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Regulars at this site will surely know of Robert Lang, physicist and origami master (art website here) whom I met a while back at the Kent Presents meetings. We became friendly and thereafter he contributed both wildlife photos and origami photos to this website (see all his posts here).

I was scheduled to meet Robert and his wife Diane today after the meetings and get a tour of their home and studio (she’s an author), thereafter then sallying forth to dinner. I hadn’t seen Robert in years, and had never met Diane, so I was looking forward to visiting their digs and to seeing some of the famous origami.

The problem was that their home and studio were in Altadena, California, near Los Angeles, so you can guess what I’m going to say next.

The home and studio are no more, taken down by wildfire. But I’ll let Robert tell the tale. His words, printed with permission, are indented below, and are supplemented with narrated videos (there are even subtitles).  This is the story of a family who lived through the fire but lost everything—except for the most important things: their lives and their animals.

Note that they actually lost two houses, as they had just bought another down the street.

Late Tuesday afternoon, we heard about the Eaton Fire, which started over in Eaton Canyon, about 2 miles to our east and several ridges over. The initial reports were that the wind was driving the fire to the east (away from us), so we were hopeful. At about 6:30 pm, though, my neighbor texted the neighborhood group that he saw a glow over the ridge to our east, and I headed up to my studio to see. By 7:30 pm I saw the fire crest that ridge and we received the “evacuate NOW” notice, so I threw as much as I could grab into my car and headed down, while my wife did the same from our home (with the dogs, tortoises, snake, and tarantula that live with us).

We spent the next few hours driving and parking to try to watch things from a distance. Surprisingly, the evacuation zone ended just to the west of our neighborhood, so after a while, I started making my way to the edge of the zone, staying out of the way of the many emergency vehicles, and presently found a spot from which I could walk to the edge of the canyon that separated me from my studio. From there, I could see the studio; I could also see that the entire multi-thousand-foot mountainside above it was in sheets of flame. The wind was blasting through the canyons, driving 50-foot plumes of flame and embers horizontally. About 1:30 am, I saw a flare-up right at the studio, and within about 10 minutes, it was engulfed. I also realized about that time that the fire would likely take down the telephone poles (and thus, potentially live wires) along my route, so I beat a hasty retreat to my car, and before long, the authorities announced that our area was now evacuation zone. We drove down the hill to Pasadena, found a quiet neighborhood out of the smoke (and, we hoped, the path of the fire), and spent a fitful rest of the night in our cars, awaiting what the morning would bring.

In the morning, my wife stayed with the animals and I drove up the hill to see what became of our house. Major roads were blocked off, but I wove through the neighborhoods, dodging still-burning homes (though the worst was past), downed wires, downed trees, and random debris, until I could get up to my neighborhood. It was a zone of total devastation: nearly all homes burned–and definitely mine. (Actually, both of ours; we had just moved down the street, so both our old house–just moved out of–and the new house–just moved into–were leveled.) I made my way up to my studio at the top of the hill, passing street after street of nothing but smoldering ruins. When I made it up, I found something incredible: the row of houses below my studio had entirely survived! I texted their owners the good news. I could see, though, that my studio had not; I parked (debris blocked my driveway), walked up, and surveyed the destruction, took a few videos and pictures for records, then high-tailed it down the hill.

Right now, the estimates are that 7000 structures were damaged or destroyed. It looks like about 2/3 of Altadena is gone. There’s a lot of snark on the internets about the rich people/celebrities/influencers in Pacific Palisades losing their houses. I haven’t seen similar snark about Altadena, which is a mixed-class, mixed-race community. There are turn-of-the-century buildings, craftsman houses, bungalows, tiny starter homes, and yes, a few mansions left over from the days when it was the summer playground of the rich. My wife grew up here; her father built their house himself in the 40s after clearing the orange groves from the parcel he bought. On the main drag downtown, the local hardware store was where you ran into your neighbors; Fox’s Restaurant had been a local landmark since 1955. All that is gone.

Ironically, I had recently returned from a business trip to Dresden, Germany, which was (famously) fire-bombed and leveled in WWII. They rebuilt. So will we. But it will be a long road to recovery.

