#laser interferometer gravitational wave observatory

[tenth-sentence]

Laser light simultaneously shot down vacuum tunnels inside each tube, and reflected back by highly polished mirrors, is used to measure the relative length of each to fantastic accuracy.

"The Fabric of the Cosmos" - Brian Greene

[xtruss]

Scientists Discover Long Theorized 'Low Hum' Created by Supermassive Black Holes

Scientific theories surrounding gravitational wave background signals may provide clues about the earliest days of the universe.

An international team of astronomers has discovered a faint hum that permeates the universe and will provide them clues about supermassive black holes, colliding galaxies and possibly the Big Bang.

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) published a study on Wednesday showcasing evidence of the long theorized but never proven gravitational wave background (GWB) noise, a type of signal they believe emanates from supermassive black holes and colliding galaxies and may contain traces of the gravitational ripples caused by the Big Bang.

Four of the study’s six papers were published in the Astrophysical Journal Letters, the remaining two have been accepted for publication at a later date. The discovery was first made in 2021, but the culmination of their work is just now being published.

‘Humming Universe’: Hint of Gravitational Wave ‘Background’ Detected As Study Probes Cosmic Mystery! visual of gravitational waves from two converging black holes is depicted on a monitor behind Laser Interferometer Gravitational-Wave Observatory (LIGO) Co-Founder Kip Thorne as he speaks to members of the media following a news conference at the National Press Club in Washington, Thursday, Feb. 11, 2016. © AP Photo/Andrew Harnik

While GWB had been theorized before, no direct evidence had been found until now.

Gravitational waves themselves are also technically a recent discovery. While they were first described in Einstein’s 1915 Theory of General Relativity, they had not been detected until 2015.

While every piece of matter in the universe emits gravitational waves - most of them are undetectable - scientists can only hope to observe the effects of some of the largest bodies in the universe.

That finally happened when the Laser Interferometer Gravitational-wave Observatory (LIGO) detected them for the first time in 2015. The LIGO shoots lasers down three-mile-long perpendicular tubes, with the hope that a gravitational wave will pass over it, causing one laser to shrink slightly while the other grows.

Started in 1994 and first completed in 1997, the LIGO cost $395 million to build and didn’t detect any waves for the first 10 years of its existence. It shut down temporarily for a $200 million upgrade and renovation before finally detecting a gravitational wave that scientists believe came from two black holes, roughly 30 times the size of the sun each, colliding about 1.3 billion light-years from Earth.

But LIGO is not capable of detecting GWB created by super massive black holes, which range from 100,000 to six billion times the size of the sun.

So instead, the scientists at NANOGrav looked to the stars, or more specifically pulsars.

Pulsars are dead stars, also known as neutron stars, that are highly magnetic and rotate roughly 700 times a second. Their spin is incredibly consistent and looks like flickering when observed from Earth. They are sometimes compared to lighthouses or clocks because of their consistency.

The NANOGrav astronomers watched pulsars for 15 years across different observatories in West Virginia, Puerto Rico, New Mexico and Canada, waiting for tiny variations that would indicate a gravitational wave from a supermassive black hole.

They were able to distinguish the signal from other gravitational waves because of the pattern it passed through the pulsar. GWBs are unique from other gravitational waves because they come so close together they overlap. The researchers describe it by comparing it to hearing a crowd of people talking at once. At first, it sounds like a low consistent hum, until you concentrate and can pick out specific conversations.

The same became true of GWBs once astronomers were able to detect the tiniest variations. Officials say they could predict the pulses from the pulsars down to 1 microsecond, the equivalent of measuring the distance of the moon within a thousandth of a millimeter.

“We are extraordinarily excited to see this pattern pop out finally,” said Stephen Taylor, a gravitational wave astrophysicist at Vanderbilt University, who co-led the research.

While scientists aren’t positive about the source of the GWB, it mirrored theories about the types of gravitational waves thought to be created by supermassive black holes.

Scientists also say the rate of the waves is increasing, suggesting there may be hundreds or even thousands of supermassive black holes that have not yet been discovered. The signals may help us discover where some of these objects are and how they work, as well as provide scientists clues into the formation of galaxies and even the universe.

Gravitational Waves May Be Generated From Debris Fields Around Dying Stars — Study June 7, 2023!

Scientists previously feared supermassive black holes would never collide and just continually orbit each other; this was called the “final parsec problem” in the astrophysicist community.

