Astronomers discover Nāpōwawāʻenakaulua, the oldest compact quasar pair in universe

An international team of astronomers discovered the most distant — and thus the oldest — compact pair of quasars ever found in the universe.

Officially named J1602+4228AB, the quasars — which are pairs of black holes that become so bright they outshine all the stars in their host galaxy — also are the most compact pair found at cosmic dawn, what astronomers call the early universe era, because of their close separation.

The surprising nature of the pair was revealed through observations with the Gemini North telescope atop Mauna Kea on the Big Island and James Webb Space Telescope.

They are separated by about 18,100 light-years, or roughly one-fifth the diameter of the Milky Way galaxy, and have have masses of 1.5 billion and 400 million times that of our sun, respectively. Their distance from Earth places them at only 900 million years after the Big Bang.

The universe’s first stars, galaxies and black holes were still relatively young during that period, so the extreme mass of the quasars — given the Hawaiian nickname Nāpōwawāʻenakaulua — challenges current understanding about how large-scale cosmic structures are formed.

Nāpōwawāʻenakaulua translates to “two celestial bodies of fathomless powerful darkness in the brilliance of heat reincarnating energy into the universe,” and was created by the A Hua He Inoa program at ʻImiloa Astronomy Center of Hawaiʻi and University of Hawai‘i’s Ka Haka ʻUla O Keʻelikōlani Hawaiian Language College in Hilo on Hawaiʻi Island.

Astronomers theorize quasar pairs are common in the universe; however, actually finding and characterizing them is rare. Even rarer — finding them this early in the history of the universe.

Silvia Onorato, a postdoctoral research associate at U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory, led the study. The results are presented in a paper recently published in The Astrophysical Journal Letters.

“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,” says Onorato. “We observed Nāpōwawāʻenakaulua at a time when the universe was only a 13th of its age and, astonishingly, its supermassive black holes are just as massive as those we see today.”

The first billion years of cosmic time represent a period of furious assembly.

Dark matter halos collapsed, galaxies ignited their first generation of stars and massive galaxies formed the very first supermassive black holes at their centers. As galaxies interacted, collided and, in some cases, merged completely, their supermassive black holes were fed with large quantities of gas and stars.

A fraction of this “accreted mass” from feeding was converted into energy, causing the black holes to become quasars.

Scientists established galaxy interactions and mergers are common; they expect to find an abundance of quasar pairs with a separation less than the typical size of a galaxy. However, this proves difficult for a few reasons:

• A supermassive black hole’s “quasar phase” is relatively short.
• These objects are very far away, so they are faint and hard to detect with ground-based telescopes.
• At such small separation scales, individual members of a quasar pair are hard to resolve.

Enter Nāpōwawāʻenakaulua, which is not only the third known quasar pair found at cosmic dawn but found so early in the history of the universe that scientists cannot explain how it came into existence.

Nāpōwawāʻenakaulua was uncovered in data from the Aether survey — a James Webb Space Telescope program led by Emanuele Paolo Farina, associate scientist at Gemini — aimed at compiling a census of objects in the early universe.

Using the space telescope’s near-infrared spectrograph integral field unit, the survey collected a sample of 200 quasars representing 43% of all known quasars at this stage of cosmic history. It was during visual inspections of the Aether dataset that the team made the exciting discovery that quasar J1602+4228A had a companion.

Follow-up observations with Gemini North’s near-infrared spectrograph allowed the team to resolve the two quasars as individuals. J1602+4228A and B are so close and J1602+4228B is so faint that observing it from the ground should have been nearly impossible.

It was perfect timing and perfect weather conditions on Mauna Kea that allowed the team to accomplish this feat.

“The sky over Mauna Kea was so clean and sharp that we managed to collect the data in only 2 nights,” said Onorato.

Additional observations with Gemini’s multi-object spectrograph further constrained the properties of the quasar pair.

While the complete origin Nāpōwawāʻenakaulua remains a mystery, the team proposes this rare quasar pair could serve as a signpost of an extreme peak in the matter density field of the early universe, where galactic interactions simultaneously fed star formation and rapid growth of black holes.

“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.”