*****************

Here a Cal Fire map of fire damage. The damaged area covers about 2/3 of Altadena. My home and studio is in the top middle of the burned civilized area, just to the left of the vertical black bar on the map.

This map is an understatement; I know some of the areas shown in gray actually burned.

Here are a few of the videos Robert posted on his YouTube site:

Panorama of the fire from the studio:

View of the mountains from the house:

Views of the destroyed house:

Views of the destroyed studio:

From Robert:

Here’s one more image for you: house-by-house fire damage. I’ve annotated where my places were. Not much left of the neighborhood.

[The key to above]: red=burned, black = OK, amber=damaged, green=“affected” (whatever that means).

Distance-wise, the studio and the houses are about a half mile apart by road, less by walking (there’s a trail up the canyon). An easy walk, except for the elevation gain (studio is about 200’ higher in elevation), so I usually drove.

Click to enlarge:  Arrows: studio is at the top, the old house at lower center, and the new house at lower right.  I’m struck by the patchy locations of the houses that survived.

As you can tell from the narration, Robert appears remarkably calm about this, as he was in his email to me about the destruction, which was headed “change of plans.”  I would be wailing with grief! But Robert and I do have one thing in common: a compulsion to document. His is with words and videos, mine involves in putting them on this site.

Best of luck, Robert and Diane, and of course we’re all sorry for your loss.

A range of brainwave-reading devices and other gadgets aim to monitor our nervous systems and intervene to improve our well-being. Do they work?

Two companies, Firefly Aerospace and ispace, are aiming to make the second and third successful private landings on the moon - and both are launching on the same Falcon 9 rocket

A marine crustacean that looks like Darth Vader’s helmet has been recognised as a new species, but it could be under threat from trawling due to its popularity in Vietnamese restaurants

Meanwhile, in Dobrzyn, Hili is the boss cat, of course:

A: Hili, you are not helping me when you lie here.
Hili: I’m supervising. Find somebody else to help you.

Ja: Hili, nie pomagasz mi jak tu leżysz.
Hili: Ja nadzoruję, do pomagania znajdź sobie innych.

Cloud seeding would seem like an easy and obvious way to create rain where none existed before. Is it really that simple?

The problem with debating a flat-Earther is that they didn’t arrive at their conclusions from the weight evidence, so using the evidence isn’t going to work to change their minds.

That said, the evidence for the curved Earth is abundant. Besides the enormous body of photographic documentation, it’s even possible to do the experiment yourself. For example, I recently flew from New York City to Doha, from there to Singapore, then to Brisbane, then to Dallas, then back home. I followed an eastward course for my entire journey, and ended up back where I started. That’s only possible on a globe.

On that journey I got to enjoy plenty of views of the night sky, and one of the most striking features was that the sky was different. On a flat Earth, everyone would get the same view of the sky, but there were stars that I could only see at home and couldn’t on my trip, and vice versa.

And lastly, during a lunar eclipse the shadow of the Earth passes over the Moon. That shadow is always a circle, and only spheres are capable of casting circular shadows 100% of the time, regardless of angle.

But like I said, it’s not about the evidence. People who believe that the Earth is flat think that we are being lied to by scientists and political leaders. Many people don’t trust their society, and especially leaders of that society. And most especially elite leaders of that society. Scientists are indeed elite leaders of the government, academia, and other powerful institutions. By claiming that the Earth is flat, people are really expressing a deep distrust of scientists and science itself.

Distrust in science is a deep, thorny issue. But one way to rebuild trust is to simply listen. I know it sounds counter-intuitive, but studies have shown that people tend to trust other people, not necessarily the facts. So if you encounter a flat-Earth, as I have many times, don’t bother getting in a debate. Instead, change the subject so that you focus on something you find wonderful or extraordinary about the universe or about science. Maybe it’s an exciting new observation, or a clever experimental result, or an example of a real-world impact from scientific learning.