“To get these types of high amplitudes that we are seeing, we need fairly massive black holes, and they need to form binaries [aka supermassive black holes] quite frequently and evolve quite efficiently,” Luke Zoltan Kelley, an assistant professor at the University of California, Berkeley who participated in the NANOGrav study, said in a statement.

He adds if it is confirmed that the waves came from a supermassive black hole, “then they absolutely had to have passed the final parsec one way or another.”

— Ian DeMartino, Sputnik International, Wednesday June 28, 2023

[mysticstronomy]

CAN TWO SUPERMASSIVE BLACK HOLES MERGE??

Blog#440

Saturday, September 28th, 2024.

Welcome back,

A team of astrophysicists that includes the University of Toronto’s Gonzalo Alonso-Álvarez has shown that pairs of supermassive black holes can merge together into a single, larger black hole – a major breakthrough in addressing what is known as the "final parsec problem."

longstanding astrophysics problem refers to a discrepancy between the detection of gravitational signals permeating the universe – which astrophysicists previously hypothesized had emanated from millions of merging pairs of supermassive black holes (SMBHs) – and theoretical simulations which showed that the approach of SMBHs stalls when they’re roughly one parsec (about three light years) apart.

Not only did the final parsec problem conflict with the theory that merging SMBHs were the source of the gravitational wave background, it was also at odds with the theory that SMBHs – each billions of times more massive than our Sun – grow from the merger of less massive black holes.

The new research, published in Physical Review Letters, has shown that pairs of SMBHs can indeed break through the one-parsec barrier and merge into a single black hole. This is demonstrated by calculations showing that SMBHs continue to draw closer because of previously overlooked interactions with particles within the vast cloud of dark matter surrounding them.

“We show that including the previously overlooked effect of dark matter can help supermassive black holes overcome this final parsec of separation and coalesce,” says Alonso-Álvarez, a post-doctoral fellow in the department of physics at U of T’s Faculty of Arts & Science and the department of physics and Trottier Space Institute at McGill University, who is first author on the paper. “Our calculations explain how that can occur, in contrast to what was previously thought.”

SMBHs are thought to lie in the centres of most galaxies. When two galaxies collide, the SMBHs fall into orbit around each other; as they revolve around each other, the gravitational pull of nearby stars tugs at them and slows them down, causing them to spiral inward toward a merger.

Previous merger models showed that when the SMBHs approached to within roughly a parsec, they begin to interact with the dark matter cloud or halo in which they are embedded. These models indicated that the gravity of spiraling SMBHs throws dark matter particles clear of the system.

The new model introduced by Alonso-Álvarez and co-authors James Cline, a professor at McGill University and the European Organization for Nuclear Research (CERN) in Switzerland, and Caitlyn Dewar, a graduate student at McGill, reveals that dark matter particles interact with each other in such a way that they are not dispersed. The density of the dark matter halo remains high enough that interactions between the particles and the SMBHs continue to degrade the SMBH’s orbits – clearing a path to a merger.

“The possibility that dark matter particles interact with each other is an assumption that we made, an extra ingredient that not all dark matter models contain,” says Alonso-Álvarez. “Our argument is that only models with that ingredient can solve the final parsec problem.”

The background hum generated by these colossal cosmic collisions is made up of gravitational waves of much longer wavelength than those first detected in 2015 by astrophysicists operating the Laser Interferometer Gravitational-Wave Observatory (LIGO).

Those gravitational waves were generated by the merger of two black holes, both some 30 times the mass of the Sun.

The background hum has been detected in recent years by scientists operating the Pulsar Timing Array. The array reveals gravitational waves by measuring minute variations in signals from pulsars, rapidly rotating neutron stars that emit strong radio pulses.

Originally published on https://www.utoronto.ca

COMING UP!!

(Wednesday, October 2nd, 2024)

"WHERE DID MARS' ATMOSPHERE GO??"

[wonders-of-the-cosmos]

BlackGEM telescopes begin hunt for gravitational-wave sources at ESO's La Silla Observatory

The BlackGEM array, consisting of three new telescopes located at ESO’s La Silla Observatory, has begun operations. The telescopes will scan the southern sky to hunt down the cosmic events that produce gravitational waves, such as the mergers of neutron stars and black holes.

Some cataclysmic events in the Universe, such as the collision of black holes or neutron stars, create gravitational waves, ripples in the structure of time and space. Observatories like the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo Interferometer are designed to detect these ripples. But they cannot pinpoint their origin very accurately nor see the fleeting light that results from the collisions between neutron stars and black holes. BlackGEM is dedicated to quickly scanning large areas of the sky to precisely hunt down gravitational-wave sources using visible light.

