Close quasar pair at cosmic dawn challenges models of black hole growth

Astronomers have identified a tight pair of quasars, J1602+4228AB, as they appeared only 900 million years after the Big Bang. The two supermassive black holes are already very massive, and the team reports that current theory cannot explain how even one such object, let alone two, grew so large so quickly. The study, led by Silvia Onorato of NSF NOIRLab, appears in The Astrophysical Journal Letters.

A rare find from the early universe

Quasars are black holes that shine fiercely as they swallow gas, often outshining every star in their host galaxy. Galaxy mergers are common, so researchers expect many quasars to occur in close pairs within a single galaxy-sized region. Such pairs are hard to catch. A quasar phase is relatively brief, distant sources are faint, and at small separations the two members blur together in most telescope images.

This system, nicknamed Nāpōwawāʻenakaulua, is only the third quasar pair known from cosmic dawn, the early era when the first galaxies and black holes were assembling. The two objects are about 18,100 light-years apart, roughly one-fifth the diameter of the Milky Way. That makes it the tightest quasar pair yet found from this period. The name was devised through the A Hua He Inoa programme at the ʻImiloa Astronomy Center of Hawaiʻi and the University of Hawaiʻi's Hawaiian Language College.

How the pair was found

The discovery came from the Aether survey, a James Webb Space Telescope (JWST) programme led by Emanuele Paolo Farina of NSF NOIRLab and Gemini. Aether is building a census of early-universe quasars. Using the Near-Infrared Spectrograph's integral field unit, it gathered a sample of 200 quasars, which the team says is 43% of all those known at this stage of cosmic history.

While inspecting the survey data by eye, the researchers noticed that quasar J1602+4228A had a companion. Follow-up spectroscopy with the Gemini Near-Infrared Spectrograph on Gemini North, on Maunakea, separated the two sources. The companion, J1602+4228B, is faint and lies very close to its neighbour, so detecting it from the ground should have been close to impossible. According to Onorato, unusually clear skies meant the data were collected in just two nights. Further observations with the Gemini Multi-Object Spectrograph helped to pin down the properties of the pair.

A growth puzzle

The black holes have estimated masses of 1.5 billion and 400 million times that of the Sun. At an epoch when the first stars, galaxies and black holes were still young, such masses are difficult to reconcile with standard models of structure formation. Onorato notes that these black holes are as massive as those seen in the present-day universe.

The team does not claim to have resolved the question. Their working suggestion is that the pair marks an extreme peak in the matter density of the early universe. In such a region, interactions between galaxies could have driven star formation and rapid black hole growth together.

Why it matters

The system offers a rare chance to study how massive galaxies and their central black holes assembled through direct galaxy interactions so soon after the Big Bang. It also gives theorists a concrete test case. Models of early black hole seeding and growth will need to account for two massive, actively accreting black holes in close proximity at this epoch.

The source describes the discovery and its proposed interpretation but does not report further observations planned for the system. Detailed spectroscopy of the host environment, and searches for other close pairs in Aether-type data, would help show whether Nāpōwawāʻenakaulua is a freak case or part of a wider population.

Source: Earliest known compact quasar pair poses a black hole growth puzzle (Phys.org, 11 November 2026).

Image: AI-generated illustration.