Twinkling like cosmic lighthouses on a shore 13 billion light-years from Earth, quasars are some of the oldest and brightest relics of the early universe that astronomers can detect today.
Short for “quasi-stellar radio sources,” quasars are massive black holes which shine as brightly as galaxies and are millions to billions of times more massive than The Earthit’s sun Today, quasars exist at the centers of many large galaxies. But thanks to their extraordinary brightness, quasars have been traced far away space timewith approximately 200 of these identified as having formed in the first billion years of our universe’s history.
How could such massive objects form so early when galaxies are rare and large stars are extremely rare? The question has plagued researchers for more than two decades since the first quasars were identified—and now, a new study published July 6 in the journal Nature (opens in new tab)may provide a long-sought answer.
Using a computer simulation, the researchers modeled star formation in the early universe by focusing on one of the rare junctions where two streams of cold, turbulent gas met. While streams of star-forming gas criss-cross the universe like cosmic interstates today, natural “clouds” or reservoirs where two streams meet were extremely rare during the first billion years after Big bangmaking them enticing but elusive areas of research.
In the simulation, two large “lumps” of star-forming gas accumulate at the center of these streams over millions of years. But, to the team’s surprise, these clusters never coalesced into normal-sized stars, as previous models of the early universe predicted.
“The cold currents caused turbulence in the [gas] cloud that prevented normal stars from forming until the cloud became so massive that it collapsed catastrophically under its own weight, forming two giant protostars,” study co-author Daniel Whalen, senior lecturer in cosmology at the University of Portsmouth in England , said in a statement (opens in new tab). “One thing [star] was 30,000 solar masses and another was 40,000.”
Previous studies have estimated that the quasar must have measured somewhere between 10,000 and 100,000 solar masses at birth. If that’s the case, both massive protostars from the new simulation could be viable “seeds” for the first quasars in the universe, the study authors wrote.
In fact, it’s possible that both massive stars collapsed into black holes almost instantaneously and then continued to swallow gas until they grew into supermassive quasars like the ones scientists found in the early universe. As the monstrous black holes continue to grow, they may even merge, releasing a stream of space-time waves known as gravitational waves, the researchers wrote. It is possible that scientists may even detect these waves using special observatories in the coming decades, potentially confirming the results of the simulation.
If confirmed, this research would overturn decades of thought about star formation in the early universe. Previous studies have suggested that large protostars can only form in extreme environments where external forces, such as strong ultraviolet radiation, can prevent the formation of smaller stars. However, this new simulation shows that such exotic environments may not be necessary. Quasar seeds can occur naturally where rare streams of cold gas occur.
“The first supermassive black holes were simply a natural consequence of the formation of structure in [the early universe] — children of space networkWallen said.
Originally published on Live Science.