Source

[spacetimewithstuartgary]

Origin of supermassive black hole Sagittarius A*

The origins of aptly named supermassive black holes – which can weigh in at more than a million times the mass of the sun and reside in the center of most galaxies – remain one of the great mysteries of the cosmos. 

Now, researchers from the Nevada Center for Astrophysics at UNLV (NCfA) have discovered compelling evidence suggesting that the supermassive black hole at the center of our Milky Way galaxy, known as Sagittarius A* (Sgr A*), is likely the result of a past cosmic merger. 

The study, published Sept. 6 in the journal Nature Astronomy, builds on recent observations from the Event Horizon Telescope (EHT), which captured the first direct image of Sgr A* in 2022. The EHT, the result of a global research collaboration, syncs data from eight existing radio observatories worldwide to create a massive, Earth-sized virtual telescope. 

UNLV astrophysicists Yihan Wang and Bing Zhang utilized the data from the EHT observation of Sgr A* to look for evidence on how it may have formed. Supermassive black holes are thought to grow either by the accretion of matter over time, or by the merger of two existing black holes. 

The UNLV team investigated various growth models to understand the peculiar rapid spin and misalignment of Sgr A* relative to the Milky Way’s angular momentum. The team demonstrated that these unusual characteristics are best explained by a major merger event involving Sgr A* and another supermassive black hole, likely from a satellite galaxy.

“This discovery paves the way for our understanding of how supermassive black holes grow and evolve,” said Wang, the lead author of the study and an NCfA postdoctoral fellow at UNLV. “The misaligned high spin of Sgr A* indicates that it may have merged with another black hole, dramatically altering its amplitude and orientation of spin.”

Using sophisticated simulations, the researchers modeled the impact of a merger, considering various scenarios that align with the observed spin properties of Sgr A*. Their results indicate that a 4:1 mass ratio merger with a highly inclined orbital configuration could reproduce the spin properties observed by the EHT. 

“This merger likely occurred around 9 billion years ago, following the Milky Way’s merger with the Gaia-Enceladus galaxy,” said Zhang, a distinguished professor of physics and astronomy at UNLV and the founding director of the NCfA. “This event not only provides evidence of the hierarchical black hole merger theory but also provides insights into the dynamical history of our galaxy.” 

Sgr A* sits at the center of the galaxy more than 27,000 light years away from Earth, and sophisticated tools like the EHT provide direct imaging that helps scientists put predictive theories to the test. 

Researchers say that the findings from the study will have significant implications for future observations with upcoming space-borne gravitational wave detectors, such as the Laser Interferometer Space Antenna (LISA), which is planned to launch in 2035 and is expected to detect similar supermassive black hole mergers across the universe.

[vital-deloin]

Atomic space and gravitational waves. On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) became the first observatory to detect gravitational waves on Earth. When two black holes, located about 1.3 billion light-years from Earth, merged, they created gravitational waves - ripples in space and time. The detected signal came from the merger of two giant black holes - with masses of 36 and 29 solar masses. Gravitational waves from their collision reached the LIGO detector, causing the distance between its mirrors, separated by 4 kilometers, to change by about 1/1000th the diameter of a proton. In the video, the proton's motion shows tiny changes measured by LIGO detectors. Video: LIGO Lab Caltech/MIT

[jamieroxxartist]

🎬 Watch The Television Show Trailer in the comments below:

Tuesday, Aug 27, 2024. Episode #1418 of 🎨#JamieRoxx’s www.PopRoxxRadio.com 🎙️#TalkShow and 🎧#Podcast w/ Featured Guest:

#ErinMacdonald (#PhD, #Astrophysics) is a #writer, #speaker, #producer, and #scienceadvisor, best known for her current work as the official science advisor for the #STARTREK franchise. Also Voice Actor on #StarTrekProdigy and the video game #StarTrekOnline.

Pop Art Painter Jamie #Roxx (www.JamieRoxx.us) welcomes Erin Macdonald (PhD, Astrophysics) is a writer, speaker, producer, and science advisor, voice Actress to the Show!

