Quasars are among of the oldest and brightest remnants of the early cosmos that astronomers can currently detect, twinkling like cosmic lighthouses on a coastline 13 billion light-years from Earth.
Quasars, which stands for “quasi-stellar radio sources,” are enormous black holes that are millions to billions of times more massive than the sun and light as brilliantly as galaxies. There are quasars at the nuclei of several massive galaxies today. However, because of their extreme brightness, quasars have been observed over much of space-time, and 200 of them have been determined to have formed during the first billion years of the creation of our universe.
How, at an era when galaxies were few and huge stars were extremely uncommon, did such enormous objects emerge so early? Since the discovery of the first quasars, the subject has perplexed scientists for more than 20 years. A recent study, which was published on July 6 in the journal Nature(opens in new tab), may finally offer the long-needed solution.
Researchers simulated star formation in the early cosmos using computers, concentrating on one of the few intersections where two streams of cold, turbulent gas interacted. The natural “clouds” or reservoirs where two streams met were incredibly rare within the first billion years after the Big Bang, making them appealing but elusive topics of research. Today, streams of star-forming gas traverse the cosmos like cosmic interstates.
In the simulation, over the period of millions of years, two huge “clumps” of star-forming gas accumulated in the core of these streams. The team was surprised to find that, contrary to earlier predictions made by models of the early cosmos, these aggregates never formed into stars of typical size.
According to study co-author Daniel Whalen, a senior lecturer in cosmology at the University of Portsmouth in England, “the cold streams drove turbulence in the [gas] cloud that prevented normal stars from forming until the cloud became so massive it collapsed catastrophically under its own weight, forming two enormous primordial stars” (opens in new tab). “Two [stars] were 40,000 and 30,000 solar masses, respectively.”
According to earlier research, a quasar must have been between 10,000 and 100,000 solar masses when it was born. If so, the two enormous primordial stars from the new simulation may serve as potential “seeds” for the earliest quasars in the cosmos, according to the study’s authors.
In fact, it’s conceivable that these huge stars may have quickly collapsed into black holes and continued to ingest gas until they developed into supermassive quasars similar to those seen in the early universe. According to the experts, as the enormous black holes continue to expand, they may potentially combine, sending a flood of gravitational waves over space and time. In the future decades, it’s even conceivable that scientists may be able to see these waves using specialized telescopes, perhaps correlating the simulation’s findings.
If this finding is accurate, it will challenge decades of understanding about how stars develop in the early cosmos. According to earlier research, massive primordial stars could only originate in harsh conditions where external factors like intense UV radiation might inhibit the formation of smaller stars. However, this new simulation demonstrates that such unique conditions might not be required. Where rare streams of frigid gas converge, quasar seeds may spontaneously form.