By building bridges based on shared wonder, awe, and curiosity, we can defuse the tension, moving around the flashpoint caused by a triggering proclamation and instead focusing on common ground. That’s the only place where trust can take root. And once trust is established, the question of the geometry of the Earth simply fades into the background.

The post How to Debate a Flat-Earther appeared first on Universe Today.

Researchers have developed a drastically smaller and more energy efficient method of creating coveted photon pairs that influence each other from any distance. The technology could transform computing, telecommunications, and sensing.

Researchers have developed a drastically smaller and more energy efficient method of creating coveted photon pairs that influence each other from any distance. The technology could transform computing, telecommunications, and sensing.

Although extremely flammable, cotton is one of the most commonly used textiles due to its comfort and breathable nature. However, in a single step, researchers can reduce the flammability of cotton using a polyelectrolyte complex coating.

The traditional theory of black hole formation seems to struggle to explain how black holes can merge into larger more massive black holes yet they have been seen with LIGO. It’s possible that they may have formed at the beginning of time and if so, then they may be a worthy candidate to explain dark matter but only if there are enough of them. A team of researchers recently searched for microlensing events from black holes in the Large Magellanic Cloud but didn’t find enough to account for more than a fraction of dark matter. 

Classical black hole formation theory explains how they from the remnants of massive stars that have reached the end of their life and exhausted their fuel. When a star with a mass greater than about 20 times that of the Sun reaches the end of its life, it undergoes a supernova explosion, ejecting most of its outer layers into space. 

3D rendering of a rapidly spinning black hole’s accretion disk and a resulting black hole-powered jet. Credit: Ore Gottlieb et al. (2024)

The core that is left behind is no longer supported by the pressure from nuclear fusion so it collapses under its own gravity. If the core’s mass is sufficient, typically several times the mass of the Sun, it will continue to collapse into a singularity—an infinitely dense point with an extremely strong gravitational pull. This process creates a black hole, characterised by the event horizon, a boundary beyond which nothing, not even light, can escape its gravity.

That’s a widely accepted description of the formation of black holes. However a recent set of observations using gravity wave detectors has identified some massive black holes. When compared to those that can be seen in the Milky Way they bare little resemblance. One possible explanation suggests that they may have instead formed from fluctuations in density during an earlier part of the universe’s history. These are known as primordial black holes and some theories suggest that they may account for dark matter. Possibly even up to 100% of the dark matter to account for the observed black hole merger rates. If they exist in the dark matter halo of the Milky Way then they should be observable by gravitational microlensing events. 

Image from NASA’s Hubble Space Telescope of a galaxy cluster that could contain dark matter (blue-shaded region). (Credit: NASA, ESA, M. J. Jee and H. Ford et al. (Johns Hopkins Univ.))

Previous studies have failed to identify such events but the team believe the observations were not sensitive enough. The paper published by Przemek Mroz from the University of Warsaw and team offer their findings of long-timescale microlensing events (events that occur over extended periods of times from weeks sometimes even years) in the Large Magellanic Cloud over the 20 years of the OGLE (Optical Gravitational Lensing Experiment) survey. The survey began in 1992 and is a long term study to detect microlensing events and observe variable phenomenon such as variable stars and supernova. It’s based at the Las Campanas Observatory in Chile and using the 1.3 metre telescope to monitor sections of sky. 

The Large Magellanic cloud. Credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State University) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.

Having analysed the 20 years of data they found no events within the timescales longer than a year. Other shorter period events were identified but these are more likely down to stellar events than supermassive primordial black holes (PMB.) They find therefore, that PMB’s up to 6.3 million solar masses cannot make up more than 1% of dark matter. Those in the larger category up to 860 million solar masses cannot compose any more than 10% of dark matter. The unmistakable conclusion is that PMBs, based on the observations in the Large Magellanic Cloud, cannot account for a significant fraction of dark matter.

Source : No massive black holes in the Milky Way halo

The post LIGO Has Detected Unusual Black Holes Merging, But they Probably Don’t Explain Dark Matter appeared first on Universe Today.