(Click to go there) ● WEB: www.erinpmacdonald.com ● IG: @drerinmac ( www.instagram.com/drerinmac ) ● IMDB: www.imdb.com/name/nm8574394

Erin Macdonald (PhD, Astrophysics) is a writer, speaker, producer, and science advisor, best known for her current work as the official science advisor for the STAR TREK franchise. She has also voiced her fictional counterpart in the Star Trek universe: Lt Cmdr Dr Erin Macdonald in Star Trek: Prodigy and the video game Star Trek Online. Known as “The Julia Child of Science,” as a science communicator Erin has appeared on NPR's Science Friday and Short Wave podcasts, provided commentary for numerous docuseries, and wrote and hosted the award-winning "Science of Star Trek" promotional videos for Paramount+. She wrote the baby board book "Star Trek: My First Book of Space" and wrote and narrated the Audible Original "The Science of Sci-Fi" in collaboration with The Great Courses.Prior to all of this work, she received her PhD at 25 at the University of Glasgow in Scotland and conducted research with the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration, but left shortly before their 2017 Nobel Prize-winning discovery of gravitational waves. She also has worked as a museum educator, community college professor, and Department of Defense systems engineering technical advisor. She received dual BA’s from the University of Colorado at Boulder in Physics with Astrophysics (cum laude ) and Mathematics. Through her company Spacetime Productions, she produces award-winning sci-fi films by LGBTQIA+ creators. Her most recent film IDENTITEAZE written and directed by Jessie Earl is available for streaming at go.nebula.tv/identiteaze.

● Media Inquiries: Annie Jeeves Publicist Cinematic Red PR cinematicred.com

[michaelgabrill]

NASA Reveals Prototype Telescope for Gravitational Wave Observatory

NASA has revealed the first look at a full-scale prototype for six telescopes that will enable, in the next decade, the space-based detection of gravitational waves — ripples in space-time caused by merging black holes and other cosmic sources. The LISA (Laser Interferometer Space Antenna) mission is led by ESA (European Space Agency) in partnership […] from NASA https://ift.tt/BeUP295

[newstein19]

What is LIGO ?

LIGO, the Laser Interferometer Gravitational-Wave Observatory, is a place where scientists detect gravitational waves. These waves are like ripples in space caused by big events, such as black holes colliding. LIGO uses lasers to measure tiny changes, helping us learn more about the universe. On the concept of LIGO the physicists are constructing the world's first Einstein's telescope ( on the borders of Germany, Belgium and Switzerland ) which will be using the concept of gravitational waves ( Proposed by Prof. Albert Einstein in his famous paper work on general relativity in the year 1915 ) to view astronomical events .

[whats-in-a-sentence]

With LIGO and its subsequent improvements,* we will view the cosmos in a completely new way.

* One of these is the planned Laser Interferometer Space Antenna (LISA), a space-based version of LIGO comprising multiple spacecraft, separated by millions of kilometers, playing the role of LIGO's four-kilometer tubes. There are also other detectors that are playing a critical role in the search for gravitational waves, including the German-British detector GEO600, the French-Italian detector VIRGO, and the Japanese detector TAMA300.

"The Fabric of the Cosmos" - Brian Greene

[spacenutspod]

2 min read NASA Reveals Prototype Telescope for Gravitational Wave Observatory NASA has revealed the first look at a full-scale prototype for six telescopes that will enable, in the next decade, the space-based detection of gravitational waves — ripples in space-time caused by merging black holes and other cosmic sources. On May 20, the full-scale Engineering Development Unit Telescope for the LISA (Laser Interferometer Space Antenna) mission, still in its shipping frame, was moved within a clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. NASA/Dennis Henry The LISA (Laser Interferometer Space Antenna) mission is led by ESA (European Space Agency) in partnership with NASA to detect gravitational waves by using lasers to measure precise distances — down to picometers, or trillionths of a meter — between a trio of spacecraft distributed in a vast configuration larger than the Sun. Each side of the triangular array will measure nearly 1.6 million miles, or 2.5 million kilometers. “Twin telescopes aboard each spacecraft will both transmit and receive infrared laser beams to track their companions, and NASA is supplying all six of them to the LISA mission,” said Ryan DeRosa, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The prototype, called the Engineering Development Unit Telescope, will guide us as we work toward building the flight hardware.” The prototype LISA telescope undergoes post-delivery inspection in a darkened NASA Goddard clean room on May 20. The entire telescope is made from an amber-colored glass-ceramic that resists changes in shape over a wide temperature range, and the mirror’s surface is coated in gold. NASA/Dennis Henry The Engineering Development Unit Telescope, which was manufactured and assembled by L3Harris Technologies in Rochester, New York, arrived at Goddard in May. The primary mirror is coated in gold to better reflect the infrared lasers and to reduce heat loss from a surface exposed to cold space since the telescope will operate best when close to room temperature. The prototype is made entirely from an amber-colored glass-ceramic called Zerodur, manufactured by Schott in Mainz, Germany. The material is widely used for telescope mirrors and other applications requiring high precision because its shape changes very little over a wide range of temperatures. The LISA mission is slated to launch in the mid-2030s. Download additional images from NASA’s Scientific Visualization Studio By Francis ReddyNASA’s Goddard Space Flight Center, Greenbelt, Md. Media Contact:Claire Andreoli301-286-1940claire.andreoli@nasa.govNASA’s Goddard Space Flight Center, Greenbelt, Md. Share Details Last Updated Oct 22, 2024 Related Terms Astrophysics Black Holes Galaxies, Stars, & Black Holes Goddard Space Flight Center Gravitational Waves LISA (Laser Interferometer Space Antenna) The Universe Keep Exploring Discover Related Topics Missions Humans in Space Climate Change Solar System

