Quasars are one of the rarest objects in the Universe. They form as a supermassive black hole at the center of a galaxy collects matter. This matter powers the quasar. When active, quasars can shine hundreds of times brighter than their host galaxies.
Imagine astronomers’ surprise when they discovered four quasars in close proximity to each other. The astronomers said the chances of this happening are just one in ten million.
What made this part of space so special? The sheer number of galaxies.
“There are several hundred times more galaxies in this region than you would expect to see at these distances,” said Xavier Prochaska, a professor of astronomy and astrophysics at UC Santa Cruz and the principal investigator of the Keck observations.
The quasar quartet lies in a proto-cluster of galaxies 10 billion light-years away from Earth. We are seeing a giant cluster of galaxies less than 4 billion years after the big bang. It’s also surrounded by a vast nebula of dense cool gas.
How does the team of astronomers explain their lucky find? “If you discover something which, according to current scientific wisdom, should be extremely improbable, you can come to one of two conclusions: either you just got very lucky, or you need to modify your theory,” said Joseph Hennawi, one of the authors of a study published in Science.
Let’s assume luck still plays a role. One theory lies with the proto-cluster. Astronomers speculate quasars can be triggered when galaxies collide. That would occur much more frequently in a dense cluster of galaxies.
Co-author Fabrizio Arrigoni-Battaia also points at the giant nebula of cold gas as an important part. Quasars use this gas and other matter as fuel. The amount of cold gas present would help fuel multiple quasars.
But, the vast nebula of cold gas throws a wrench in current models of how massive structures in the universe form.
“Our current models of cosmic structure formation based on supercomputer simulations predict that massive objects in the early universe should be filled with rarefied gas that is about ten million degrees, whereas this giant nebula requires gas thousands of times denser and colder,” coauthor Sebastiano Cantalupo said.
This quasar discovery could lead to revised models on quasar evolution and how massive structures form in the Universe.
The Keck I Telescope. Meet the telescope that found the quasar quartet.
Hawaii is home to the W.M. Keck Observatory. A pair of telescopes sit atop Hawaii’s Mauna Kea volcano. Besides the beautiful weather, the telescopes also enjoy few city lights. And, you can’t beat the view.
Each telescope stands eight stories tall and weighs a massive 300 tons.
Here is a fantastic video showing the insides of the Keck Telescope and the kind of observations it makes.