Fast Radio Bursts (FRBs) are mysterious pulses of energy that can last from a fraction of a millisecond to about three seconds. Most of them come from outside the galaxy, although one has been detected coming from a source inside the Milky Way. Some of them also repeat, which only adds to their mystery.

Though astrophysicists think that a high-energy astrophysical process is the likely source of FRBs, they aren’t certain how they’re generated. Researchers used gravitational waves (GWs) to observe one nearby, known source of FRBs to try to understand them better.

The only confirmed FRB source in the Milky Way is a neutron star with a powerful magnetic field—a magnetar—named SGR 1935+2154. Its FRB was detected in 2020 and was the first one to be connected to a source. Though SGR 1935+2154 is around 20,000 light-years away, it’s still close enough to be studied.

In new research in The Astrophysical Journal, scientists used the British-German GEO600 gravitational wave detector to probe any connections between the FRBs and gravitational waves. The research is “A Search Using GEO600 for Gravitational Waves Coincident with Fast Radio Bursts from SGR 1935+2154,” and the lead author is A. G. Abac. Abac is from the Max Planck Institute for Gravitational Physics.

FRBs are extraordinarily energetic, and so are magnetars. Connecting an FRB with the magnetar SGR 1935-2154 is a big step in understanding FRBs, although there are still a whole host of unanswered questions. Some magnetars repeatedly emit FRBs and also glow in X-rays. Magnetars can experience powerful star quakes when tension in their crusts is released, and the released energy shakes the magnetar’s magnetic field, releasing the FRBs and X-rays. Researchers have wondered if those same quakes might generate gravitational waves.

Artist’s conception of a starquake cracking the surface of a neutron star. Credit: Darlene McElroy of LANL

Can observing the magnetar for GWs open a window into magnetars and the processes that generate FRBs?

“Observing fast radio bursts and gravitational waves from a magnetar at almost simultaneously would be the evidence we have been looking for for a long time,” said James Lough, lead scientist of the German-British gravitational-wave detector GEO600 at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hanover. A simultaneous observation of FRBs and GWs could confirm the common origin in the stellar quakes generated by the neutron star. “That’s why we worked with an international team to analyze data we took with GEO600 while a magnetar on our cosmic doorstep was emitting fast radio bursts,” adds Lough.

If the magnetar is generating GWs, they’ll be strong when they reach our detectors, and their effects should be easier to observe. Between April 2020 and October 2022, SGR 1935+2154 generated three episodes of FRBs, and GEO600 was listening. The GW detector is part of the global network of GW detectors.

The GEO600 GW detector is near Hanover, Germany. While other GW detectors suffered shutdowns during the COVID-19 pandemic, GEO600 continued to operate. LIGO, for example, resumed operations post-pandemic, including some new upgrades. Image Credit: Max Planck Institute for Gravitational Physics (Albert Einstein Institute)/Milde Marketing

“It was essential that GEO600 could continue observing while all the other detectors were in an upgrade phase,” explained Lough. “Otherwise, we would have missed the opportunity of having gravitational-wave data during these fascinating events occurring so close to us.”

Unfortunately, careful analysis of GEO600’s data showed no evidence of GWs. However, the detector’s observations were still valuable. Since the magnetar is so close to us, even the lack of detection provided some new information.

This isn’t the first time that scientists have used GW detectors to search for GWs emitted simultaneously with FRBs, as well as for GWs from magnetar bursts and pulsar glitches. Different researchers have used the more powerful LIGO, Virgo, and KAGRA (LVK) collaborations to find them without success. “While no detections were found in these studies, the searches have established upper limits on GW energy that may have been emitted in association with these events,” the authors write in their research.

This illustration shows the merger of two supermassive black holes and the gravitational waves that ripple outward as the black holes spiral toward each other. Image Credit: LIGO/T. Pyle

The LVK detectors are larger and more powerful than GEO600. Their data shows that the maximum possible gravitational-wave energy that could have been emitted during the magnetar’s 2020 to 2022 FRBs without being detected must have been up to 10,000 times smaller than astronomers had concluded from previous studies.