[the-telescope-times]

(via Uncanny Coincidence: Fast Radio Burst Detected After Gravitational Wave Event)

On the 25th of April in 2019, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) recorded a bright, non-repeating fast radio burst ( FRB).

Just 2.5 hours earlier, the Laser Interferometer Gravitational-Wave Observatory (LIGO) recorded a gravitational wave event, the collision as a binary neutron star reached the inevitable conclusion of its decaying orbit.

[mysticstronomy]

IS TIME INFINITE IN BLACK HOLES??

Blog#365

Wednesday, January 10th, 2024.

Welcome back,

The singularity at the center of a black hole is the ultimate no man's land: a place where matter is compressed down to an infinitely tiny point, and all conceptions of time and space completely break down. And it doesn't really exist. Something has to replace the singularity, but we're not exactly sure what.

Let's explore some possibilities.

It could be that deep inside a black hole, matter doesn't get squished down to an infinitely tiny point. Instead, there could be a smallest possible configuration of matter, the tiniest possible pocket of volume.

This is called a Planck star, and it's a theoretical possibility envisioned by loop quantum gravity, which is itself a highly hypothetical proposal for creating a quantum version of gravity.

In the world of loop quantum gravity, space and time are quantized — the universe around us is composed of tiny discrete chunks, but at such an incredibly tiny scale that our movements appear smooth and continuous.

This theoretical chunkiness of space-time provides two benefits. One, it takes the dream of quantum mechanics to its ultimate conclusion, explaining gravity in a natural way.

And two, it makes it impossible for singularities to form inside black holes.

As matter squishes down under the immense gravitational weight of a collapsing star, it meets resistance. The discreteness of space-time prevents matter from reaching anything smaller than the Planck length (around 1.68 times 10^-35 meters). All the material that has ever fallen into the black hole gets compressed into a ball not much bigger than this.

Perfectly microscopic, but definitely not infinitely tiny.

This resistance to continued compression eventually forces the material to un-collapse (i.e., explode), making black holes only temporary objects. But because of the extreme time dilation effects around black holes, from our perspective in the outside universe it takes billions, even trillions, of years before they go boom. So we're all set for now.

Another attempt to eradicate the singularity — one that doesn't rely on untested theories of quantum gravity — is known as the gravastar. It's such a theoretical concept that my spell checker didn't even recognize the word.

The difference between a black hole and a gravastar is that, instead of a singularity, the gravastar is filled with dark energy. Dark energy is a substance that permeates space-time, causing it to expand outward. It sounds like sci-fi, but it's real: dark energy is currently in operation in the larger cosmos, causing our entire universe to accelerate in its expansion.

As matter falls onto a gravastar, it isn't able to actually penetrate the event horizon (due to all that dark energy on the inside) and therefore just hangs out on the surface. But outside that surface, gravastars look and act like normal black holes. (A black hole's event horizon is its point of no return — the boundary beyond which nothing, not even light, can escape.)

However, recent observations of merging black holes with gravitational wave detectors have potentially ruled out the existence of gravastars, because merging gravastars will give a different signal than merging black holes, and outfits like LIGO (the Laser Interferometer Gravitational-Wave Observatory) and Virgo are getting more and more examples by the day. While gravastars aren't exactly a no-go in our universe, they are definitely on thin ice.

Originally published https://www.space.com/

COMING UP!!

(Saturday, January 13th, 2024)

"JUPITER HAS A LARGE MAGNETIC FIELD THAN PREVIOUSLY EXPECTED??"

[xtruss]

An Enormous Gravity ‘Hum’ Moves Through the Universe

Astronomers have found a background din of exceptionally long-wavelength gravitational waves pervading the cosmos. The cause? Probably supermassive black hole collisions, but more exotic options can’t be ruled out.

