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Four Quasars in One Nebula: Scientists Find an Incredible Astronomical First

Why it’s so astronomically unlikely to find a cluster of four quasars.
May 15, 2015, 5:05pm
Concept art of a quasar. Credit: ESO/M. Kornmesser

The universe is known for serving up exotic and spectacular phenomena, but even with that in mind, quasars seem too bizarre to be real. These distant objects are powered by supermassive black holes from the very early universe, and they emit massive amounts of light. In fact, one quasar can be 100 times brighter than the entire Milky Way galaxy.

Now, a team led by cosmologist Joseph Hennawi has discovered four of these objects—a quasar quartet—huddled together in a nebula 10 billion light years away. This is the first time such a large gaggle of quasars has ever been imaged, and according to Hennawi team, the odds of finding such an event are 10 million to one.

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Why such low odds? Because while quasars are ultra-luminous, they are also very rare. Quasars can be viewed as an infant life stage for young galaxies, which is why astronomers usually find them in the early universe. They are formed when gas, dust, and other matter begins to accrete around a supermassive black hole, falling inwards and reacting violently with the hole's disk.

This collision of matter is what ignites the blinding fireworks associated with quasars, but the voluminous outpouring of radiation doesn't last long. Indeed, the quasar phase typically represents only about a thousandth of a galaxy's life span.

"All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole," Hennawi and his colleagues wrote in a new paper about the quadruple quasar, published today in Science. "But because these episodes are brief, quasars are rare objects typically separated by cosmological distances."

The group that Hennawi's team found, in contrast, were all located within 600,000 light years of each other. That is an astounding distance on a human scale, but as you can see in this image of the quasar cluster, it is extremely close-knit from a cosmic perspective.

The team suspects that this never-before-seen anomaly is related to the quartet's environment more generally. Essentially, that particular slice of the sky seems to be clogged up with a lot more matter than surrounding regions, and is likely the birthplace of a massive galactic cluster.

"There are several hundred times more galaxies in this region than you would expect to see at these distances," said study co-author J. Xavier Prochaska in a Keck Observatory statement.

In other words, the larger question concerns the origins of that entire chunk of the universe, and how it became so atypically cluttered with space junk. The answer to that question will require a lot more research, and according to Hennawi, it will likely topple many current assumptions about the formation of large galactic clusters.

"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," Hennawi said in a statement. "Extremely rare events have the power to overturn long-standing theories."

Point being: You haven't heard the last of this crazy quasar quartet from the edge of space and time. Not by a cosmic long shot.