An artist’s interpretation shows an array of pulsars being affected by gravitational ripples produced by a supermassive black hole binary in a distant galaxy.Handout
Somewhere, far away, the universe is humming, and for the first time, scientists are picking up the tune.
But that hum is not audible; rather, it consists of unimaginably long waves of gravitational energy that alternately stretch and squeeze space as they propagate in all directions. Their suspected source: hundreds of thousands of supermassive black holes swinging around each other like vigorous couples shaking the floor at a cosmic barn dance.
Such is the world of low frequency gravitational wave astronomy – a search for undulations so vast that, even thought they are coming at us at the speed of light, any single wave might take a decade or more to crest as it passes by Earth. The change is so subtle that scientists must employ special techniques just to demonstrate that the waves are there at all.
“These truly are among the lowest notes in the cosmic symphony. It’s an amazing feat to have found evidence for signals like this,” said Ingrid Stairs, an astronomer at the University of British Columbia and member of the NANOGrav collaboration, a North America-wide effort to search for the elusive low frequency waves.
The project’s latest measurements were published Thursday in the Astrophysical Journal Letters, in co-ordination with teams in Europe, India, Australia and China that have been independently looking for the same signal. All the findings are consistent with the existence of low frequency gravitational waves, though NANOGrav team members said the data are close but not yet at the 3.5 million-to-one-certainty level considered the gold standard for reporting new discoveries in physics.
“We’re not saying the word ‘detection,’ ” Dr. Stairs said.
If their interpretation is correct, researchers have used gravity to open up a new window into the unseen depths of the universe and shed light on the formation and evolution of the heaviest objects we know – or it could mean the discovery of something entirely new and unexpected.
Long predicted by Einstein’s theory of general relativity, gravitational waves are disturbances in space that are produced whenever massive objects move very quickly. Their existence was first confirmed in 2015 by the Laser Interferometer Gravitational-Wave Observatory. The U.S.-based facility uses laser light reflecting back and forth between mirrors that are four kilometres apart to pick up slight vibrations that occur when gravitational waves are traversing through the experiment.
Since acquiring the sensitivity to detect the waves, LIGO has recorded many signals that come from colliding black holes a few dozen times the sun’s mass. Those signals appear as short-lived chirps in the data that momentarily jiggle the detector before fading away.
This week, scientists are reporting something quite different: not high-pitched chirps but a deep and continuous drone that permeates all of space. Such a drone would be expected to arise not from one collision but from the collective motion of many of the largest black holes in the universe – each one carrying the mass of millions of suns. Black holes of such extreme mass are known to form at the centres of distant galaxies. And while they may form separately, two such black holes can find themselves bound together in a tight orbit after their host galaxies merge.
Neither LIGO nor any other detector on Earth is large enough to sense the gravitational waves emanating from such a massive duo. However, by checking Earth’s position relative to other objects in space, astronomers have shown that our planet is acting very much like a cork bobbing around in slow motion exactly as would be expected from the low frequency waves.
“This is really compelling evidence for a background of gravitational waves,” said Steve Taylor, an astronomer at Vanderbilt University in Tennessee and current chair of NANOGrav during a briefing on the find. The collaboration harnessed researchers and facilities across North America to search for the effect.
To conduct its search, the team used radio telescopes in multiple locations to carefully monitor pulsars – compact, rotating objects scattered around our Milky Way galaxy that are left behind when stars exhaust their fuel and explode as supernovas. Some pulsars can spin as much as 1000 times per second, which makes then ideal natural timers because their rotations are so precise and consistent. As Earth is buffeted by gravitational waves, the planet’s back and forth motion can be spotted by comparing pulsars in different directions and checking for slight discrepancies in timing. The hitch is that it takes years of measurements to see the gradual change caused by passing low frequency gravitational waves.
Achieving that result reliably “has taken a small army of people to do everything right,” Dr. Stairs said.
Other teams used the same pulsar-timing approach to arrive at comparable results. And while the existence of low frequency gravitational waves has long been suspected, the details include a few puzzles. For example, if the background hum is produced solely by close pairs of supermassive black holes circling each other, then the pairs are more common and somewhat more massive on average than standard theories predict.
This had some researchers this week pointing to even more exotic possibilities for explaining the cause of the gravitational waves, including cosmic strings: hypothetical defects in spacetime that some theories predict could have formed during the Big Bang.
Luis Lehner, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ont., who was not part of the collaboration, said that theorists may have difficulty explaining how pairs of supermassive can get close enough to each other often enough to match what observers are now finding in their data.
“They take too long to merge, but we’re not seeing that,” he said. “Somehow they get together … it’s nature reminding us that it’s always going to be smarter than we are.”
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
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.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
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