'Sprawling' New Galaxy Cluster Found Hiding Around A Quasar

Quasars are extremely luminous and active objects, ranking as the brightest in the universe, the Inquisitr previously reported. Made up of a supermassive black hole surrounded by an accretion disk of gaseous material, quasars emit light, energy, and radiation as they feed on the gas floating all around them.

Yet one particular quasar found decades ago has drawn a lot of attention after astronomers uncovered that there was more to it than they previously thought. Dubbed PKS1353-341, the quasar is located some 2.4 billion light-years from Earth and was initially believed to signal the presence of a single distant galaxy.

However, it turned out that the quasar had quite a large company all along, as an entire cluster of hundreds of galaxies has recently been spotted around the supermassive black hole in its center, reports Science Daily.

This unexpected discovery belongs to a team of scientists led by the Massachusetts Institute of Technology (MIT) in Cambridge and is the first of its kind.

It also marks the first result of an exciting survey called Clusters Hiding in Plain Sight (CHiPS), which, as the name so eloquently suggests, aims to uncover massive galaxy clusters that were overlooked or misidentified in past X-ray observations, the team explained in a paper published on August 16 in the Astrophysical Journal.

It all started with another galaxy cluster discovery back in 2012 — the Phoenix cluster, one of the brightest and most massive in the entire universe — which revealed for the very first time that these complex objects might not always look like we think they should.

Objects detected in X-ray images of the cosmos typically look like points, in the case of quasars and highly active black holes, or like "fluffs," when X-ray telescopes spot a galaxy cluster, the team points out.

"This idea that you could have a rapidly accreting black hole at the center of a cluster — we didn't think that was something that happened in nature," said study co-author Michael McDonald, an assistant professor of physics at MIT's Kavli Institute for Astrophysics and Space Research. McDonald was also part of the team that discovered the Phoenix cluster six years ago, notes MIT.

The newfound galaxy cluster was detected after the scientists combed through archival data "looking for point sources inside fluffy things," explained study lead author Taweewat Somboonpanyakul, also from MIT. The team then analyzed their findings with a ground-based and a space telescope, namely the Magellan Telescope in Chile and NASA's Chandra X-Ray Observatory, to confirm their discovery.

The reason why astronomers only caught wind of the galaxy cluster around PKS1353-341 just now is because the quasar is so luminous that its light was obscuring the galaxy cluster, allowing it to remain hidden for several decades. It's 46 billion times brighter than the sun, the team has found.

According to the team, this spectacular intensity of the quasar's light — bright enough to conceal a galaxy cluster 690 trillion times more massive than the sun — might be only temporary. Their theory is that the quasar became so bright after munching on its accretion disk in a "temporary feeding frenzy," which made it emit a fantastic amount of radiation as light, explains MIT.

"This might be a short-lived phase that clusters go through, where the central black hole has a quick meal, gets bright, and then fades away again," said McDonald. "This could be a blip that we just happened to see. In a million years, this might look like a diffuse fuzzball."

The team is convinced that many more hidden galaxy clusters are lurking in the universe. Finding at least some of them would help astronomers estimate how much matter there is in the universe and how fast the universe is expanding, shows MIT.