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Using a detector the size of a galaxy, astronomers detect gravitational waves from supermassive black hole pairs

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Credit: OzGrav / Swinburne / Carl Knox

When black holes and other enormously massive, dense objects whirl around one another, they send out ripples in space and time called gravitational waves. These waves are one of the few ways we have to study the enigmatic cosmic giants that create them.

Astronomers have observed the high-frequency “chirps” of colliding black holes, but the ultra-low-frequency rumble of supermassive black holes orbiting one another has proven harder to detect. For decades, we have been observing pulsars, a type of star that pulses like a lighthouse, in search of the faint rippling of these waves.

Today, research collaborations around the world—including ours, the Parkes Pulsar Timing Array—announced their strongest evidence yet for the existence of these waves.

What are gravitational waves?

In 1915, German-born physicist Albert Einstein presented a breakthrough insight into the nature of gravity: the .

The theory describes the universe as a four-dimensional “fabric” called spacetime that can stretch, squeeze, bend and twist. Massive objects distort this fabric to give rise to gravity.

A curious consequence of the theory is that the motion of massive objects should produce ripples in this fabric, called gravitational waves, which spread at the speed of light.

It takes an enormous amount of energy to create the tiniest of these ripples. For this reason, Einstein was convinced gravitational waves would never be directly observed.

A century later, researchers from the LIGO and Virgo collaborations witnessed the collision of two black holes, which sent a burst of gravitational waves chirping throughout the universe.

Now, seven years after this discovery, radio astronomers from Australia, China, Europe, India, and North America have found evidence for ultra-low-frequency gravitational waves.

A slow rumbling of gravitational waves

Unlike the sudden burst of gravitational waves reported in 2016, these ultra-low-frequency gravitational waves take years or even decades to oscillate.

They are expected to be produced by pairs of supermassive black holes, orbiting at the cores of distant galaxies throughout the universe. To find these gravitational waves, scientists would need to construct a detector the size of a galaxy.

Or we can use pulsars, which are already spread across the galaxy, and whose pulses arrive at our telescopes with the regularity of precise clocks.

CSIRO’s Parkes radio telescope, Murriyang, has been observing an array of these pulsars for almost two decades. Our Parkes Pulsar Timing Array team is one of several collaborations around the world that have today announced hints of gravitational waves in their latest data sets.

Other collaborations in China (CPTA), Europe and India (EPTA and InPTA), and North America (NANOGrav) see similar signals.

Using a detector the size of a galaxy, astronomers find strongest evidence yet for gravitational waves from supermassive black h
As gravitational waves warp spacetime around Earth, they distort the arrival times of radio waves from distant pulsars. Credit: OzGrav / Swinburne / Carl Knox

The signal we are searching for is a random “ocean” of gravitational waves produced by all the pairs of supermassive black holes in the universe.

Observing these waves is not only another triumph of Einstein’s theory, but has important consequences for our understanding of the history of galaxies in the universe. Supermassive are the engines at the heart of galaxies that feed on gas and regulate star formation.

The signal appears as a low-frequency rumble, common to all pulsars in the array. As the gravitational waves wash over Earth, they affect the apparent rotation rates of the pulsars.

The stretching and squeezing of our galaxy by these waves ultimately changes the distances to the pulsars by just tens of meters. That’s not much when the pulsars are typically about 1,000 light-years away (that’s about 10,000,000,000,000,000,000 meters).

Remarkably, we can observe these shifts in spacetime as nanosecond delays to the pulses, which radio astronomers can track with relative ease because pulsars are such stable natural clocks.

What has been announced?

Because the ultra-low-frequency gravitational waves take years to oscillate, the signal is expected to emerge slowly.

First, radio astronomers observed a common rumble in the pulsars, but its origin was unknown.

Now, the unique fingerprint of gravitational waves is beginning to appear as an attribute of this signal, observed by each of the pulsar timing array collaborations around the world.

This fingerprint describes a particular relationship between the similarity of pulse delays and the separation angle between pulsar pairs on the sky.

The relationship arises because spacetime at Earth is stretched, changing the distances to pulsars in a way that depends on their direction. Pulsars close together in the sky show a more similar signal than pulsars separated at right angles, for example.

The breakthrough has been enabled by improved technology at our observatories. The Parkes Pulsar Timing Array has the longest high-quality data set, thanks to the advanced receiver and signal processing technology installed on Murriyang. This technology has enabled the telescope to discover many of the best pulsars used by collaborations around the globe for the gravitational wave searches.

Earlier results from our collaboration and others showed the signal expected from gravitational waves was missing from pulsar observations.

Now, we seem to be seeing the signal with relative clarity. By segmenting our long data set into shorter “time-slices,” we show the signal appears to be growing with time. The underlying cause of this observation is unknown, but it may be that the gravitational waves are behaving unexpectedly.

The new evidence for ultra-low-frequency gravitational waves is exciting for astronomers. To confirm these signatures, the global collaborations will need to combine their , which increases their sensitivity to many-fold.

Efforts to produce this combined data set are now in progress under the International Pulsar Timing Array project, whose members met in Port Douglas in Far North Queensland last week. Future observatories, like the Square Kilometre Array under construction in Australia and South Africa, will turn these studies into a rich source of knowledge about the history of our universe.

 

This article is republished from The Conversation under a Creative Commons license. Read the original article.The Conversation

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Using a detector the size of a galaxy, astronomers detect gravitational waves from supermassive black hole pairs (2023, July 1)
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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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