Today, stars fill the night sky. But when the universe was in its infancy, it contained no stars at all. And an international team of scientists is closer than ever to detecting, measuring and studying a signal from this era that has been traveling through the cosmos ever since that starless era ended some 13 billion years ago.
That team—led by researchers at the University of Washington, the University of Melbourne, Curtin University and Brown University—reported last year in the Astrophysical Journal that it had achieved an almost 10-fold improvement of radio emission data collected by the Murchison Widefield Array. Team members are currently scouring the data from this radio telescope in remote Western Australia for a telltale signal from this poorly understood “dark age” of our universe.
“We think the properties of the universe during this era had a major effect on the formation of the first stars and set in motion the structural features of the universe today,” said team member Miguel Morales, a UW professor of physics. “The way matter was distributed in the universe during that era likely shaped how galaxies and galactic clusters are distributed today.”
The 13 billion-year-old signal that Morales and his team are after is electromagnetic radio emission that the neutral hydrogen emanated at a wavelength of 21 centimeters. The universe has expanded since that time, stretching the signal out to nearly 2 meters.
That signal should harbor information about the dark age and the events that ended it, Morales said.
The Murchison Array is the team’s primary tool. This radio telescope consists of 4,096 dipole antennas, which can pick up low-frequency signals like the electromagnetic signature of neutral hydrogen.
But those sorts of low-frequency signals are difficult to detect due to electromagnetic “noise” from other sources bouncing around the cosmos, including galaxies, stars and human activity. Morales and his colleagues have developed increasingly sophisticated methods to filter out this noise and bring them closer to that signal. In 2019, the researchers announced that they had filtered out electromagnetic interference—including from our own radio broadcasts—from more than 21 hours of Murchison Array data.
Source: “Scientists close in on 12-billion-year-old signal from the end of the universe’s ‘dark age’” PhysOrg, 12 June 2020. <https://phys.org/news/2020-06-scientists-billion-year-old-universe-dark-age.html>