Scientists looking for some of the first galaxies in the early universe made a surprise discovery: a more powerful than expected active galaxy spewing a jet of material near the speed of light.
These powerful radio jets traveled 13 billion light years to reach us, and they came from an ancient source — an extremely bright galactic nucleus known as a quasar. Detailed in a study published Monday in the Astrophysical Journal, the discovery marks the most distant source of radio jets to date and provides clues on how black holes that lurk at the center of ancient galaxies grew to their supermassive size.
WHAT'S NEW — Using the European Southern Observatory’s (ESO) Very Large Telescope, a team of scientists discovered a quasar that lies around 13 billion light years away from Earth.
The universe is believed to be 13.8 billion years old, meaning this may be among the first population of large galaxies at a point when the universe was just 780 million years old.
The newly discovered quasar was dubbed P172+18. While more distant quasars have been discovered previously, this is the first time that astronomers have been able to detect radio jets being emitted from a quasar this distant.
In fact, only about 10 percent of all quasars emit light at radio frequencies that can be detected and are considered to be “radio loud.”
“As soon as we got the data, we inspected it by eye, and we knew immediately that we had discovered the most distant radio-loud quasar known so far,” Eduardo Bañados, a researcher at the Max Planck Institute for Astronomy in Germany, and lead author of the new study, said in a statement.
HERE'S THE BACKGROUND — Quasars are regions of galaxies that have an abundance of gas and dust near the supermassive black hole believed to be at the center of most large galaxies. The material spirals around and form an accretion disc of superheated material that often shoots out in a jet from the black hole.
The name “quasar” is derived from them being “quasi-stellar objects,” as a single quasar emits the same amount of light as a trillion stars, all the while occupying an area of space that is smaller than our Solar System. Due to their high energy, quasars often outshine the galaxies that host them.
Scientists hunt for ancient quasars located billions of light years away to inform them of the conditions of the early universe, and how galaxies formed and evolved over time. Additionally, quasars can also help scientists better understand the relationship between galaxies and the black holes at their center.
Ancient black holes
The newly discovered quasar houses a black hole that was growing at an unusually rapid rate. The black hole is around 300 million times more massive than the Sun, and is consuming the surrounding gas at an alarming rate.
“The black hole is eating up matter very rapidly, growing in mass at one of the highest rates ever observed,” Chiara Mazzucchelli, a fellow at ESO in Chile, and lead author of the study, said in a statement.
The scientists behind the discovery believe that the black hole is growing at this speed is due to the material being emitted by the quasar. The jets may be disturbing the gas around the black hole, making it easier for the black hole to swallow up surrounding material and grow in size.
Why it matters — The discovery of the quasar and its accompanying black hole provides scientists with insight on how black holes grow to their massive size so early on in the universe, in such a short period of time following the Big Bang.
Quasars are also believed to be among the first sources of light that reionized the universe. As the early universe cooled after the Big Bang, the cosmos were opaque due to the presence of neutral hydrogen throughout the universe. Something caused the neutral hydrogen to flip into an ionized state, making the interstellar void transparent. Knowing the process by which the universe was reionized helps scientists reconstruct the earliest years of the universe.
This galaxy is especially important because it is one of the oldest large galaxies discovered in the early universe and galaxies may be what caused the reinoization of the cosmos.
What’s next — Astronomers are hoping to find more of these distant quasars in order to analyze the relationship they have with their black hole companions and figure out how these cosmic beasts form and grow throughout the universe.
“I find it very exciting to discover ‘new’ black holes for the first time, and to provide one more building block to understand the primordial universe, where we come from, and ultimately ourselves,” Mazzucchelli said.
Abstract: Radio sources at the highest redshifts can provide unique information on the first massive galaxies and black holes, the densest primordial environments, and the epoch of reionization. The number of astronomical objects identified at z > 6 has increased dramatically over the last few years, but previously only three radio-loud (R2500 = fν,5 GHz/fν,2500 Å > 10) sources had been reported at z > 6, with the most distant being a quasar at z = 6.18. Here we present the discovery and characterization of PSO J172.3556+18.7734, a radio-loud quasar at z = 6.823. This source has an Mg ii-based black hole mass of ~3 × 108M⊙ and is one of the fastest accreting quasars, consistent with super-Eddington accretion. The ionized region around the quasar is among the largest measured at these redshifts, implying an active phase longer than the average lifetime of the z 6 quasar population. From archival data, there is evidence that its 1.4 GHz emission has decreased by a factor of two over the last two decades. The quasar's radio spectrum between 1.4 and 3.0 GHz is steep (α = −1.31). Assuming the measured radio slope and extrapolating to rest-frame 5 GHz, the quasar has a radio-loudness parameter R2500 ~ 90. A second steep radio source (α = −0.83) of comparable brightness to the quasar is only 231 away (~120 kpc at z = 6.82; projection probability <2%), but shows no optical or near-infrared counterpart. Further follow-up is required to establish whether these two sources are physically associated.