Scientists from Clemson University and NASA have identified five of the farthest gamma-ray blazars yet known, a discovery that could someday help unlock answers about the evolution of the universe.
A blazar is a type of galaxy whose intense emissions are powered by a supermassive black hole that has a large disk of material whirling around it, according to a press release from NASA. When material falls from the disk toward the black hole, it emits a pair of particle jets that blasts out gamma radiation near the speed of light. When the jets are aimed toward Earth, the radiation appears particularly bright to telescopes and other specialized instruments.
The gamma rays from the five newly discovered blazars were blasted out towards Earth when the universe was somewhere between 1.9 to 1.4 billion years old, or nearly 10 percent of its present age, according to Clemson University astrophysicist Marco Ajello.
Before these five blazars were detected, the most distant blazar that had been seen by scientists emitted its light when the universe was close to 2.1 billion years old. The universe is currently estimated to be approximately 14 billion years old.
Ajello and his research partners – Lea Marcotulli and Vaidehi Paliya – made the discovery with help from an international team of scientists that includes Roopesh Ojha, an astronomer at NASA’s Goddard Space Flight Center, and Dario Gasparrini of the Italian Space Agency. The team of scientists used the Fermi Gamma-Ray Space Telescope to detect the incoming gamma radiation, according to Ajello.
Launched in 2008, the telescope is capable of detecting gamma rays with more than 300 billion times the energy of visible light, according to NASA. Once the telescope detects gamma radiation, it sends information back to scientists on Earth who then use the data to create pictures of the objects Fermi studies. These pictures ultimately help scientists like Ajello discover the sources of gamma rays.
Using Fermi data, Ajello’s team began with a catalog of 1.4 million quasars, a type of galaxy 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.
The discovery of the five blazars wouldn’t have been possible without a significant processing software update to the Fermi Large Area Telescope, according to Ajello. The update, which occurred in 2015, increased the telescope’s sensitivity by about 40 percent, particularly at lower frequencies.
“People are calling it the cheapest refurbishment in history,” he said. “Normally, for the Hubble Space Telescope, NASA had to send someone up to space to physically make these kinds of improvements. But in this case, they were able to do it remotely from an Earth-bound location. And of equal importance, the improvements were retroactive, which meant that the previous six years of data were also entirely reprocessed. This helped provide us with the information we needed to complete the first step of our research and also to strive onward in the learning process.”
Now Ajello and his teammates are working to demystify how the supermassive black holes at the center of these newly discovered blazars could have grown to such monstrous proportions in such a relatively short stretch of time. In terms of our current knowledge of how black holes grow, 1.4 billion years is barely enough time for a black hole to reach the mass of the ones discovered by Ajello’s team.
Two of the blazars, for instance, boast black holes of a billion solar masses or more, 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 between 4 and 5 million times the sun’s.
“There are mechanisms at work that we have yet to unravel. Puzzles that we have yet to solve. 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,” said Ajello.