Astronomers have discovered what may be the brightest object in the universe, a quasar with a black hole at its heart growing so fast that it swallows the equivalent of a sun a day.
Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have characterised a bright quasar, finding it to be not only the brightest of its kind, but also the most luminous object ever observed. Quasars are the bright cores of distant galaxies and they are powered by supermassive black holes. The black hole in this record-breaking quasar is growing in mass by the equivalent of one Sun per day, making it the fastest-growing black hole to date.
The record-breaking quasar shines 500 trillion times brighter than our sun. The black hole powering this distant quasar is more than 17 billion times more immense than our sun, an Australian-led team reported Monday in the journal Nature Astronomy.
While the quasar resembles a mere dot in images, scientists envision a ferocious place.
The black holes powering quasars collect matter from their surroundings in a process so energetic that it emits vast amounts of light. So much so that quasars are some of the brightest objects in our sky, meaning even distant ones are visible from Earth. As a general rule, the most luminous quasars indicate the fastest-growing supermassive black holes.
The rotating disk around the quasar’s black hole — the luminous swirling gas and other matter from gobbled-up stars — is like a cosmic hurricane.
“We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion Suns, and eats just over a Sun per day. This makes it the most luminous object in the known Universe,” says Christian Wolf, an astronomer at the Australian National University (ANU) and lead author of the study published today in Nature Astronomy. The quasar, called J0529-4351, is so far away from Earth that its light took over 12 billion years to reach us. This quasar is the most violent place that we know in the universe.”
The European Southern Observatory spotted the object, J0529-4351, during a 1980 sky survey, but it was thought to be a star. It was not identified as a quasar — the extremely active and luminous core of a galaxy — until last year. Observations by telescopes in Australia and Chile’s Atacama Desert clinched it.
“The exciting thing about this quasar is that it was hiding in plain sight and was misclassified as a star previously,” Yale University’s Priyamvada Natarajan, who was not involved in the study, said in an email.
These later observations and computer modelling have determined that the quasar is gobbling up the equivalent of 370 suns a year — roughly one a day. Further analysis shows the mass of the black hole to be 17 to 19 billion times that of our sun, according to the team. More observations are needed to understand its growth rate.
The quasar is 12 billion light-years away and has been around since the early days of the universe. A light-year is 5.8 trillion miles.
“All this light comes from a hot accretion disc that measures seven light-years in diameter — this must be the largest accretion disc in the Universe,” says ANU PhD student and co-author Samuel Lai. Seven light-years is about 15 000 times the distance from the Sun to the orbit of Neptune.
And, remarkably, this record-breaking quasar was hiding in plain sight. “It is a surprise that it has remained unknown until today, when we already know about a million less impressive quasars. It has literally been staring us in the face until now,” says co-author Christopher Onken, an astronomer at ANU. He added that this object showed up in images from the ESO Schmidt Southern Sky Survey dating back to 1980, but it was not recognised as a quasar until decades later.
Finding quasars requires precise observational data from large areas of the sky. The resulting datasets are so large, researchers often use machine-learning models to analyse them and tell quasars apart from other celestial objects. However, these models are trained on existing data, which limits the potential candidates to objects similar to those already known. If a new quasar is more luminous than any other previously observed, the programme might reject it and classify it instead as a star not too distant from Earth.
The fastest-growing black hole ever observed will also be a perfect target for the GRAVITY+ upgrade on ESO’s VLT Interferometer (VLTI), which is designed to accurately measure the mass of black holes, including those far away from Earth. Additionally, ESO’s Extremely Large Telescope (ELT), a 39-metre telescope under construction in the Chilean Atacama Desert, will make identifying and characterising such elusive objects even more feasible.
Finding and studying distant supermassive black holes could shed light on some of the mysteries of the early Universe, including how they and their host galaxies formed and evolved. But that’s not the only reason why Wolf searches for them. “Personally, I simply like the chase,” he says. “For a few minutes a day, I get to feel like a child again, playing treasure hunt, and now I bring everything to the table that I have learned since.” (ESO/AP)