- “We think Fermi has detected just the tip of the iceberg, the first examples of a galaxy population that previously has not been detected in gamma rays."
Scientists at Clemson University have identified five of the oldest and largest gamma-ray blazars yet known, a discovery that may unlock the mysteries of deep space.
According to Clemson University astrophysicist Marco Ajello, a blazar is a type of active galactic nuclei – a supermassive black hole at the center of a galaxy with a large disk of matter whirling around it. As matter falls into the supermassive 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. That allows researchers like Ajello to study some of the oldest black holes in the universe.
The gamma rays from the newly discovered blazars traveled at the speed of light for at least 1.2 billion years before reaching Earth. Previously, the most distant blazar galaxy emitted its light when the universe was 2.1 billion years old. That means the new blazars are some of the oldest ever observed, Ajello said.
Watch below to learn more about the discovery:
Also, the supermassive black holes within the blazars are much larger than Earth’s sun.
Scientists measure the size of celestial bodies in solar masses, with a single solar mass equivalent to the size of the sun. Two of the black holes weigh at least 1 billion solar masses, meaning matter is continuously falling inward, corralled into a disk and heated before making the final plunge to the black hole. The supermassive black hole at the center of our galaxy, in contrast, has a mass of 4 to 5 million times the sun’s.
“The discovery of these supermassive black holes, which launch jets that emit more energy in one second than our sun will produce in its entire lifetime, was the culmination of a yearlong research project,” Ajello said.
Ajello conducted his research with graduate students Vaidehi Paliya and Lea Marcotulli, and an international team of scientists from the Fermi-Large Area Telescope collaboration. That includes Roopesh Ojha, an astronomer at NASA’s Goddard Space Flight Center in Maryland, and Dario Gsparrini of the Italian Space Agency.
The team of scientists used NASA’s Fermi Gamma-Ray Space Telescope to detect the five previously undiscovered gamma-ray blazars. In fact, recent accuracy improvements significantly boosted the telescope’s sensitivity, allowing it to process images from deep space.
“People are calling it the cheapest refurbishment in history,” Ajello 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.”
While gamma-ray emissions can’t be seen by the naked eye, the Fermi telescope can spot them and translate them into data. Over the course of a year, Ajello and his team sifted through a catalog of about 1.4 million quasars, which are galaxies with active supermassive black holes at their core, and identified the five undiscovered blazars.
But as with many discoveries, the findings present more questions. That includes the mystery of how the newly discovered black holes grew to be at least 1 billion solar masses in just 1.4 billion years. In terms of cosmic measures, that’s barely enough time for a black hole to reach such monstrous proportions.
“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.”
Ajello and the other scientists plan to search for more distant blazar galaxies to understand the emission mechanisms that makes them so powerful. The newly discovered galaxies’ accompanying accretion disks – rotating swirls of matter that orbit the black holes – emit more than 2 trillion times the energy output of Earth’s sun.
“We think Fermi has detected just the tip of the iceberg, the first examples of a galaxy population that previously has not been detected in gamma rays,” Ajello said.