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Where could the most extreme flashes of light in the universe have emerged from?
Transients are brief, extremely bright explosions thought to come from dead and dying stars.
There are phenomena out there bright enough to out-flash an entire galaxy — and they could also be the reason behind the gold jewelry you’re wearing.
Transients are brief explosions in the universe that take brightness to the ultimate extreme. It is thought that most of them can only come out of the death throes of gargantuan stars, black holes eating stars, or neutron stars (which are already zombies) smashing into each other. Transients could give us more insight into star deaths and undead stars, and stellar corpses could help us understand more about where Earth’s elements, such as gold, came from.
Some transients defy expectations. When NASA’s Chandra X-ray telescope caught the transient that later came to be known as CDF-S XT1, in just a few thousandths of a second, it unleashed as much energy as the sun could over a billion years. It did not align well with any prediction until astrophysicist Nikhil Sarin and a team of researchers from Monash University in Australia, whose recent study can be found on the preprint server arXiv, found that this transient can relate to known predictions.
“There are usually several tell-tale signs of transients that are produced by outflows traveling close to the speed of light,” Sarin told SYFY WIRE. “These include the shape of the light curve — the overall power as a function of time — and the distribution of energies of the photons emitted by the transient.”
What CDF-S XT1 matched up with was the radiation predicted from a jet, which could have only been produced in extreme conditions such as a neutron star merger (which was the most likely source for this transient), racing through the sky at nearly the light speed.
When an outflow blasts off at the speed of light like the Enterprise or the MIllennium Falcon, the power released gradually decreases. The way its photon energies should look and the shape of its light curve revealed CDF-S XT1 as something that can be predicted, since these, are already factors that predict such powerful outflows. Also, try and (hypothetically) duplicate its almost unfathomable energy by using something else besides a jet moving at warp speed. It’s nearly impossible.
Sarin and his team determined that CDF-S XT1 was probably being spewed out by a neutron star merger because of its source in the galaxy CANDELS 28573, 30 billion light years away. The properties of this galaxy were a match for those of other galaxies where neutron star merger outflows similar to CDF-S XT1 occurred. Not only that, but the transient’s properties were also most consistent with outflows coming from neutron stars. This is where your jewelry comes in. More gold, silver, uranium and plutonium are thought to be created by neutron star mergers than any other phenomenon.
“All the elements on Earth came from either explosions massive stars or some other exotic explosion,” said Sarin. “They are challenging to create in other ways. CDF-S XT1 is potentially one of the earliest binary neutron star mergers discovered, which could provide some evidence for these explosions being the most dominant source of heavy elements. “
Even with the literally brilliant observations of CDF-S XT1, the mechanism that sets off radiation at such high energy levels remains unknown. Sarin thinks it is possible that an outflow so intense causes a series of shocks, which produce high-energy gamma rays once it is far enough from its source, but there are still the questions of how far and how these shocks happen to begin with. Whether gamma rays are even produced depends on speed, thought to be 99.9 percent the speed of light. Gamma radiation would be undetectable at speeds slower than that.
“Understanding this threshold and the distribution of the speeds of the outflows launched in various explosions will help us pin down the mechanism that generates high-energy gamma-ray radiation,” he said.
Seems that even the brightest flashes in the universe are still keeping some things in the dark for now.