Einstein was right: first whisper of the Big Bang in space-time heard for the first time

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The Big Bang is currently the best model available to mankind to try to understand the history and first instants of the universe. It is strongly reinforced by numerous experimental observations, accompanied by constant predictions and challenges to test its veracity. Despite the severe limitations of current technology, humanity finds ways to take advantage of its environment to understand its surroundings. By combining a series of pulsars, astronomers have turned the Milky Way into a large gravitational wave detector to listen to the murmur of the beginning of the universe.

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Waves in the sea of space-time

Albert Einstein's theory of general relativity models gravity as the mutual interaction between matter and the so-called space-time. The latter defines how mass must behave and the trajectory that light must follow when moving. However, when large concentrations of material are involved, large disturbances appear in the tissue and produce so-called gravitational waves.

In 2015 the LIGO team confirmed the first detection of gravitational waves produced by the collision of two black holes, almost a hundred years since they were predicted. However, the equipment employed was limited to only being able to hear those of high frequency. If the same method were to be used, a laser of considerably larger dimensions than currently possible would be required, so an alternative was needed.

NanoGrav: using the galaxy as a mega gravitational wave detector

To study the first moments of the Big Bang we were limited to the electromagnetic radiation that makes up what is known as the microwave background, a faint, long-wavelength signal that permeates the entire universe. But the models predicted the possible existence of a much older signal, a series of gravitational waves that could have escaped from the primordial plasma and escaped to the rest of the universe.

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Graphical representation of the location of the pulsars used in the study (blue stars) with respect to the position of the Sun (yellow star). Credits: NANOGrav

NANOGrav seeks to detect gravitational waves with frequencies on the order of nanohertz, hence its name. To do so, they used a sample of approximately seventy pulsars in the Milky Way. These are stars of mass slightly greater than that of the Sun that have run out of fuel, but their remnant spins at enormous speeds and emits pulses at a constant rate. These act similar to a buoy in the ocean, where gravitational waves are waves that generate perturbations in their emission patterns.

Using several radio telescopes and data collected over fifteen years, the researchers studied the light patterns in pairs of pulsars each month. They compared the difference between the recorded light arrival times and the theoretical time. The latter was known with a high time resolution.

Researchers succeeded in measuring for the first time the fingerprints of collisions between high-mass black holescomparable to millions of suns compacted into a single object.. Which, unlike the LIGO point detections, numerous murmurs were found coming from all directions.

 

Francisco Andrés Forero Daza