Webb Finds Oldest Quasar Pair, Black Holes 18,100 Light-Years Apart
Astronomers found the earliest known pair of quasars, seen 900 million years after the Big Bang, using Webb and Gemini North. Models cannot yet explain them.
Astronomers have found the oldest pair of quasars ever seen, two supermassive black holes only 18,100 light-years apart, observed as they were 900 million years after the Big Bang. The pair, named J1602+4228AB, was spotted in data from the James Webb Space Telescope (JWST) and confirmed with the Gemini North telescope in Hawaii, according to a report by Space.com. The results were published Nov. 10 in The Astrophysical Journal Letters.
The black holes have masses of 1.5 billion and 400 million times that of the sun. According to the research team, no definitive theory explains how even one quasar this large exists so early in the universe, let alone two.
How the pair was found
A quasar is a supermassive black hole surrounded by a flattened disk of swirling gas and dust. Friction in the disk heats the material until it glows, often brighter than all the stars in the surrounding galaxy.
The pair turned up in the Aether survey, a JWST project that is taking a census of objects in the early universe. Using the telescope’s NIRSpec integral field unit (a spectrograph that records light across a patch of sky), the survey has found 200 quasars, just under half of all the early-universe quasars currently known. While browsing that dataset, the team saw that the quasar J1602+4228A has a companion, now named J1602+4228B.
Telling the two apart is hard. At that distance and with so little space between them, ground-based telescopes struggle to resolve the two objects separately. Gemini North, on Maunakea on the island of Hawai’i, managed it thanks to perfect timing and ideal weather, according to Space.com. The object has also been given the Hawaiian name Nāpōwawāʻenakaulua.
Why the pair is a puzzle
The pair is seen during Cosmic Dawn, the period shortly after the first stars, galaxies and black holes formed. Research team leader Silvia Onorato of NOIRLab said in a statement that the universe was only a thirteenth of its present age when this light left, and that the black holes are already as massive as those seen today.
Current models say black holes need at least 1 billion years to feed and merge enough to reach masses of millions or billions of suns. JWST, which began operating in 2022, has repeatedly found quasar-powered black holes as early as 400 million years after the Big Bang. This one is the third quasar pair seen at Cosmic Dawn, and the most compact of the three. The 18,100 light-years between the black holes is roughly one-fifth the diameter of the Milky Way.
Pairs of quasars should in principle be common, because galaxy mergers are frequent and bring black holes together. Space.com lists three reasons they are hard to find: the quasar phase is short in cosmic terms, the pairs are faint and distant, and the two members are difficult to resolve individually.
What is still unclear
Space.com reports that no theory explains these black holes and says the pair could break current models. The report does not say how the two black holes will evolve or whether other early pairs will turn up in the Aether data. The sources also give no view from scientists outside the discovery team.
Why it matters
Pairs like this show black holes at an early stage of a galaxy merger. Onorato described the system as a laboratory for studying how the first massive galaxies and their central black holes came together through direct galaxy interactions in those early times. For background on the telescope that made the find possible, see our JWST explainer, and for how black holes form, see what a black hole is.
Source: Space.com
