Webb found two giant black holes side by side 900 million years after the Big Bang

The James Webb Space Telescope has found two supermassive black holes feeding side by side when the universe was less than a billion years old. They form the oldest compact pair of quasars ever identified, and their separation is shorter than the distance between our Sun and the center of the Milky Way.

The pair matters because nobody expected to catch one so early. The two black holes are each hundreds of millions to billions of times heavier than the Sun, and the chance of finding two of them this close together at that epoch is far higher than current models of the young universe predict.

The system is officially called J1602+4228AB. Its Hawaiian name, Nāpōwawāʻenakaulua, was created by Larry Kimura of the University of Hawaiʻi’s Hawaiian language college through the A Hua He Inoa naming program. It translates as “Two celestial bodies of fathomless powerful darkness in the brilliance of heat reincarnating energy into the Universe.” The study, led by Silvia Onorato of NSF NOIRLab, appears in The Astrophysical Journal Letters.

The light we see left the pair about 900 million years after the Big Bang. The larger black hole weighs about 1.5 billion times the mass of the Sun and the smaller one about 400 million. They sit roughly 18,100 light-years apart, about one fifth of the diameter of the Milky Way.

A quasar is a supermassive black hole that is swallowing so much gas that the matter around it outshines every star in its host galaxy. Both members of this pair are feeding at or slightly above the Eddington limit, the rate at which the radiation pushing outward from the hot gas balances the gravity pulling the gas inward. Both black holes are therefore growing about as fast as physics normally allows.

“There is no definitive theoretical explanation for how a single one of these giant quasars exists so early in the age of our Universe, much less two,” Onorato said in the NOIRLab announcement.

How Webb and Gemini found the second quasar

The pair turned up in the Aether survey, a Webb program led by Emanuele Paolo Farina of NSF NOIRLab and the International Gemini Observatory. The survey points Webb’s Near-Infrared Spectrograph at 200 quasars from the first billion years, about 43 percent of all known quasars from that period. Instead of a single spectrum, the instrument records a separate spectrum for every small patch of sky around each target.

During a visual check of every data cube, the team noticed that the known quasar J1602+4228 had a faint companion at almost exactly the same distance. Out of the 199 survey fields searched, it is the only companion quasar with broad emission lines, the signature of fast-moving gas close to a black hole. Webb observed this field for about 45 minutes.

The companion is roughly 19 times fainter than the main quasar, and the two are separated on the sky by just under one arcsecond, about the width of a coin seen from four kilometers away. To confirm it as a separate object, the team turned to the Gemini Near-Infrared Spectrograph on the Gemini North telescope on Maunakea in Hawaiʻi, and placed the slit so that it covered both quasars at once. The faint quasar received more than three hours of exposure. “The sky over Maunakea was so clean and sharp that we managed to collect the data in only two nights,” Onorato said. A third instrument, the Gemini Multi-Object Spectrograph, added optical light from the faint companion.

The redshifts of the two quasars, a measure of how much the expansion of the universe has stretched their light, differ by only about 15 kilometers per second, which places them at essentially the same distance from Earth.

How close is close for black holes this old

This is only the third quasar pair found at cosmic dawn, the era of the first galaxies, and it is the tightest. The previous most compact early pair, J2037-4537, has a separation of about 24,000 light-years and was seen roughly 100 million years later in cosmic history. Another candidate at a similar epoch, J1215-0148, is about 39,000 light-years wide, and astronomers still debate whether it is a real pair.

For scale, the Sun is about 26,000 light-years from Sagittarius A*, the black hole at the center of our galaxy. Sagittarius A* weighs about four million Suns. The larger black hole in this pair is roughly 380 times heavier, and it reached that mass when the universe was about 6.5 percent of its current age.

The team also asked how often a pair like this should turn up. Measurements of how quasars cluster on large scales, extended down to the scale of this pair, predict far fewer such neighbors than one in 199 fields. The observed pair sits 100 to 1,000 times above those extrapolations, even when the team used a fainter brightness threshold.

What the pair does not settle yet

The first open question is whether these are really two quasars. A galaxy sitting between us and a single distant quasar can bend its light and produce two images of the same object, an effect called gravitational lensing. The spectra argue against that. The two quasars differ in the slope of their light and in how much dust dims them, and the fast-moving outflows of gas seen in their oxygen emission lines have different shapes, and lensing cannot change those shapes. The team therefore tentatively favors a real pair. Archival Hubble images, however, show a possible foreground galaxy near the fainter quasar. The authors write that spectra alone cannot rule out lensing, and a full lens model is still in preparation.

The second limit is the masses themselves. Black hole weights derived from a single spectrum carry a systematic uncertainty of roughly a factor of two, so the 1.5 billion and 400 million figures are estimates, not precise measurements.

The third limit concerns the excess. The clustering predictions were measured on much larger scales and have to be extended far below their tested range, where the authors say theory is extremely uncertain. One pair cannot show whether such systems are common or whether this one is a rare coincidence.

Individually, the black holes break no rule: their masses and feeding rates match solitary quasars from the same era. What remains unexplained is how any black hole grew to a billion Suns so quickly, and why two of them did it so close together.

Why a merger may explain the pair

The team proposes that Nāpōwawāʻenakaulua marks an extreme peak in the density of matter in the early universe, a place where colliding galaxies pushed large amounts of gas toward their centers. That gas would fuel star formation and both black holes at the same time, which would explain why two quasars switched on together.

If the two host galaxies are merging, the black holes should eventually sink toward the center of the combined galaxy, form a bound pair and, in the far future, merge. Pairs like this are the early stage of the process thought to produce the faint background of gravitational waves reported by the NANOGrav collaboration.

Questions readers ask about the quasar pair

What is a quasar pair?

A quasar pair is two actively feeding supermassive black holes that sit close together in space, usually because their host galaxies are interacting or merging. Very few have been found in the first billion years after the Big Bang.

How far away is Nāpōwawāʻenakaulua?

Its light left the pair about 900 million years after the Big Bang, which corresponds to a redshift of about 6.08. The light has traveled for almost 13 billion years to reach Webb.

How do astronomers weigh a black hole this far away?

They measure the width of hydrogen emission lines from gas orbiting the black hole. Faster orbits mean broader lines, and combined with the brightness of the quasar, the width gives a mass estimate. These single-spectrum estimates are uncertain by about a factor of two.

Could the second quasar be an illusion caused by gravitational lensing?

It is possible but considered less likely. The two spectra differ in ways lensing should not produce, especially in the shapes of their gas outflows, but a candidate foreground galaxy has been spotted in Hubble images. A detailed lens model will test the idea.

What comes next

Webb recorded the discovery data on April 2, 2025, the Gemini follow-up continued into this year, and the paper was published on November 10, 2026. Onorato’s team is now preparing a dynamical study of the gas moving between the two quasars and a lens model based on archival Hubble images. A separate paper led by Roberto Decarli of Italy’s National Institute for Astrophysics will report the companion galaxies found across the whole Aether survey, the first step toward the statistical sample that can show whether pairs like this one are common or rare.

Reference: Onorato et al., “Nāpōwawā‘enakaulua: A Close Quasar Pair at Cosmic Dawn in the Aether Survey,” The Astrophysical Journal Letters, 2026. DOI: 10.3847/2041-8213/aeb11f

Tags: astronomy, James Webb Space Telescope, JWST, black holes, Gemini North, quasars