A team of astronomers say they’ve measured small-scale ripples in the cosmic web — a first.
The cosmic web is an expansive structure connecting the most sparsely populated pockets of the distant universe. It’s formed by filaments of primeval hydrogen gas, leftover material from the Big Bang.
The closest portions of the cosmic web lie roughly 11 billion light-years from the Milky Way, but researchers were able to detect structural fluctuations on scales 100,000 times smaller.
The ancient gas particles forming the cosmic web’s filaments don’t emit any light of their own. To detect them, scientists must measure the amount of light that is absorbed by the web as it travels across the vast, empty regions of the distant universe.
Recently, scientists were able to measure the lost light of a pair of quasars. Quasars are the ultraluminous events produced when a supermassive black hole at the center of a galaxy consumers large amounts of galactic material.
The radiation produced by the feeding frenzy acts like a light house. The beam’s peculiarities can offer clues as to the nature of the space in between Earth and the quasar. But quasars are rare and usually located several million light-years apart.
“Pairs of quasars are like needles in a haystack,” UC Santa Barbara physicist Joseph Hennawi said in a news release. “In order to find them, we combed through images of billions of celestial objects millions of times fainter than what the naked eye can see.”
The search was aided by a machine-learning algorithm designed to identify quasars among massive amounts of astronomical data.
Researchers found a pair of nearby quasars and studied them using the world’s most powerful telescopes.
“One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measured in this new kind of data,” said Alberto Rorai, formerly a PhD student at UCSB, and now a postdoctoral researcher at Cambridge University.
To tease out the differences between the two quasar’s manipulated light, the astronomers used supercomputers to build and run a model simulating a theoretical cosmic web. They compared their results to those of the model.
“The input to our simulations are the laws of physics and the output is an artificial universe, which can be directly compared to astronomical data,” said Jose Oñorbe, a postdoctoral researcher at the Max Planck Institute for Astronomy in Germany. “I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form.”
The team of researchers described their success in the journal Science