In their eager search of gravitational waves, scientists spent over 6000 hours of research to spot the existence of these "hums" from possible neutron stars that emit them.
In their study, "Deep exploration for continuous gravitational waves at 171-172 Hz in LIGO second observing run data," researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at the Australian National University, trained their sights and ears towards a specific location in space trying to sense gravitational waves, which are ripples in the fabric of time and space, from rotating neutron stars.
Searching for Continuous Gravitational Waves at a Specific Location
These Australian researchers took an educated guess at this specific location, assuming they would hear the faint hums of continuous gravitational waves. They, however, knew that they could just be hearing radio waves from neutron star-like pulsars, but they still hung on waiting for that elusive hum, hypothesizing that there could be continuous gravitational waves spotted near pulsar radio waves.
Yet, while their search that involved existing observational data, spending 6000 hours of research using graphical processing units that extremely accelerated their algorithms, in waiting for that much anticipated "hum," researchers still ended up empty-handed.
Researchers said their search had been the most sensitive to date for the location they chose, but they said they didn't hear anything. They said they would still continue to stay in tune with that possible hum.
Hearing that Faint "Hum" of Gravitational Waves from Neutron Stars
Within the Universe, neutron stars are considered the densest objects, and if they are not spherical, they would emit that faint "hum" of constant gravitational waves.
Sensing this "hum" would let researchers to investigate deep within a neutron star and identify its secrets, getting a clear understanding of the most extreme states of matter. But the scientists' "ears", a observatories that use mirrors spaced four kilometers apart utilizing laser interferometry, called the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington and Louisiana in the US, have not heard anything.
This is because investigators remain uncertain of the ideal search method. Previous research entailed a "room-to-room" approach, identifying possible gravitational waves in as many locations as possible. This, however, would mean they would spend lesser time at a location to sense that "hum." Since such sound is very faint, researchers might not even hear it.
This led to Australian researcher trying to focus at one specific location for possible continuous gravitational waves despite the presence of pulsar radio waves, which has still yet to hear those hums.
Previous Detection of Gravitational Waves from Neutron Star Collisions
In 2017, observers from around the world detected continuous gravitational waves for the first time in history, National Geographic noted in an article. This was caused by the collision of two very dense neutron stars 130 million light-years away.
As the gravitational waves were heard, astronomers were alerted for the possible existence of signals, such as gamma rays, light, and radio waves from the phenomenon. This event revolutionized humanity's understanding of the Universe, opening up a specific scientific field wherein astronomers and gravitational wave scientists would collaborate.
A second detection of gravitational waves happened in 2019, with another merger of two colliding neutron stars, Astronomy Magazine said in an article. Only one of the LIGO detectors spotted the collision, preventing researchers to pinpoint the exact location of the event or if it emitted any light.
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