a laboratory for astronomers to study how the very first massive galaxies and their central black holes assembled together through direct galaxy interactions during these early times."

The findings, while peer-reviewed, describe a single system, and preliminary interpretation of a small sample — three Cosmic Dawn pairs — so conclusions about black hole growth models may shift as more data arrives. The team published its results on Nov. 10 in The Astrophysical Journal Letters.

The bottom line: the universe's first supermassive black holes keep showing up too early and too big, and this record-setting pair is the sharpest challenge yet to how we think they grew.