"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," said astrophysicist Marco Ajello, who has
spent much of his career studying the evolution of distant galaxies.
"Our next step is to
increase our understanding of the mechanisms involved in the formation,
development and activities of these amazing objects, which are the most
powerful accelerators in the universe. We can't even come close to replicating
such massive outputs of energy in our laboratories. The complexities we're
attempting to unravel seem almost as mysterious as the black holes
themselves."
When the universe was
young, a supermassive black hole -- bloated to the bursting point with stupendous
power -- heaved out a jet of particle-infused energy that raced through the
vastness of space at nearly the speed of light. Billions of years later
scientists identified this black hole and four others similar to it that range
in age from 1.4 billion to 1.9 billion years old. These objects emit copious
gamma rays, light of the highest energy, that are billions of times more
energetic than light that is visible to the human eye.
The previously known
earliest gamma-ray blazars -- a type of galaxy whose intense emission is
powered by extremely powerful relativistic jets launched by monstrous black
holes -- were more than 2 billion years old. Currently, the universe is
estimated to be approximately 14 billion years old.
Ajello conducted his
research in conjunction with Clemson post-doc Vaidehi Paliya and Ph.D candidate
Lea Marcotulli. The trio worked closely with the Fermi-Large Area Telescope
collaboration, which is an international team of scientists that includes
Roopesh Ojha, an astronomer at NASA's Goddard Space Flight Center in Greenbelt,
Maryland; and Dario Gasparrini of the Italian Space Agency. Their scientific
paper titled "Gamma-Ray Blazars Within the First 2 Billion Years" was
published Monday in a journal called Astrophysical Journal Letters. (Ackermann,
M., et al. 2017, ApJL, 837, L5.)
The Clemson team's
breakthroughs were made possible by recently juiced-up software on NASA's Fermi
Gamma-ray Telescope. The refurbished software significantly boosted the
orbiting telescope's sensitivity to a level that made these latest discoveries
possible.
"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. 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."
Using Fermi data, Ajello
and Paliya began with a catalog of 1.4 million quasars, which are galaxies that
harbor at their centers active supermassive black holes. Over the course of a
year, they narrowed their search to 1,100 objects. Of these, five were finally
determined to be newly discovered gamma-ray blazars that were the farthest away
- and youngest - ever identified.
"After using our
filters and other devices, we were left with about 1,100 sources. And then we
did the diagnostics for all of these and were able to narrow them down to 25 to
30 sources," Paliya said. "But we still had to confirm that what we
had detected was scientifically authentic. So we performed a number of other
simulations and were able to derive properties such as black hole mass and jet
power. Ultimately, we confirmed that these five sources were guaranteed to be
gamma-ray blazars, with the farthest one being about 1.4 billion years old from
the beginning of time."
Marcotulli, who joined
Ajello's group as a Ph.D student in 2016, has been studying the blazars'
mechanisms by using images and data delivered from another orbiting NASA
telescope, the Nuclear Spectroscopic Telescope Array (NuSTAR). At first,
Marcotulli's role was to understand the emission mechanism of gamma-ray blazars
closer to us. Now she is turning her attention toward the most distant objects
in a quest to understand what makes them so powerful.
"We're trying to
understand the full spectrum of the energy distribution of these objects by
using physical models," Marcotulli said. "We are currently able to
model what's happening far more accurately than previously devised, and
eventually we'll be able to better understand what processes are occurring in
the jets and which particles are radiating all the energy that we see. Are they
electrons? Or protons? How are they interacting with surrounding photons? All
these parameters are not fully understood right now. But every day we are
deepening our understanding."
All galaxies have black
holes at their centers - some actively feeding on the matter surrounding them,
others lying relatively dormant. Our own galaxy has at its center a super-sized
black hole that is currently dormant. Ajello said that only one of every 10
black holes in today's universe are active. But when the universe was much
younger, it was closer to a 50-50 ratio.
The supermassive black holes at the center of the five newly discovered
blazar galaxies are among the largest types of black holes ever observed, on
the order of hundreds of thousands to billions of times the mass of our own
sun. This has stunned astronomers and got everyone’s attention.
And their accompanying
accretion disks - rotating swirls of matter that orbit the black holes - emit
more than two trillion times the energy output of our sun.
One of the most surprising
elements of Ajello's research is how quickly - by cosmic measures - these
supersized black holes must have grown in only 1.4 billion years. 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.
"How did these incomprehensibly enormous and energy-laden black
holes form so quickly?" Ajello said. "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. 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."
Via Dailygalaxy