Different models explain how GWs are produced in FRBs, and the GW observations aren’t yet sensitive enough to distinguish between them. However, by establishing limits for the strength of the GWs, the GW observations are still providing information that is helping scientists refine their models.

The attempt to link GWs and FRBs is really only beginning. While LIGO/Virgo weren’t able to observe the magnetar during its last FRBs, they will hopefully be operational during the next episode. This time, their effectiveness and sensitivity will have been upgraded.

For a long time, astrophysicists have theorized that magnetars are the source of FRBs, and the detection of FRBs from SGR 1935+2154 confirms this, at least for some FRBs. However, the exact mechanism behind their generation remains elusive. “The relationship between these magnetar bursts and FRBs is poorly understood, but are likely to be caused by different physical processes, even if the underlying magnetar behaviour may be related,” the authors write in their conclusion.

If future GW observations of the magnetar with the upgraded LIGO/Virgo and KAGRA observatories can show that GWs are emitted simultaneously with FRBs, that will be a huge development. “Given the increased sensitivity of these detectors compared to GEO600, any SGR 1935+2154 FRB during the remainder of O4 (Observing Run 4) could provide another opportunity to probe the GW-FRB connection,” the authors of the study explain.

“Things could get exciting really soon. We hope that the magnetar, which has been quiet for two years and has not emitted any radio bursts, will become active again in the next few months,” says Karsten Danzmann, director at the AEI and director of the Institute for Gravitational Physics at Leibniz University Hannover. The international detector network is partway through an observing run that will continue until June 2025. “With the data from the more sensitive instruments, we will be able to look even more closely whether the fast radio burst of magnetars are accompanied by gravitational waves and thus perhaps solve a very old mystery,” says Danzmann.

The post Gravitational Waves Could Give Us Insights into Fast Radio Bursts appeared first on Universe Today.

Last year, Meta allowed thousands of paid ads containing sexually explicit imagery on social media platforms, including Facebook and Instagram

Volcanoes have been proposed as the reason for the extinction of the Neanderthals and the hobbits of Indonesia, but the end of those species may not have come from a single, dramatic event

Bats depend on open bodies of water such as small ponds and lakes for foraging and drinking. Access to water is particularly important for survival in the increasingly hot and dry summers caused by climate change, the time when female bats are pregnant and rear their young. A scientific team has now shown that access to drinking sites is hampered by wind turbines in agricultural landscapes: Many bat species avoid the turbines and water bodies located close to the turbines for several kilometers.

The night sky has always played a crucial role in navigation, from early ocean crossings to modern GPS. Besides stars, the United States Navy uses quasars as beacons. Quasars are distant galaxies with supermassive black holes, surrounded by brilliantly hot disks of swirling gas that can blast off jets of material. Following up on the groundbreaking 2020 discovery of newborn jets in a number of quasars, aspiring naval officer Olivia Achenbach of the United States Naval Academy has used NASA's Hubble Space Telescope to reveal surprising properties of one of them, quasar J0742+2704.

The name 'blue lurker' might sound like a villainous character from a superhero movie. But it is a rare class of star that NASA's Hubble Space Telescope explored by looking deeply into the open star cluster M67, roughly 2,800 light-years away.

The Sun can kill. Until Earth developed its ozone layer hundreds of millions of years ago, life couldn’t venture out onto dry land for fear of exposure to the Sun’s deadly ultraviolet radiation. Even now, the 1% of its UV radiation that reaches the surface can cause cancer and even death.

Astronauts outside of Earth’s protective ozone layer and magnetic shield are exposed to far more radiation than on the planet’s surface. Exposure to radiation from the Sun and elsewhere in the cosmos is one of the main hurdles that must be cleared in long-duration space travel or missions to the lunar and Martian surfaces.

Unfortunately, there’s no harmonized approach to understanding the complexity of the hazard and protecting astronauts from it.

Astronauts haven’t gone further into space than the ISS for decades. But if Artemis lives up to its promise, they’re about to leave Earth and its protective environment behind. Artemis will land astronauts on the Moon, which could be an intermediate step to an eventual landing on Mars. What hazards does radiation pose, and how can astronauts be protected?

