Discovering gravitational waves from huge black hole crash using pulsars

James Marshall
November 14, 2017

But the mechanics at play to create gravitational waves during a supermassive black hole merger will work in more or less the same way as these miniature collisions. All of those events have been of much smaller black holes, of more like 30 times the size of our sun.

This isn't the sort of event we'll be able to hear with the super-sensitive long-distant hearing devices, the Laser Interferometer Gravitational-Wave Observatory (LIGO) that has so far spotted four examples of black holes merging since February 2016.

Now available pulsar timing arrays were sufficient to reveal gravitational waves in fewer than 1% of probabilistic simulations based on these local sources, which helps explain the lack of positive results obtained so far. These waves, being much stronger, have a far lower frequency than the gravitational waves that have been observed so far, which is why they can not be detected by human-made instruments.

Joseph Lazio, co-author of the study said that perceiving low-frequency gravitational waves would be related to being able to perceive bass singers, not just sopranos.

The researchers say pulsars are key to tapping into the songs of these intergalactic Barry Whites. These gravitational waves are caught by the ever emitting pulsars.

These pulsar timing arrays are based on the same principle as LIGO and Virgo. While the black holes will still merge, it may do so at an extended time that energy to produce a detectable gravitational wave is lost. Importantly, this method could be more tuned towards lower frequency waves.

Writing in Nature Astronomy, Chiara Mingarelli of the Max Planck Institute for Radio Technology in Germany, and California Institute of Technology in the United States, and a multi-institutional collaboration have calculated the likelihood of such an SMBHB being detected against the gravitational-wave background under a range of possible conditions.

The study, titled "The local nanohertz gravitational-wave landscape from supermassive black hole binaries", appeared online Monday in the journal Nature Astronomy. These monsters lurk at the center of many galaxies, and so their collisions might mark the grand finale of two galaxies merging into one.

Detecting the merging of two supermassive black holes will provide scientists a deeper understanding of how black holes and galaxies change over time. A new research predicts that a collision of two supermassive black holes will generate gravitational waves.

The researchers hope that the array can also teach us about how galaxies are formed and what happens when they merge - which could be useful information, considering we're now on-course for a collision with our neighboring Andromeda galaxy.

But if all goes well, the team even has a prediction of where the collision is most likely to take place: In a neighborhood like the Sombrero Galaxy, where a slightly less massive supermassive black hole means the collision would happen more slowly, leaving scientists more time to spot its signature. Thus, the merger of two black holes in Sombereo Galaxy took 160 million years, while M87, which was a larger galaxy, took 4 million years.

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