Biggest, brightest Quasar found yet
So far away, we see it as it looked 12 billion years ago
Stars shine. When we look up into the sky at night, we see them sparkling against the blackness of space. We can even see the band of the Milky Way with its more than 100 billion stars that make up our galaxy.
But down in the heart of our galaxy lurks an object that is blacker than black – a giant black hole.
It is as massive as five million stars like our Sun, yet only 30 million kilometres across.
Compared to our solar system, it could fit inside Mercury’s orbit.
This black hole formed about 13 billion years ago at the beginning of the universe when a star at the end of its life exploded as a supernova and left behind a remnant black hole about 10 times the mass of our Sun.
Down in the centre of our galaxy, stars are much closer together than they are out here, 30,000 light years away, where our Sun orbits the galaxy.
So, stars in the heart of the galaxy pass close to the black hole.
When that happens, tides caused by the extreme gravity of the black hole tear the star apart into a cloud of gas that then swirls down into the black hole, like water spinning down a plughole.
That releases stupendous amounts of energy causing the swirling cloud of gas to shine brightly. But only before it falls into the black hole.
Nothing gets out of a black hole, not even light. And a black hole is simple: the more it eats, the bigger it gets. The bigger it gets, the more stars it can eat.
So the black hole in the galaxy centre has grown for 13 billion years, until it is now five million times the mass of our Sun. We call it a “supermassive black hole”.
The spectrum of a star is a rainbow where some light is missing at various colours in what we call dark spectral lines.
These arise from the elements absorbing light at particular colours. They allow us to see what the star is made of, and using an effect called the Doppler shift, we can also measure how fast they are moving towards us and away from us.
Most stars move at speeds of tens of kilometres per second with respect to us as they too orbit about the Milky Way. But galaxies move away from us, and the farther they are the faster they go.
The furthest galaxies are the fastest ones, moving at nearly the speed of light. This is the expanding universe. By measuring a galaxy’s speed, we determine its distance.
In 1963, Prof Maartin Schmidt (1929 – 2022) of Caltech was puzzling over some spectra from objects that look like fuzzy stars.
What he found, much to his surprise and everyone else’s, is that these Quasi-Stellar Objects (now called Quasars) are moving fast, thus they are far, far away.
Yet they are small, since they look like stars, not galaxies.
They are also stupendously bright. What could they be?
Then Donald Lynden-Bell (1935 – 2018), of Cambridge University, figured out that the Quasars are powered by incredible amounts of gas swirling down into the maws of giant black holes, like the one in our galaxy.
We now know that almost all galaxies have these supermassive black holes, some of which have masses of billions of Suns.
As energy is released by the falling gas, giant jets shoot out of the galaxies at nearly the speed of light, making Quasars the brightest things in the universe.
Now, on February 19, a group of astronomers led by Prof Christian Wolf of the Australian National University announced they have found the biggest, baddest, brightest Quasar yet. It has the romantic name J0529-4351 and it is so far away that we are seeing it as it looked 12 billion years ago when the universe was young.
J0529-4351 has a mass 17 billion times that of our Sun, and it shines 500 trillion times brighter.
It is the brightest object known. To feed this profligate power output, it eats more than the mass of our Sun every day.
The disk of gas swirling about it is so large it would stretch from here to beyond Proxima and Alpha Centauri, the nearest stars.
How could a black hole this massive have already formed when the universe was still young?
Maybe our ideas about black holes forming first from supernovas, then growing as they swallow gas and stars, needs more thought.
Could black holes have formed first, then galaxies grew around them in the infancy of the universe? No-one knows.
New studies with the world’s largest telescopes of J0529-4351 and other Quasars like it may hold the answers. extraordinary professor at NorthWest University in Mahikeng. He has an A-1 rating from the South African National Research Foundation, its highest rating.
He also holds appointments in the UK of emeritus professor at the University of Central Lancashire and visiting professor of Astrophysics at the University of Lincoln.
He was previously professor of astronomy at the University of Cape Town, where he worked for 24 years. He has more than 500 professional publications and was awarded the 2022 Service Award of the Royal Astronomical Society for a lifetime of public outreach and for his service on many international committees. He and his wife, who is originally from Makhanda, now live in Port Alfred.