2023-07-10 11:02:13
The NANOGrav collaboration has detected “a stochastic background of gravitational waves”
Just a few days ago, on June 29, the NANOGrav projectone of the largest international collaborations in history, made public a new discovery that, in the words of Nature, is set to “shake all astrophysics”. This physical advance has involved the work of thousands of scientists, distributed in dozens of centers around the world, and more than fifteen years of joint work collecting data. The statement was made during a live broadcast where it was announced that they had found evidence of a cosmic background of gravitational waves. The scientific article was published in The Astrophysical Journal Letters and, from there, the media launched into the now traditional race of publishing the discovery through rapid press releases and articles.
Discoveries in Frontier Physics are not easy to communicate. Scientific advances occur at a dizzying pace and certain fields, such as Astrophysics, are reaching levels of complexity that are beyond the knowledge of a general public. For this reason, it is more and more frequent that, days after the appearance of a news item, the main scientific magazines and websites also publish an article, more informative and simplified, trying to explain what this new discovery consists of or what implications it offers. This is the case of Nature, which first published the news about gravitational waves and, the next day, he offered a text clarifying points and explaining why it is an important advance. Similarly Space.com has also published a informative article.
In short, news in the media is a speed race to publish any news before anyone else, fortunately, to deepen and clarify that news days later. It is in these “second news” that patient readers often understand the true meaning of the discovery. And if we want to better understand the NANOGrav announcement, we must go back in time almost a century and return to the typical phrase of “Einstein was right”.
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After relativistic theories, the Universe is usually understood as a kind of smooth sheet, an elastic canvas that is deformed by the mass of objects. Physicists, Einstein included, have wondered for decades what would happen to that great trampoline we call space-time fabric if very massive events occurred, such as the collision of two gigantic stars or if two black holes with enormous masses collided. will merge. Spacetime conforms to these undulations, and Einstein predicted that the interaction of very massive objects would cause gravity waves, in the same way as if we were to throw a stone into a calm pond. These gravitational waves, produced by the deformation of the space-time fabric, would move like waves and, with the right instruments, we could detect them.
In 2016, a century after Einstein published his general theory of relativity, the experiment LIGO made the most anticipated announcement. It was February 11, at 4:30 p.m. David Reitzer, executive director of the LIGO experiment, was smiling on the press room and with a leisurely tone he smiled the following words: “Ladies and gentlemen, we have detected gravitational waves… we have succeeded”. 1.3 billion years ago, a pair of huge black holes collided, merged into one sun, and released a huge amount of energy that wobbled the fabric of space-time. LIGO’s laser interferometers are so advanced that they detect even the slightest movement on that cosmic flat sheet. Their lasers act like floating buoys and were able to detect ripples in space-time produced by the waves created by the “giant rocks of the black hole mass”…
It was a special moment for physics. That announcement opened the doors to a new way of looking at (or rather, listening to) the Cosmos. Most of the knowledge we have of the Universe we have acquired by analyzing the light from stars, galaxies… now, thanks to gravitational waves, we have another way of understanding the nature of great cosmic phenomena. Which brings us to today’s announcement made by NANOGrav.
We have done it again… we have detected gravitational waves again. But there are two important things: this timethe different waves and the method used is also new and amazing.
In 2016 the detection came from a specific event, two black holes merging, releasing energy and emitting a large gravitational wave. In the NANOGrav ad the authors speak of a “cosmic background of gravitational waves”, a hum, a symphony even. Supermassive black holes, quasars releasing energy, entire galaxies colliding with one another, making the fabric of space and time vibrate and creating a “gravitational clamor that runs through the Universe”.
And how have they detected it? Here comes another genius of the NANOGrav project because, instead of using laser instruments like in LIGO, what they have done is use data accumulated over 15 years from pulsar stars.
Artistic recreation of a pulsar star NASA
Pulsars are highly magnetized neutron stars spinning so fast and so precisely that physicists poetically call them “the beacons of the Universe.” These stars can turn on themselves hundreds of times per second., emitting pulses of light so exact that when they were discovered many thought they were signs of some extraterrestrial civilization. Thanks to their accuracy these cosmic lighthouses can also be used as “universal watches” and this quality is what the NANOGrav physicists have taken advantage of to detect tiny variations that are consistent with the emission of a gravitational wave.
“The NANOGrav team has created, in essence, a galactic scale detector that reveals the gravitational waves that pervade our universe.” explains the director of the NSF, Sethuraman Panchanathan. In the headline of this article it said that physicists are excited, and it is not for less: we are facing a fascinating advance in Astrophysics, a discovery that brings us closer to a global understanding of the great physical phenomena of the cosmos.
More interesting articles and news about the Universe on Yahoo:
Scientific references and more information:
Castelvecchi, David. «Giant Gravitational Waves: Why Scientists Are so Excited». Nature (2023) DOI:10.1038/d41586-023-02203-6.
Robert Lea “The universe is humming with gravitational waves. Here’s why scientists are so excited about the discovery” Space.com
Agazii, Gabriella, et al. «The NANOGrav 15 Years Data Set: Evidence for a Gravitational-Wave Background». The Astrophysical Journal Letters (2023), DOI: 10.3847/2041-8213/acdac6.
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#detection #gravitational #waves #interesting