This illustration shows the NANOGrav project observing cosmic objects called pulsars in an effort detect gravitational waves – ripples in the fabric of space. The project is seeking a low-level gravitational wave background signal that is thought to be present throughout the universe. Credit: NANOGrav/T. Klein
An international team of scientists may be close to detecting faint ripples in space-time that fill the universe.
Pairs of black holes billions of times more massive than the Sun may be circling one another, generating ripples in space itself. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has spent more than a decade using ground-based radio telescopes to look for evidence of these space-time ripples created by behemoth black holes. This week, the project announced the detection of a signal that may be attributable to gravitational waves, though members aren’t quite ready to claim success.
Gravitational waves were first theorized by Albert Einstein in 1916, but they weren’t directly detected until nearly a century later. Einstein showed that rather than being a rigid backdrop for the universe, space is a flexible fabric that is warped and curved by massive objects and inextricably linked with time. In 2015, a collaboration between the U.S.-based Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer in Europe announced the first direct detection of gravitational waves: They were emanating from two black holes — each with a mass about 30 times greater than the Sun — circling one another and merging.
In a new paper published in the January 2021 issue of the Astrophysical Journal Supplements, the NANOGrav project reports the detection of unexplained fluctuations, consistent with the effects of gravitational waves, in the timing of 47 pulsars spread across the sky and measured over a span of 12 1/2 years.
Pulsars are dense nuggets of material left over after a star explodes as a supernova. As seen from Earth, pulsars appear to blink on and off. In reality, the light comes from two steady beams emanating from opposite sides of the pulsar as it spins, like a lighthouse. If gravitational waves pass between a pulsar and Earth, the subtle stretching and squeezing of space-time would appear to introduce a small deviation in the pulsar’s otherwise regular timing. But this effect is subtle, and more than a dozen other factors are known to influence pulsar timing as well. A major part of the work done by NANOGrav is to subtract those factors from the timing data for each pulsar before looking for signs of gravitational waves.
LIGO and Virgo detect gravitational waves from individual pairs of black holes (or other dense objects called neutron stars). By contrast, NANOGrav is looking for a persistent gravitational wave “background,” or the noiselike combination of waves created over billions of years by countless pairs of supermassive black holes orbiting one another across the universe. These objects produce gravitational waves with much longer wave lengths than those detected by LIGO and Virgo – so long that it might take years for a single wave to pass by a stationary detector. So while LIGO and Virgo can detect thousands of waves per second, NANOGrav’s quest requires years of data.
As tantalizing as the latest finding is, the NANOGrav team isn’t ready to claim they’ve found evidence of a gravitational wave background. Why the hesitation? In order to confirm direct detection of a signature from gravitational waves, NANOGrav’s researchers will have to find a distinctive pattern in the signals between individual pulsars. According to Einstein’s theory of general relativity, the effect of the gravitational wave background should influence the timing of the pulsars slightly differently based on their positions relative to one another.
At this point, the signal is too weak for such a pattern to be distinguishable. Boosting the signal will require NANOGrav to expand its dataset to include more pulsars studied for even longer lengths of time, which will increase the array’s sensitivity. NANOGrav is also pooling its data with those from other pulsar timing array experiments in a joint effort by the International Pulsar Timing Array, a collaboration of researchers using the world’s largest radio telescopes.
“Trying to detect gravitational waves with a pulsar timing array requires patience,” said Scott Ransom with the National Radio Astronomy Observatory and the current chairperson of NANOGrav. “We’re currently analyzing over a dozen years of data, but a definitive detection will likely take a couple more. It’s great that these new results are exactly what we would expect to see as we creep closer to a detection.”
Reference: “The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars” by Md F. Alam , Zaven Arzoumanian, Paul T. Baker, Harsha Blumer, Keith E. Bohler, Adam Brazier, Paul R. Brook, Sarah Burke-Spolaor, Keeisi Caballero, Richard S. Camuccio, Rachel L. Chamberlain, Shami Chatterjee, James M. Cordes, Neil J. Cornish, Fronefield Crawford, H. Thankful Cromartie, Megan E. DeCesar, Paul B. Demorest, Timothy Dolch, Justin A. Ellis, Robert D. Ferdman, Elizabeth C. Ferrara, William Fiore, Emmanuel Fonseca, Yhamil Garcia, Nathan Garver-Daniels, Peter A. Gentile, Deborah C. Good, Jordan A. Gusdorff, Daniel Halmrast, Jeffrey S. Hazboun, Kristina Islo, Ross J. Jennings, Cody Jessup, Megan L. Jones, Andrew R. Kaiser, David L. Kaplan, Luke Zoltan Kelley, Joey Shapiro Key, Michael T. Lam, T. Joseph W. Lazio, Duncan R. Lorimer, Jing Luo, Ryan S. Lynch, Dustin R. Madison, Kaleb Maraccini, Maura A. McLaughlin, Chiara M. F. Mingarelli, Cherry Ng, Benjamin M. X. Nguyen, David J. Nice, Timothy T. Pennucci, Nihan S. Pol, Joshua Ramette, Scott M. Ransom, Paul S. Ray, Brent J. Shapiro-Albert, Xavier Siemens, Joseph Simon, Renée Spiewak, Ingrid H. Stairs, Daniel R. Stinebring, Kevin Stovall, Joseph K. Swiggum, Stephen R. Taylor, Michael Tripepi, Michele Vallisneri, Sarah J. Vigeland, Caitlin A. Witt and Weiwei Zhu (The NANOGrav Collaboration), 21 December 2020, Astrophysical Journal Supplement Series. DOI: 10.3847/1538-4365/abc6a0
The NANOGrav team discussed their findings at a press conference on January 11, 2021, at the 237th meeting of the American Astronomical Society, held virtually from Jan. 10 to 15. Michele Vallisneri and Joseph Lazio, both astrophysicists at NASA’s Jet Propulsion Laboratory in Southern California, and Zaven Arzoumanian at NASA’s Goddard Space Flight Center in Maryland are co-authors of the paper. Joseph Simon, a researcher at University of Colorado Boulder and the paper’s lead author, conducted much of the analysis for the paper as a postdoctoral researcher at JPL. Multiple NASA postdoctoral fellows have participated in the NANOGrav research while at JPL. NANOGrav is a collaboration of U.S. and Canadian astrophysicists. The data in the new study was collected using the Green Bank antenna in West Virginia and the Arecibo dish in Puerto Rico before its recent collapse.
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.
