Black holes are sneaky. They lurk out there in the dark, not giving off any detectable radiation, making them very hard to find. But they have a weakness: they’re extremely messy eaters. And this propensity has allowed astronomers to zero in on something elusive: the “missing link” middleweight black hole.
A colossal X-ray flare observed in 2006 was suspected to be the spillage from an intermediate-mass black hole – 50,000 times the mass of the Sun – as it tore apart and devoured a star. By eliminating a major competing hypothesis, researchers are now confident they’re on the right track, and it’s a pretty big deal.
Black holes are mysterious at the best of times. Because they emit no light, we can’t see them, and we have to measure their properties based on the effect they have on the stuff around them – whether it’s orbiting objects, or stuff they’re actually accreting, a process that generates a great deal of heat and light.
But intermediate-mass black holes up the mystery ante. Because while we’ve found really titchy stellar-mass black holes (up to 100 times the mass of the Sun) and really chonky supermassive black holes (over 100,000 times the mass of the Sun, although they can get much bigger), the weight class in between has proven extremely elusive.
We’ve had hints that intermediate-mass black holes are out there, but nothing conclusive. This new paper, according to its authors, is the best evidence yet.
That evidence hinges on a huge X-ray flare called 3XMM J215022.4−055108 (or J2150−0551 for short). While the light show had been going for three years already, the flare was first detected in 2006 by two powerful X-ray space telescopes – NASA’s Chandra X-ray Observatory and the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton).
(NASA, ESA, and D. Lin (University of New Hampshire)
In 2018, physicist and astronomer Dacheng Lin of the University of New Hampshire and colleagues published a paper based on observations from these telescopes. The flare, they concluded, was likely the radiation blasted out as an intermediate-mass black hole devoured a star.
Now Lin and his team have obtained and analysed new multi-wavelength observations from XMM Newton and the Hubble Space Telescope. And they’re more certain than ever that this is what caused the flare.
“Intermediate-mass black holes are very elusive objects, and so it is critical to carefully consider and rule out alternative explanations for each candidate,” Lin said. “That is what Hubble has allowed us to do for our candidate.”
One of the curious things about J2150−0551 was its location – not in the centre of a galaxy, where you normally find large black holes tearing apart stars. In fact, it seemed to come from a star cluster on the outskirts of a lenticular galaxy 800 million light-years away.
This is consistent with one of the formation models for intermediate-mass black holes that also explains why they’re so tricky to find.
A 2004 paper proposed that the gravity of a dense star cluster could cause the stars inside it to fall towards the cluster’s centre, forming a star as massive as thousands of Suns. This then would collapse under its own weight, forming an intermediate-mass black hole.
But, because it’s extremely hard to resolve individual stars outside the Milky Way, never mind tracking their orbits, black holes outside the Milky Way are only detectable when material, such as a star or a gas cloud, is actively falling into them.
By the time one of these star clusters had created a black hole, it would have cleared the area within its gravitational reach, meaning there’s no material left in its vicinity for it to devour, except for the rare and occasional stray star. This is what astronomers think J2150−0551 was caused by.
And there was still a possibility that J2150−0551 was something else – a neutron star inside the Milky Way that was cooling after being heated during an accretion outburst – slurping down material from another star. An accretion outburst large enough to cause this heating in a neutron star had not been detected in an all-sky survey that should have picked it up, but we needed a more conclusive ruling.
Hubble was pointed at the patch of sky in which J2150−0551 was seen to obtain deep, high-resolution imaging to confirm its location. These observations confirmed that the X-ray glow had not emanated from the Milky Way, but the star cluster 800 million light-years away.
Meanwhile, XMM Newton obtained more X-ray observations.
“Adding further X-ray observations allowed us to understand the total energy output,” said astronomer Natalie Webb of the Université de Toulouse in France. “This helps us to understand the type of star that was disrupted by the black hole.”
These observations led the researchers to conclude that the flare was caused by an intermediate-mass black hole as it captured, shredded and accreted a small, main-sequence star around a third of our Sun’s mass, and about 40 percent of its size.
They also found that the star cluster itself could be the core of a dwarf galaxy, stripped of most of its material due to gravitational interactions with the larger galaxy it borders.
Importantly, the finding reaffirms that star clusters orbiting more massive galaxies could be a prime location for finding these elusive intermediate-mass black holes.
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.