A new research editorial in the Journal of Medical Physics examines the issue. It is titled “System of radiological protection: Towards a consistent framework on Earth and in space.” The lead author is Werner Rühm from the Federal Office for Radiation Protection, München (Neuherberg), Germany. The same issue of the Journal of Medical Physics contains several other articles about radiation exposure. Together, they’re part of a research effort by the International Commission on Radiological Protection (ICRP) to update and harmonize radiation exposure guidelines.

The term ‘radiation’ is descriptive enough that most of us recognize the potential threat. However, when it comes to variable space environments and human physiology, the word holds a lot more detail. The authors use the term ‘mixed radiation field’ to describe the radiation environment astronauts must endure.

“The mixed-radiation field outside and within a space vehicle is of particular complexity involving not only low-linear energy transfer (LET) radiation such as gamma radiation, electrons, and positrons but also high-LET radiation such as neutrons and heavy ions,” the authors write. The components of the field contain a wide span of particles with different energy levels. “The quantitative and even qualitative risks of exposure to the combined impact of a complex radiation environment, microgravity, and other stressors remain unclear,” they explain.

One problem in preparing for exposure to these mixed radiation fields is the different approaches taken by different countries and space agencies.

NASA astronauts exploring Mars on future missions, perhaps starting in the 2030s, will require protection from long-term exposure to the cancer-causing space radiation environment. Credit: NASA.

According to lead author Rühm, this disharmony is caused by “the complex and dynamic radiation environments and an incomplete understanding of their biological consequences. Because of this, space agencies follow somewhat different concepts to quantify radiation doses and their resulting health effects.”

This paper and its companions are part of an effort to unify our understanding of radiation and its hazards and to harmonize the various approaches to dealing with them. The goal is to develop a “consistent radiological protection framework.” To do that, the authors explain that several questions need answers:

• Which radiation-induced health effects should be considered?
• What dose quantities are the best for the radiological protection of astronauts?
• Which metrics should be used to quantify radiation-related health risks?
• How do we address sex and age differences in radiation risk?
• What kind of protection criteria should be applied?
• How do we decide on the tolerability of radiation-induced risks, given that astronauts are exposed to many other occupation-related risks?
• How do we deal with the fact that increased health risks due to radiation exposure may persist after an astronaut’s career ends?
• How do we communicate radiation risk and make a comparison with other health hazards in a meaningful way?
• How do we harmonize national radiological protection guidelines, given that different subpopulations might have different levels of risk tolerance?

This list of questions vividly illustrates the complexity of the radiation exposure problem. Answering them will help harmonize the approach to radiation on space missions.

Rühm and his colleagues want to support space agencies as they harmonize and coordinate their guidelines for astronauts’ exposure to radiation. The goal is to develop an approach consistent with the thorough guidelines followed here on Earth.

The difference between how males and females respond to radiation illustrates one of the problems in developing radiation exposure guidelines. In past decades, much medical research was based on males and the results were applied to females as well. According to Rühm, the same thing has happened with radiation.

“It is worth mentioning that on Earth, the System developed by ICRP does not include any systematic differentiation between recommendations on limits for males and females,” the authors write. This is in spite of the fact that it is “well known that there are individual differences in radiation sensitivity between males and females.” The difference is largely because reproductive tissue is more susceptible to radiation than other tissue, and women have more of it.

This infographic shows how men’s and women’s bodies react differently to spaceflight. It’s also becoming well-known that women are more sensitive to radiation exposure. Image Credit: NASA/NSBRI

NASA has developed a different approach to radiation exposure because of this. “This standard is based on a REID (Risk of Exposure-Induced Death) of 3% calculated for cancer mortality in the most vulnerable group of astronauts––35-year-old females,” the authors write. Scientists understand that females are more vulnerable to radiation than males and that younger females are more sensitive than older females. It’s worth noting that astronauts are unlikely to be under the age of 35.

The difference between the sexes isn’t the only thing that needs to be addressed when it comes to astronauts’ exposure to radiation. Different sub-populations might have different risk factors; there are lifestyle-related risks, different mission architectures hold different risks, and many other factors come into play. Harmonizing an approach with all of these different factors is a daunting task.

