New map of the cosmos uses gravitational waves to expose hidden black holes and cosmic structure

An international study led by astrophysicists from Swinburne University of Technology has fashioned the most detailed maps of gravitational waves across the cosmos to date. The study has also produced the biggest ever galactic-scale gravitational wave detector and found further sign of a “background” of gravitational waves: invisible yet extremely fast ripples in space that can aid in unlocking some key mysteries of the universe.

The three studies offer new insights into the cosmos’s largest black holes, how they shaped the cosmos, and the cosmic architecture they left behind. Dr. Matt Miles, lead author for two of the three papers and a researcher at OzGrav and Swinburne, says the research opens new avenues for understanding the cosmos that we live in. “Studying the background lets us tune into the echoes of cosmic events across billions of years,” explained Dr. Miles. “It reveals how galaxies, and the universe itself, have evolved over time.”

Unprecedented gravitational wave signal

The study revealed further evidence of gravitational wave signals originating from merging SMBHs, capturing a signal sturdier than similar global experiments, and in just 1,3^rd of the time. “What we’re seeing hints at a much more dynamic and active universe than we anticipated,” said Dr. Miles. “We know supermassive black holes are out there merging, but now we’re starting to ask: where are they, and how many are out there?”

Detailed gravitational wave maps with unexpected hotspots

Employing the pulsar timing array, the experts constructed a highly detailed gravitational wave map, improving upon existing techniques. This map exposed an intriguing anomaly—an unforeseen hotspot in the signal that suggests a probable directional bias. Rowina Nathan, lead author for one of the studies and a researcher at OzGrav and Monash University, says the map offers an unprecedented glimpse into the structure of our cosmos. “The presence of a hotspot could suggest a distinct gravitational wave source, such as a pair of black holes billions of times the mass of our sun,” said she. “Looking at the layout and patterns of gravitational waves shows us how our universe exists today and contains signals from as far back as the Big Bang. There’s more work to do to determine the significance of the hotspot we found, but this an exciting step forward for our field.”

Employing the MeerKAT radio telescope in South Africa, one of the world’s most sensitive and advanced instruments, the scientists constructed the MeerKAT Pulsar Timing Array and used it to observe pulsars and time them to nanosecond precision. Pulsars—hastily spinning neutron stars—serve as natural clocks, and their steady pulses let scientists to detect minuscule changes caused by passing gravitational waves. This galactic-scale detector has offered an opportunity to map gravitational waves across the sky, baring patterns and variations that challenge earlier assumptions.

Rowina says it’s very often assumed that the gravitational wave background will be consistently distributed across the sky. “However, the galactic-sized gravitational wave detector formed by the MeerKAT pulsar timing array has allowed us to map the structure of this signal with unprecedented precision, which may reveal insights about its source.” These measurements open up stirring new questions about the formation of massive black holes and the early history of the cosmos. Continued observations with the MeerKAT array will refine these gravitational wave maps and may expose new, previously hidden cosmic phenomena.