2023-06-29 12:45:41
Scientists have found evidence of a cosmic background of gravitational waves, or ripples in the fabric of space-time, that span the entire universe.
The movement of black holes and other very massive objects through space can create ripples in the space-time fabric of the universe. These ripples, wrinkles, or distortions are commonly called gravitational waves. Now, a study that has analyzed data collected in observations over 15 years, reveals the first evidence of the existence of a background of long-wavelength gravitational waves that fills the cosmos. These waves are thought to have been created over billions of years by pairs of supermassive black holes, with masses up to billions of times that of our Sun, spinning ever closer around each other until colliding and merging into a just black hole. Detecting the cosmic background of gravitational waves is comparable to hearing the global hum of a large number of people talking at a party, without being able to distinguish any particular voice.
These waves oscillate very slowly over years and even decades.
The research is the work of the NANOGrav (North American Nanohertz Observatory for Gravitational Waves) initiative, which has received funding from the United States National Science Foundation (NSF), and in which more than 190 scientists from the United States and Canada. NANOGrav used data from radio telescopes (the Arecibo Observatory in Puerto Rico, the GBT (Green Bank Telescope) in West Virginia in the United States, and the VLA (Very Large Array) in New Mexico in the United States, to monitor 68 dead stars, of the type known as a pulsar, in the sky. The collection of pulsars served scientists as a kind of network of maritime buoys. Each pulsar was like a buoy that bobbed very slowly in a sea of gravitational waves instead of doing it fast in a ocean of water furrowed by waves.
Artist’s impression of a set of pulsars used as maritime buoys to detect the “swell” of the cosmic background of gravitational waves. (Image: Aurore Simonnet for the NANOGrav Collaboration)
When gravitational waves travel through the cosmos, they slightly stretch and compress the fabric of space-time. This combination of stretching and compression can cause the distance between Earth and a given pulsar to change only slightly, causing delays or gains in the timing of the pulsars’ flashes of light.
“The effect of gravitational waves on pulsars is extremely weak and difficult to detect, but we have been confident in the results as we collect more data,” explains Katerina Chatziioannou, from the California Institute of Technology (Caltech) in the United States and a member of the from the NANOGrav team.
Gravitational waves were first proposed by Albert Einstein in 1916, but were not directly detected until about a hundred years later, when the LIGO observatory captured the waves coming from a pair of distant colliding black holes. LIGO detects gravitational waves of much higher frequency than those recorded by NANOGrav.
High-frequency gravitational waves come from pairs of black holes with masses similar to those of stars, which rotate rapidly around each other in the last few seconds before colliding, while low-frequency waves are thought to be generated by huge holes. black in the heart of galaxies. Each of these very large black holes has a mass that is typically between a million and several billion times that of our sun.
NANOGrav detects low frequency gravitational waves, that is, with a cycle every few years.
The European Space Agency (ESA), with the help of its American counterpart, NASA, is preparing a space observatory that will be able to detect gravitational waves that are in a range of frequencies between those detected by NANOGrav and those detected by by LIGO. (Source: NCYT from Amazings)
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