Newshot Webb Telescope Discovers the Oldest Quasar Pair Yet, and Existing Black Hole Growth Theories Struggle to Explain It
IT之家, November 15 news: Using the James Webb Space Telescope (JWST), astronomers have discovered the oldest pair of quasars powered by supermassive black holes observed to date. However, this discovery also poses a puzzle: according to existing theories, they should not have existed so early.
This closely adjacent pair of quasars was confirmed with the Gemini North telescope, designated J1602+4228AB, and nicknamed Nāpōwawāʻenakaulua. The name means “two celestial bodies in the endlessly powerful darkness that are reborn in heat and inject energy into the universe.”
What astronomers observed is how this quasar pair looked about 900 million years after the Big Bang. At that time, the universe was still in an extremely early stage. According to existing theories, supermassive black holes should not have had enough time to grow to such astonishing masses.
Nāpōwawāʻenakaulua is not only the oldest and most distant quasar pair discovered so far; the distance between the two supermassive black holes is also only about 18,100 light-years, roughly one-fifth of the diameter of the Milky Way. Their masses are about 1.5 billion and 400 million times that of the Sun, respectively.
This makes Nāpōwawāʻenakaulua the closest pair of quasars discovered in the cosmic dawn. The cosmic dawn is the earliest stage of the universe, when the first stars, galaxies, and black holes began to appear.
Research team leader Silvia Onorato of the U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory (NOIRLab) said in a statement: “There is currently no clear theory that can explain why such a giant quasar already existed so early in the universe, let alone two at the same time.”
“When we observed Nāpōwawāʻenakaulua, the universe was less than one-thirteenth of its current age. Astonishingly, the masses of these two supermassive black holes were already comparable to those of black holes observed today.”
How did supermassive black holes in the cosmic dawn obtain so much matter?
According to IT之家, quasars are among the brightest objects in the universe. A quasar can form when a supermassive black hole at the center of a large galaxy is surrounded by a flat, continuously rotating cloud of gas and dust. This mass of material is called an “accretion disk,” and the black hole continuously devours matter through the accretion disk.
The black hole's powerful gravity causes matter in the accretion disk to move at high speed and generate friction, which in turn releases a large amount of heat, making the accretion disk emit extremely bright light, whose brightness may even exceed the total of all stars in the surrounding galaxy. This intense light observed by astronomers is the quasar.
In the long history of about 13.8 billion years since the birth of the universe, discovering quasars is not particularly surprising. However, discovering two quasars so close together is still extremely rare.
In fact, such binary systems should not be rare in theory. Galaxies often merge, and the supermassive black holes at the centers of two galaxies will therefore gradually approach each other. This process should produce a large number of quasar pairs whose mutual distance is smaller than the typical size of a galaxy.
But astronomers face three major difficulties when searching for them.
First, the time during which a supermassive black hole is in the active quasar phase is relatively short on cosmic scales. Second, even if two quasars are relatively close, as long as they are in the extremely distant depths of the universe, they will appear very faint from ground-based observations and be difficult to detect. Finally, when two supermassive black holes are very close and at the same time at an extremely great distance, it is very difficult for telescopes to resolve them separately.
Nevertheless, astronomers have continued to discover quasar pairs one after another. Sometimes, the timing and distance of these pairs can even make researchers uneasy, because they may challenge existing theories of black hole growth.
The problem lies in the period less than 1 billion years after the birth of the universe. According to current models, black holes need at least 1 billion years to grow to millions or even billions of times the mass of the Sun by continuously accreting matter and merging with one another.
However, since Webb began operations in 2022, it has repeatedly discovered quasars powered by supermassive black holes, some of which appeared only about 400 million years after the Big Bang.
If these discoveries have already challenged existing theories, then the appearance of Nāpōwawāʻenakaulua may further shake current models. This is the third quasar pair discovered by astronomers in the cosmic dawn.
The research team found this pair in data from Webb's Aether survey. The project aims to conduct a systematic census of objects in the early universe.
Using the integral field unit of the Near-Infrared Spectrograph (NIRSpec) aboard the Webb telescope, researchers have already discovered about 200 quasars, slightly less than half of the total number of currently known quasars in the early universe.
While browsing data from the Aether project, researchers found that the quasar designated J1602+4228A was not isolated; it has a companion, designated J1602+4228B.
From ground-based telescope observations, it is almost impossible to resolve these two quasars separately. However, the Gemini North telescope eventually succeeded in this task. The key was that the observation timing was just right, and the weather conditions over Maunakea in Hawaii were also ideal. This dormant volcano is where the telescope is located.
Although the formation mechanism of Nāpōwawāʻenakaulua remains a mystery, it may help scientists gain a deeper understanding of how galaxies gradually gathered and merged during the cosmic dawn, and how early universe structures formed. This is a key stage in the evolution of the universe.
Onorato said: “Nāpōwawāʻenakaulua is a very unique environment. It provides astronomers with a natural laboratory where we can study how the first massive galaxies and their central black holes gradually assembled through direct interactions between galaxies in the early universe.”
The research team published the relevant results in The Astrophysical Journal Letters on November 10.
- https://iopscience.iop.org/article/10.3847/2041-8213/aeb11f
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