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Gravitational Wave Search No Hum Drum Hunt – “Map to the Potential El Dorado of Gravitational Waves”

Artist’s impression of continuous gravitational waves generated by a spinning asymmetric neutron star. Credit: Mark Myers, Ozgrav-Swinburne University

Scientists are refining the search for puzzling continuous gravitational waves. The hunt for the never-before-heard ‘hum’ of gravitational waves caused by mysterious neutron stars just got a whole lot easier thanks to an international team of researchers.

Gravitational waves have only been detected from black holes and colliding neutron stars, large cosmic events that cause massive eruptions that ripple through space and time.

The research team, made up of scientists from the LIGO Scientific Collaboration (LSC), Virgo Collaboration and the Center for Gravitational Astrophysics (CGA) at the Australian National University (ANU), are now turning their eagle eye to spinning neutron stars to detect the waves.

Unlike the massive outbursts caused by black holes or colliding neutron stars, the researchers say some spinning neutron stars have a bulge or “mountain” only a few millimeters high, which can produce a steady constant stream or “hum” of gravitational waves. 

The researchers use their methods, which first detected gravitational waves in 2015, to capture this steady soundtrack from the stars above the thundering sound of massive black holes and dense neutron stars colliding.

They say it’s like trying to catch the squeak of a mouse in the middle of a stampeding herd of elephants.

If successful, it would be the first detection of a gravitational wave event that did not involve a collision of massive objects such as black holes or neutron stars.

ANU Distinguished Professor, Susan Scott of the ANU Research School of Physics, said the collision of dense neutron stars triggered a “burst” of gravitational waves rippling through the universe.

“Neutron stars are mysterious objects,” said Professor Scott, also principal investigator at the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav).

“We don’t really understand what they’re made of, or how many species there are. But what we do know is that when they collide, they send incredible bursts of gravitational waves across the universe.

” The soft hum of a spinning neutron star, on the other hand, is very faint. and nearly undetectable.

” Three new papers have just been published by the LSC-Virgo collaboration, detailing the most sensitive searches yet for the faint hum of gravitational waves from spinning neutron stars.

Their work provides a “map to the potential El Dorado of gravitational waves.” “One of our searches is focused on young supernova remnants.

These recently born neutron stars are more distorted and should emit a stronger stream of gravitational waves,” said Dr. Lilli Sun, of CGA and an Associate Investigator at OzGrav. As these searches become more sensitive, they provide more detail than ever about the possible shape and composition of neutron stars.

“If we manage to detect this buzz, we can look deep into the heart of a neutron star and unravel its secrets,” said Dr. Karl Wette, a postdoctoral researcher at OzGrav and the CGA.

Professor Scott, who is also the leader of the General Relativity Theory and Data Analysis Group at ANU, added: “Neutron stars represent the densest form of matter in the Universe before a black hole will form.

“By looking for their gravitational waves, we can investigate states of nuclear matter that simply cannot be produced in laboratories on Earth.”