Massive black hole reveals when the first stars blinked on
Дек 07 2017 by Michele Stevens
The monster black hole looks to be about 800 million times as massive as our sun, and astronomers can't understand how such a behemoth could have already formed just 690 million years after the Big Bang, when the universe was just 5 percent of its current age. Astronomers have only ever discovered one object of comparable size in this era of the early universe.
"This actually suggests we've measured, to within one or two percent accuracy, the moment at which starlight first illuminated the universe", says Dr. Robert Simcoe, a physics professor at MIT and one of the authors of the study. It also did this extremely fast, at least by the standards of the universe, which scientists have estimated is 13.8 billion years old.
The black hole is even more puzzling because of what was happening in the universe at that time.
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 shift from neutral to ionized hydrogen represented a fundamental change in the universe that has persisted to this day. "This is the most accurate measurement of that time, and a real indication of when the first stars turned on".
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. This is very unlike the black holes that form in the present-day universe, which rarely exceed a few dozen solar masses. Bañados was looking in particular for quasars - some of the brightest objects in the universe, that consist of a supermassive black hole surrounded by swirling, accreting disks of matter. FIRE is a spectrometer that classifies objects based on their infrared spectra. The quasar's light traveled some 13 billion light-years before reaching the Magellan Telescopes.
The phenomenon is so big, that it is now 800 million times the mass of the sun. But this newly-discovered black hole is more than 200 million lightyears further away - and hence, 200 million years older.
The newly identified quasar appears to inhabit a pivotal moment in the universe's history.
The Big Bang started the universe as a hot, murky soup of extremely energetic particles that was rapidly expanding. The universe during this period was dark, but as stars and galaxies formed, the hydrogen ionized. Black holes grow when cosmic matter falls into them. The ionization of the cosmos' gas allowed light to move more freely through space.
The Bañados quasar is especially interesting, because it is from the time known as the epoch of reionization, when the universe emerged from its dark ages. For one, they can be used to "X-ray" the universe over large distances. That helped scientists estimate that the stars turned on roughly when it began its journey - about 696 million years after the big bang. This means that the early universe likely was conducive to the quick formation of supermassive black holes; our current universe isn't, and black holes are generally much smaller. "So there must be another way that it formed. And how exactly that happens, nobody knows".
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