LIGO Can Probe the Cosmos for Exotic Gravitational Waves “Once Thought To Be Invisible”

 

Black-hole-event-wide

 

Researchers at the the Monash Centre for Astrophysics have identified a new concept – 'orphan memory' – which changes the current thinking around gravitational waves.


Einstein's theory of general relativity predicts that cataclysmic cosmic explosions stretch the fabric of spacetime. The stretching of spacetime is called 'gravitational waves.' After such an event, spacetime does not return to its original state. It stays stretched out. This effect is called 'memory.' The term 'orphan' alludes to the fact that the parent wave is not directly detectable.

 

"These waves could open the way for studying physics currently inaccessible to our technology," said Monash School of Physics and Astronomy Lecturer, Dr Eric Thrane, one of the authors of the study, together with Lucy McNeill and Dr Paul Lasky.

"This effect, called 'memory' has yet to be observed," said Dr Thrane. Gravitational-wave detectors such as LIGO only 'hear'' gravitational waves at certain frequencies, explains lead author Lucy McNeill. "If there are exotic sources of gravitational waves out there, for example, from micro black holes, LIGO would not hear them because they are too high-frequency," she said.

"But this study shows LIGO can be used to probe the universe for gravitational waves that were once thought to be invisible to it." Study co-author Lasky said LIGO won't be able to see the oscillatory stretching and contracting, but it will be able to detect the memory signature if such objects exist.

The researchers were able to show that high-frequency gravitational waves leave behind a memory that LIGO can detect. "This realisation means that LIGO may be able to detect sources of gravitational waves that no one thought it could," said Lasky.

A new view of a black hole event at top of the page via CERN ATLAS collision event. In some theories, microscopic black holes may be produced in particle collisions that occur when very-high-energy cosmic rays hit particles in our atmosphere. These microscopic-black-holes would decay into ordinary particles in a tiny fraction of a second and would be very difficult to observe in our atmosphere.

The ATLAS Experiment offers the exciting possibility to study them in the lab (if they exist). The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).

The Daily Galaxy via Monash University

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