Evrim Yazgin
Cosmos science journalist
Astronomers have created a new map of the universe which includes 1.3 million supermassive black holes (SMBHs) at the centre of galaxies.
SMBHs have a mass between 100,000 and 10 billion times that of our own Sun. They are typically found at the centre of galaxies.
The gravitational pull of these SMBHs creates a hot, swirling mass of gas and dust which produces objects which are among the brightest in the universe. These objects are called quasars – the smoking gun that shows a supermassive black hole is there. Quasars are so bright, they can be hundreds of times more luminous than entire galaxies.
It’s these quasars that the astronomers mapped. Their results are published in the Astrophysical Journal.
“This quasar catalogue is different from all previous catalogues in that it gives us a three-dimensional map of the largest-ever volume of the universe,” says map co-creator Professor David Hogg from New York University. “It isn’t the catalogue with the most quasars, and it isn’t the catalogue with the best-quality measurements of quasars, but it is the catalogue with the largest total volume of the universe mapped.”
The furthest quasar mapped in the project was shining when the universe was “only” about 1.5 billion years old – a little over a tenth of its current age.
The map was produced using data from the European Space Agency’s Gaia space telescope. While Gaia’s focus is mapping the stars in our own galaxy, it inadvertently snaps pictures of objects much further away.
“This quasar catalogue is a great example of how productive astronomical projects are,” says Hogg. “Gaia was designed to measure stars in our own galaxy, but it also found millions of quasars at the same time, which give us a map of the entire universe.”
It’s hoped that the new map will help cosmologists understand the evolution of the universe.
Astronomers have already compared the quasar catalogue to the map of the oldest light in the universe, the cosmic microwave background (CMB).
The CMB dates to when the universe was only 380,000 years old. As the light travels through time and space to us, it is bends around regions of strong gravity including halos of dark matter which are theorised to exist around galaxies. Comparing the new map with the CMB, cosmologists can see how strongly matter clumps together over time.
“It has been very exciting to see this catalogue spurring so much new science,” says lead author Kate Storey-Fisher, a postdoctoral researcher at the Donostia International Physics Center in Spain. “Researchers around the world are using the quasar map to measure everything from the initial density fluctuations that seeded the cosmic web to the distribution of cosmic voids to the motion of our solar system through the universe.”
