Clemson scientists discover 5 early universe gamma-ray blazars

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In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light. For active galaxies classified as blazars, one of these jets beams almost directly toward Earth. Photo by NASA.

A team of scientists from Clemson University and NASA have discovered five of the most extreme gamma-ray blazars yet known, a discovery that may unlock the mysteries of deep space.

A blazer is a type of galaxy with an intensely bright core that’s powered by a supermassive black hole containing millions or even billions of times more material than our Sun. As matter falls into the black hole, it emits powerful jets of gamma radiation that move close to the speed of light. When the jets are aimed toward Earth, it appears particularly bright to telescopes and other instruments, allowing researchers to study some of the oldest galaxies in the universe.

The newly discovered blazars are some of the oldest and largest ever observed by scientists, according to Clemson University astrophysicist Marco Ajello. The light from these blazars has been traveling to Earth for 12.43 billion light-years, meaning astronomers are seeing the distant galaxy as it was when the universe was just 1.4 billion years old.

The team, led by Ajello, used NASA’s Fermi Gamma-Ray Space Telescope to detect the blazars. While their gamma-ray emissions can’t be seen by the naked eye, the telescope can spot them and translate them into data.

Using Fermi data, Ajello’s team began with a catalog of 1.4 million quasars, a galaxy class closely related to blazars. Over the course of a year, they narrowed their search to 1,100 objects. Of these, five were finally determined to be gamma-ray blazars.

But as with many discoveries, the findings present more questions than answers.

Ajello, for instance, is still looking to demystify how the black holes at the center of these blazars could have grown so monstrous in such a relatively short stretch of time. 

Two of blazars, for instance, contain supermassive black holes that weigh at least 1 billion solar masses, with a single solar mass equivalent to the size of the sun. The supermassive black hole at the center of our galaxy, in contrast, has a mass of 4 to 5 million times the sun’s.

“Despite their youth, these far-flung blazars host some of the most massive black holes known,” said Roopesh Ojha, an astronomer at NASA’s Goddard Space Flight Center in Maryland. “That they developed so early in cosmic history challenges current ideas of how supermassive black holes form and grow, and we want to find more of these objects to help us better understand the process.”

While galaxies and their black holes are believed to have grown over billions of years through galactic mergers, how these mergers could have created supermassive black holes of this magnitude before the universe reached its billionth birthday is an enigma that needs further analysis.

“Is it because one black hole ate a lot all the time for a very long time? Or maybe because it bumped into other black holes and merged into one? To be honest, we have no observations supporting either argument,” Ajello said.

“There are mechanisms at work that we have yet to unravel. Puzzles that we have yet to solve,” he continued. “When we do eventually solve them, we will learn amazing things about how the universe was born, how it grew into what it has become, and what the distant future might hold as the universe continues to progress toward old age.”

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