— By Jonathan O'Callaghan, Contributing Writer | Quantum Magazine | June 28th, 2023

The 100-meter Green Bank Telescope has precisely measured the timing of dozens of pulsars over the course of 15 years.

Astronomers have found an extra-low hum rumbling through the universe. The discovery, announced today, shows that extra-large ripples in space-time are constantly squashing and changing the shape of space. These gravitational waves are cousins to the echoes from black hole collisions first picked up by the Laser Interferometer Gravitational-Wave Observatory (LIGO) experiment in 2015. But whereas LIGO’s waves might vibrate a few hundred times a second, it might take years or decades for a single one of these gravitational waves to pass by at the speed of light.

The finding has opened a wholly new window on the universe, one that promises to reveal previously hidden phenomena such as the cosmic whirling of black holes that have the mass of billions of suns, or possibly even more exotic (and still hypothetical) celestial specters.

“It’s beautiful,” said Chiara Caprini, a theoretical physicist at the University of Geneva and CERN in Switzerland who was not directly involved in the work. “A new era in the observation of the universe has opened up.”

The results come from studies that stretch back more than a decade by four teams based in the U.S., Europe, Australia and China. Today, in a coordinated data release, the teams present evidence for a background “hum” of gravitational waves that were detected by tracking changes in the impossibly regular beats of objects called pulsars.

As long-wavelength gravitational waves pass through our cosmic neighborhood, they distort the space-time around us, which changes the arrival time of a pulsar’s pulses. Researchers had to map the correlations of these arrival times across dozens of different pulsars for decades in order to pick up the signal. “I had butterflies when I first saw this,” said Stephen Taylor, an astrophysicist at Vanderbilt University and chair of the team known as the North American Nanohertz Observatory for Gravitational Waves, or NANOGrav. “I’m so excited we can finally talk about it.”

The NANOGrav team primarily used three large radio observatories in North America (left to right): the Green Bank Telescope in West Virginia, the Very Large Array in New Mexico and the Arecibo Observatory in Puerto Rico. Green Bank Observatory; Susan E. Degginger/Science Source; David Parker/Science Source

Most likely, the gravitational waves come from pairs of supermassive black holes that are spiraling around each other inside merging galaxies. But we might be seeing something else entirely, perhaps something exotic such as ruptures in space-time itself resulting from loops of energy called cosmic strings.

“Finding for the first time the suggestion of background gravitational waves is fascinating,” said Juan García-Bellido, a theoretical cosmologist from the Autonomous University of Madrid who was not involved in the work. “It’s really Nobel Prize-winning research.”

A Galaxy-Size Hack

There’s two ways to start the story of this discovery. The first, as usual, is with Albert Einstein. His general theory of relativity in 1915 suggested that the universe is an ocean of space-time on which objects like black holes and stars sit. Movements of these objects would send ripples across this space-time ocean — gravitational waves.

The other place to start the story is in 1967, with a graduate student from Lurgan, Northern Ireland, named Jocelyn Bell. Using a radio telescope that she helped build near Cambridge, U.K., she spotted an unusual signal in space that repeated every second. She and other astronomers later classified these signals as a new class of celestial object known as pulsars — the rapidly spinning cores of dead stars. Today, some are known to spin exceedingly fast, emitting regular pulses of radio waves hundreds or even thousands of times per second.

The stopwatch-like regularity of pulsars makes them valuable cosmic timekeepers. In 1983, the U.S. astronomers Ron Hellings and George Downs suggested a novel way to put them to use: If gravitational waves were squeezing and stretching space-time, that motion would change the arrival time of the pulsars’ radio flashes.

The key is to look at many pairs of pulsars and compare their time delays. “If they’re close together on the sky, they’re both going to be early or late,” said Sarah Vigeland, an astrophysicist at the University of Wisconsin, Milwaukee and chair of NANOGrav’s Gravitational Wave Detection Working Group. “As you pull them apart, they become out of sync, but in a way you can predict.”

Merrill Sherman/Quanta Magazine; source: nanograv.org

To catch these fluctuations, pulsar timing arrays such as NANOGrav use multiple radio telescopes to observe many pulsars over many years. These projects are cosmic cousins of LIGO and other earthbound observatories that detect gravitational waves by looking for tiny changes in the relative lengths of its two arms.

While LIGO’s arms are each four kilometers long, pulsar timing arrays effectively use the distance from Earth to each pulsar as a much larger arm — one hundreds or thousands of light-years in length. “What we’ve essentially done is hack the entire galaxy to make a giant gravitational wave antenna,” Taylor said.