Difficult or not—and there’s nothing easy about space travel—a harmonized and coordinated approach to understanding the radiation risk is the logical next step. Artemis itself is a collaboration between different nations and agencies, and it’s only fair to the astronauts themselves that they have the same protections and considerations when it comes to radiation exposure.

Rühm and his colleagues hope that their work will help lead to a harmonized approach to assessing the radiation hazards faced by astronauts in mixed radiation fields. We owe it to the people willing to put their lives on the line and serve as astronauts.

“Adventurous people have always tried to widen their horizon, this is part of our very nature as humans,” Rühm says. “Our work contributes to and supports one of the most exciting and challenging human endeavors ever undertaken.”

The post As We Explore the Solar System, Radiation Will Be One of Our Greatest Threats appeared first on Universe Today.

The tattoos of 1200-year-old mummies from Peru can now be seen in exquisite detail, showing fine markings that may have been made with cactus needles or animal bones

In February 2016, scientists working for the Laser Interferometer Gravitational-Wave Observatory (LIGO) made history by announcing the first-ever detection of gravitational waves (GW). These waves, predicted by Einstein’s Theory of General Relativity, are created when massive objects collide (neutron stars or black holes), causing ripples in spacetime that can be detected millions or billions of light years away. Since their discovery, astrophysicists have been finding applications for GW astronomy, which include probing the interiors of neutron stars.

For instance, scientists believe that probing the continuous gravitational wave (CW) emissions from neutron stars will reveal data on their internal structure and equation of state and can provide tests of General Relativity. In a recent study, members of the LIGO-Virgo-KAGRA (LVK) Collaboration conducted a search for CWs from 45 known pulsars. While their results showed no signs of CWs emanating from their sample of pulsars, their work does establish upper and lower limits on the signal amplitude, potentially aiding future searches.

The LVK Collaboration is an international consortium of scientists from hundreds of universities and institutes worldwide. This collaboration combines data from the Laser Interferometer Gravitational-Wave Observatory’s (LIGO) twin observatories, the Virgo Observatory, and the Kamioka Gravitational Wave Detector (KAGRA). The preprint of the paper, “Search for continuous gravitational waves from known pulsars in the first part of the fourth LIGO-Virgo-KAGRA observing run,” recently appeared online.

First discovered in 1967, pulsars are a class of neutron stars that have strong magnetic fields, causing them to emit beams of electromagnetic radiation from their poles. They also rotate rapidly, creating a strobing effect reminiscent of a lighthouse. Given their stability and predictability, pulsars present an opportunity to search for continuous gravitational waves (CWs). Unlike transient GW, which are produced by binary black hole and neutron star mergers, CWs are long-lasting signals expected to come from massive, spinning objects (like pulsars).

To date, all GW events observed by astronomers have been transient in nature. To find evidence of these events, the team searched for signals from 45 known pulsars (and a narrowband search for 16 pulsars) from the first part of the fourth LIGO-Virgo-KAGRA observing run (O4a). They also employed three independent data analysis methods and two different emission models. As they indicated in their paper, no CW signals were detected, but the results were still informative:

“No evidence of a CW signal was found for any of the targets. The upper limit results show that 29 targets surpass the theoretical spin-down limit. For 11 of the 45 pulsars not analyzed in the last LVK targeted search, we have a notable improvement in detection sensitivity compared to previous searches. For these targets, we surpass or equal the theoretical spin-down limit for the single-harmonic emission model. We also have, on average, an improvement in the upper limits for the low-frequency component of the dual-harmonic search for all analyzed pulsars.”

The team also conducted a search for polarization that is consistent with a theory of gravitation alternative to General Relativity (Brans–Dicke theory). While CWs remain unconfirmed, the team predicts that a full analysis of the full O4 dataset will improve the sensitivity of targeted/narrowband searches for pulsars and CWs.

Further Reading: arXiv

The post LIGO Fails to Find Continuous Gravitational Waves From Pulsars appeared first on Universe Today.