New Technique Pinpoints Universe's First Gravitational Waves

Astronomers developed a method to detect gravitational waves dating back to the Big Bang.
Chris Young

As gravitational-wave astronomy is still a relatively new field, researchers are yet to advance far beyond observing powerful cosmic events that leave a huge gravitational footprint.

Black holes consuming each other and neutron stars exploding are two examples detected by researchers in recent times.


Underneath all of that noise, however, there is a different type of wave called a primordial gravitational wave that could unveil the mysteries of the early universe.

Now, a group of astronomers released a paper in Physical Review Letters that outlines their method for detecting these waves amidst the tremendous noise of clashing stars.


Ghosts of the cosmic past

Primordial gravitational waves were formed during the big bang. They have faded in intensity over more than 13 billion years, but they are still there, faintly detectable.

As these gravitational waves are so faint, most of the effort to detect them has focused on the way that they affect light, Universe Today writes.

According to the standard model of cosmology, primordial gravitational waves should slightly twist the orientation of light as it travels through space.

As such, light from the cosmic microwave background (CMB) should have a B-mode polarization. The problem, however, is that other space materials, such as dust, can also cause a B-mode polarization in the CMB. It's easy to confuse the two.

The research group, led by Sylvia Biscoveanu, a graduate student in MIT's Kavli Institute for Astrophysics and Space research, believes they have found a method to detect gravitational waves directly.

Sifting out primordial gravitational waves

The team's process involves removing the loud signals in a similar fashion to post-editing in sound recording, whereby a sound will be removed after the fact.

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The team created a model of an average overall signal from events such as black hole and supernovae mergers. Removing this from the gravitational wave data, the researchers were still left with noise caused by random fluctuations of the gravitational wave detector itself.

The researchers proposed comparing noise data from multiple gravitational wave observatories, each of which emits different noise. The team will then remove all of the noise that isn't common between these observatories.

In doing so, the astronomers believe they should be able to pick up the same primordial wave signal across all of these observatories. 

Though the researchers have shown their method can work in simulations, today's gravitational wave observatories simply aren't advanced enough for the method to work.

As new, more sensitive observatories come online, however, the method will likely be used in attempts to detect primordial gravitational waves. If the method works, it would give the scientific community a brilliant opportunity to test some of its hypotheses on the big bang and the beginning of the universe.

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