This longer distance makes pulsar timing arrays sensitive to a different variety of gravitational wave. Whereas LIGO can detect high-frequency gravitational waves, which might occur when star-size black holes orbit each other tens or hundreds of times a second before merging, pulsar timing arrays are sensitive to processes occurring across years or even decades. That’s one reason why pulsar timing arrays need many years of data — if it takes a decade for a single wave to pass by, you can’t detect it in just a few months.

Of the four groups releasing data today, NANOGrav is the most confident in its result. The project was founded in 2007 and has largely used the Green Bank Telescope in West Virginia and the Arecibo radio telescope in Puerto Rico (which collapsed in late 2020, near the end of NANOGrav’s 15 years of data collection). “We’re still mourning the loss of Arecibo,” Taylor said.

Separate pulsar timing array projects were also established in different parts of the globe. The four teams, which together form the International Pulsar Timing Array, coordinated today’s announcements, but they have not yet performed a combined data analysis. “It’s complex,” said Andrew Zic, an astronomer at the Commonwealth Scientific and Industrial Research Organization in Australia and part of that country’s Parkes Pulsar Timing Array team. “We’re ready to move towards being a more unified thing.”

In 2020, NANOGrav released preliminary data from 12.5 years of observations. Those showed a tentative hint of gravitational waves affecting the pulses of some 45 pulsars.

Now they’ve added a few more years of data, along with data from nearly two dozen more sources, and a more consistent pattern has emerged. “It really jumps out to us,” Vigeland said.

“We’re looking at deviations in time that are a couple of hundred nanoseconds,” said Scott Ransom, an astronomer at the National Radio Astronomy Observatory and a founding member of NANOGrav. They’ve detected a particular pattern in the data, called the Hellings-Downs curve, that makes them confident that what they’re seeing is the gravitational-wave background. “That’s the smoking gun of gravitational waves.”

The European team, which observed 25 pulsars over 25 years with six telescopes, sees similar hints of timing delays but is less certain of their results. “The Americans are very confident,” said Michael Keith, an astrophysicist at the Jodrell Bank Center for Astrophysics and part of the European team. The Australian team is reporting observations from 32 pulsars over 18 years, while the Chinese team has observed 57 pulsars for a little more than three years.

Supermassive Dances

So what’s causing these waves? The most likely sources are supermassive black holes — behemoths millions to billions of times the mass of our sun. These are found at the center of massive galaxies such as our own Milky Way. When two galaxies collide, as sometimes happens, the supermassive black holes at their centers may also begin to orbit each other, twirling around at a cosmically ponderous rate, and perturbing space-time as they do.

“If you have a rotating distribution of mass that’s not symmetric” — even something small, like a spinning pen — “gravitational waves are coming out,” Keith said. On big enough scales, with supermassive black holes, the low and steady rumble of these waves becomes detectable as they permeate space.

Sarah Vigeland, an astrophysicist at the University of Wisconsin, Milwaukee, and chair of NANOGrav’s Gravitational Wave Detection Working Group, is one of more than 190 researchers working on NANOGrav. Tonia Klein

NANOGrav can’t yet make out individual gravitational wave sources. Instead, the team has found evidence for the background hum of all low-frequency gravitational waves. It’s like a buoy bouncing up and down in a busy harbor — it can’t distinguish the wake of a single boat, but its motion can reveal that there are some big objects slicing through the water.

Supermassive black holes, however, are not the only possible explanation for the background hum. Another possibility is cosmic strings. First predicted in the 1970s, these would essentially be cracks in space-time caused by the expansion of the universe. The cracks would emit gravitational waves as they spun around in loops.

“The idea of cosmic strings is you have some extension of the Standard Model [of particle physics] in which, in addition to pointlike particles, you can get strings of energy stretching out across the universe,” said John Ellis, a theoretical physicist at King’s College London and CERN who is a proponent of cosmic strings. “Those strings of energy move around and can collide, spawning loops of string that eventually collapse by emitting gravitational waves.”

While the idea is somewhat extravagant, the observations so far from NANOGrav and the other teams are consistent with what we’d expect to see from cosmic strings. “They’d be constantly wriggling, and from time to time they crack like a whip and send out gravitational wave bursts,” said Patrick Brady, an astrophysicist at the University of Wisconsin, Milwaukee. If the pulsar timing arrays don’t see individual sources start to emerge from their upcoming data, that could point toward this exotic physics beyond the Standard Model. “Cosmic strings will give you a much smoother signal,” Ellis said.

