Peering deep into the infancy of the universe, the European Southern Observatory’s Very Large Telescope (VLT) recently confirmed the discovery of the brightest and fastest growing quasar. Quasars are luminous objects in the night sky, powered by gas falling into a large black hole at the center of a galaxy.
The discovery of this record-breaking object was fascinating enough. But another crucial aspect of the announcement is that it raises big questions about the formation of galaxies in the early universe.
It remains a mystery how this quasar, which existed less than two billion years after the Big Bang, could grow so large so quickly. Investigating this mystery could even lead to a rethink of how galaxies formed.
Black holes, the densest objects in the universe, get this name because their gravity is so incredibly strong that not even light can escape their grasp. How then can a black hole be the origin of such an intense light source?
Well, in some galaxies, where the black hole is sufficiently large, matter is sucked in at a ferociously fast rate. As it spirals inward, violent collisions between gases, dust and stars result in the emission of enormous amounts of light energy. The larger the black hole, the more violent the collisions and the more light is emitted.
The quasar that was the subject of the latest study, known as J0529-4351, has a mass equivalent to 17 billion suns and is incredibly large.
There is a spiral disk of matter seven light-years wide at the center of the Milky Way, and the black hole is growing by accumulating (accumulating) this matter. The width of the disk is comparable to the distance between Earth and the nearest galaxy, Alpha Centauri.
Hide in plain sight
The black hole is growing rapidly and consuming a record amount of mass, equivalent to one sun per day. This intense accretion of matter releases an amount of radiant energy equivalent to one quadrillion (one thousand trillion) suns.
This raises the question of why such a bright object has only just been identified in the night sky, despite decades of astronomical observations. It turns out that this sneaky quasar had been hiding in plain sight.
Despite its astonishing brightness, J0529-4351 is very far away, meaning it blends in seamlessly with a sea of fainter stars much closer to Earth. In fact, this quasar is so far away that the light it emits takes a whopping 12 billion years to reach us here on Earth.
The age of the universe is approximately 13.7 billion years. This quasar existed only 1.7 billion years after the Big Bang, at the beginning of the universe.
The expansion of the universe after the Big Bang allows us to measure the distance to, and therefore the age of, this quasar. A long-known simple formula called Hubble’s law states that knowing the speed at which an object is moving away from us allows us to calculate how far away it is.
The collisions that occur when matter enters this quasar’s black hole raise it to scorching temperatures of 10,000 °C. Under these conditions, the atoms in the system emit a characteristic spectrum of light.
These discrete frequencies of light form a kind of barcode that astronomers can use to identify the elemental compositions of objects in the night sky.
When an object emitting light moves away from us, the frequency of that perceived light shifts, just as the sound frequency of an ambulance siren shifts depending on whether it is moving toward or away from you.
This shift observed in astronomical objects is known as redshift. This, together with Hubble’s law, has allowed both the age and distance (both properties are linked in cosmology) of J0529-4351 to be confirmed.
This bright beacon from the early universe has raised an important question that baffles astronomers: How did this black hole grow so quickly into such a massive object in such a relatively short time? According to generally accepted models of the early universe, it should have taken longer to grow to this size.
Moreover, even more could be found in the coming years by fine-tuning the artificial intelligence (AI) models used to scan telescope data for these unusual objects. If they look like J0529-4351, physicists should seriously reconsider their models of the early universe and galaxy formation.
The fastest-growing black hole ever observed will be the perfect target for a system called Gravity+, an upcoming upgrade of an instrument on the Very Large Telescope called an interferometer. This interferometer is an ingenious way to combine data from the four separate telescopes that make up the VLT.
Gravity+ is designed to accurately measure the rotation speed and mass of black holes directly, especially if they are far from Earth.
In addition, the European Southern Observatory’s Extremely Large Telescope, a 39-meter diameter reflecting telescope, is currently under construction in Chile’s Atacama Desert. This is designed to detect the optical and near-infrared wavelengths characteristic of distant quasars and will make identifying and characterizing such elusive objects even more likely in the future.
Robin Smith, Senior Lecturer in Physics, Sheffield Hallam University
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