Monday, 11 December, 2017

Massive black hole reveals when the first stars blinked on

Image Robin Dienel courtesy of the Carnegie Institution for Science Image Robin Dienel courtesy of the Carnegie Institution for Science
Theresa Hayes | 07 December, 2017, 07:41

A team led by the Carnegie Observatories' Eduardo Banados reported in the journal Nature on Wednesday that the black hole lies in a quasar dating to 690 million years of the Big Bang.

But experts believe that this and other black holes could point to a new theory - of the world being created by the Big Bounce.

Around the time of this newest quasar, the universe was emerging from a so-called Dark Ages.

The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. The quasar's light traveled some 13 billion light-years before reaching the Magellan Telescopes. For instance, at nearly a billion solar masses, the quasar's central black hole is comparatively massive.

"The new quasar is itself one of the first galaxies, and yet it already harbors a behemoth black hole as massive as others in the present-day Universe", said Xiaohui Fan, one of the authors from the University of Arizona.

The newly discovered quasar hails from the time of reionization, when light from the earliest stars and galaxies exited neutral hydrogen gas atoms, causing them to ionize, or lose an electron. "This is the most accurate measurement of that time, and a real indication of when the first stars turned on". Based on the quasar's redshift, the researchers calculated the mass of the black hole at its center and determined that it is around 800 million times the mass of the sun.

The scientists spotted the supermassive black hole within a quasar, the bright center of a galaxy that consists of both one of these enormous black holes as well as a disk of material that orbits the black hole.

The BaƱados quasar is also interesting, because it is from the time known as the epoch of reionization, when the universe emerged from its dark ages. When you think of a black hole, you're likely thinking of a stellar black hole, which forms when a star explodes in a spectacular supernova, and the remaining core collapses under the weight of its own gravity. The newly discovered quasar shines as brightly as 40 trillion suns. As more stars turned on throughout the universe, their photons reacted with neutral hydrogen, ionizing the gas and setting off what's known as the epoch of re-ionization. For one, they can be used to "X-ray" the universe over large distances.

"This adds to our understanding of our universe at large because we've identified that moment of time when the universe is in the middle of this very rapid transition from neutral to ionized", Simcoe says. As more stars formed from the remains of first-generation stars, they became "polluted" with heavier elements and in turn produce even heavier elements when they explode in supernovae. It's thought that black holes grow by accreting, or absorbing mass from the surrounding environment. But this newly-discovered black hole is more than 200 million lightyears further away - and hence, 200 million years older.

"If you start with a seed like a big star, and let it grow at the maximum possible rate, and start at the moment of the Big Bang, you could never make something with 800 million solar masses - it's unrealistic", Professor Simcoe said. "So there must be another way that it formed".