But while strings and other exotic phenomena can’t be ruled out, for now supermassive black holes are the favored explanation. “From an Occam’s razor point of view, we know galaxies merge and almost all galaxies have supermassive black holes,” Ransom said. “So we think it’s probably most likely that the signal we’re seeing is from supermassive black holes. But we could be wrong.”

Discovering a population of supermassive black hole pairs would help answer open questions in astrophysics. For example, what happens when two orbiting supermassive black holes get relatively close to each other? There were reasons to think that instead of merging, as smaller black holes do, supermassive black holes just rotate around each other forever. “This is called the last-parsec problem,” Caprini said; a parsec is a unit of distance measuring 3.26 light-years across. “It is an unsolved problem.” If pulsar timing arrays are seeing gravitational waves from these moments, however, it would be “a demonstration that two supermassive black holes do get close enough and merge,” rather than remaining in distant orbits, Caprini said.

Just the existence of such a population has broad implications for our understanding of galactic evolution in the universe. “It would mean that at the center of some galaxies, there are massive black holes that are not just alone,” Caprini said. “We can probe, through the history of the universe, how galaxies collide and the rate of collisions.”

Such work would require the discovery of individual supermassive black hole pairs, and so is not yet feasible. But as researchers combine the data sets from the different teams and take more observations over the next few years, individual sources may start to emerge, perhaps allowing astronomers to pinpoint binary supermassive black holes in space and time.

“Bright individual sources will start poking above this background hum,” said Maura McLaughlin, an astrophysicist at West Virginia University and one of the founding members of NANOGrav. “We’ll be able to say, in that direction, there is a supermassive black hole binary with [a certain] mass. We’ll learn a whole lot about galaxy mergers.”

What is clear is that these projects have given astronomers a completely new tool with which to study the cosmos. The rise of gravitational-wave astronomy “is like when Galileo first turned his telescope on the sky,” Brady said. We now know that a background of ripples in space-time pervades the universe. An ocean of gravitational waves awaits.

[spacetimewithstuartgary]

NASA reveals prototype telescope for gravitational wave observatory

NASA has revealed the first look at a full-scale prototype for six telescopes that will enable, in the next decade, the space-based detection of gravitational waves — ripples in space-time caused by merging black holes and other cosmic sources.

The LISA (Laser Interferometer Space Antenna) mission is led by ESA (European Space Agency) in partnership with NASA to detect gravitational waves by using lasers to measure precise distances — down to picometers, or trillionths of a meter — between a trio of spacecraft distributed in a vast configuration larger than the Sun. Each side of the triangular array will measure nearly 1.6 million miles, or 2.5 million kilometers.

“Twin telescopes aboard each spacecraft will both transmit and receive infrared laser beams to track their companions, and NASA is supplying all six of them to the LISA mission,” said Ryan DeRosa, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The prototype, called the Engineering Development Unit Telescope, will guide us as we work toward building the flight hardware.”

The Engineering Development Unit Telescope, which was manufactured and assembled by L3Harris Technologies in Rochester, New York, arrived at Goddard in May. The primary mirror is coated in gold to better reflect the infrared lasers and to reduce heat loss from a surface exposed to cold space since the telescope will operate best when close to room temperature.

The prototype is made entirely from an amber-colored glass-ceramic called Zerodur, manufactured by Schott in Mainz, Germany. The material is widely used for telescope mirrors and other applications requiring high precision because its shape changes very little over a wide range of temperatures.

The LISA mission is slated to launch in the mid-2030s.

TOP IMAGE: On May 20, the full-scale Engineering Development Unit Telescope for the LISA (Laser Interferometer Space Antenna) mission, still in its shipping frame, was moved within a clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Credit NASA/Dennis Henry

LOWER IMAGE: The prototype LISA telescope undergoes post-delivery inspection in a darkened NASA Goddard clean room on May 20. The entire telescope is made from an amber-colored glass-ceramic that resists changes in shape over a wide temperature range, and the mirror’s surface is coated in gold. Credit NASA/Dennis Henry

[penguinsdemise]

In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) observed the gravitational waves from two black holes spiralling into each other and merging for the first time. In the moments before they merged, the black holes were emitting more energy than all the stars in the universe, combined. The effect these gravitational waves had on the detector amounted to a change in length a fraction of a fraction the size of a atom.

Even the most cataclysmic events imaginable, that the entire universe pale besides, are cosmically insignificant.

being cosmically "insignificant" doesnt even matter like its not important......... like literally lets enjoy a strawberry