A galactic-scale gravitational wave detector has produced new maps of the universe

Gravitational waves, which are perturbations of the very fabric of space-time due to the acceleration of massive objects, were detected for the first time in September 2015. The discovery was considered a scientific milestone and was added to the list of evidence to date. favor of the theory of general relativity postulated 100 years earlier by Albert Einstein. Now, seven years after the readings began, a team of scientists led by Swinburne University of Technology has created the most detailed maps of gravitational waves in the observable universe.

The gravitational waves detected on September 14, 2015 were the result of the collision of two black holes. One was approximately 36 solar masses and the other 29. This event occurred about 1.3 billion light years from Earth. But black hole collisions are not the only events that cause gravitational waves. The collision of neutron stars and events in the distant (or early) universe can also cause them, for example. As detection methods become more sensitive, new sources will be discovered.

Mapping gravitational waves in a general way required thinking about new ways of observing. Traditionally they are detected locally through laser interferometers that measure the distortion of space-time. For their new maps, the scientists devised a galactic-scale detector based on the same concept as interferometers, although using radio measurement instruments.

This gravitational wave detector is the largest in history. It takes advantage of the MeerKAT radio telescope network in South Africa and most notably takes advantage of the behavior of pulsars. Pulsars are a type of neutron star, which are the remains of a massive star that exploded as a supernova. Pulsars emit electromagnetic radiation in the form of regular pulses (hence their name). The new detection method times the signals emitted by pulsars. If a pulse reaches Earth with a minuscule change in its speed, then it has encountered a gravitational wave.

The background of gravitational waves

Thanks to this pulsar approach, experts found more evidence of the weak “background” of gravitational waves. In previous work, physicists have postulated that this background is the superposition of discrete gravitational waves caused by cosmic events throughout time and space. To explain the concept, the analogy of the tranquility of the sea is used. From afar, the ocean seems like a peaceful place, but if you look closely, you can see that its surface is always in motion.

For Australian researchers, that slight movement recorded by their gravitational wave detector suggests that the universe is much more dynamic than expected. Gravitational waves arise from highly energetic cosmic collisions, such as the merger of supermassive black holes. That faint background of waves recorded from the pulsars could be a warning that these crashes are not unusual.

Unexpected “hot” spots appeared on the generated maps, suggesting the presence of colossal objects never before recorded. “The dots may suggest a different source of gravitational waves, such as a pair of black holes billions of times the mass of our Sun,” Rowia Nathan explained.one of the authors of the work.

The study included scientists of various nationalities, but was led by astronomers from Swinburne University of Technology, in Australia. According to lead author Matt Miles, the study will “tune into the echoes of cosmic events over billions of years and reveal how galaxies and the universe itself have evolved over time.”

“By looking for variations in the gravitational wave signal across the sky, we are looking for the fingerprints of the astrophysical processes that shape our universe,” said Kathrin Grunthal, co-author and researcher at the Max Planck Institute for Radio Astronomy.