The Milky Way has a big newfound black hole, and it lurks close to Earth! This sleeping giant was discovered with the European space telescope Gaia, which tracks the motion of billions of stars in our galaxy.
Stellar-mass black holes are created when a large star runs out of fuel and collapses. The new discovery is a landmark, representing the first time that a big black hole with such an origin has been found close to Earth.
The stellar-mass black hole, designated Gaia-BH3, is 33 times more massive than our sun. The previous most massive black hole of this class found in the Milky Way was a black hole in an X-ray binary in the Cygnus constellation (Cyg X-1), whose mass is estimated to be around 20 times that of the sun. The average stellar-mass black hole in the Milky Way is about 10 times heftier than the sun.
Gaia-BH3 is located just 2,000 light years from Earth, making it the second-closest black hole to our planet ever discovered. The closest black hole to Earth is Gaia-BH1 (also discovered by Gaia), which is 1,560 light-years away. Gaia-BH1 has a mass around 9.6 times that of the sun, making it considerably smaller than this newly discovered black hole.
“Finding Gaia BH3 is like the moment in the film ‘The Matrix’ where Neo starts to ‘see’ the matrix,” George Seabrook, a scientist at Mullard Space Science Laboratory at University College London and a member of Gaia’s Black Hole Task Force, said in a statement sent to Space.com. “In our case, ‘the matrix’ is our galaxy’s population of dormant stellar black holes, which were hidden from us before Gaia detected them.”
Seabroke added that Gaia BH3 is an important clue to this population, because it is the most massive stellar black hole found in our galaxy.
Of course, Gaia-BH3 is a small fry compared to the supermassive black hole that dominates the heart of the Milky Way, Sagittarius A* (Sgr A*), which has a mass 4.2 million times that of the sun. Supermassive black holes like Sgr A* aren’t created by the deaths of massive stars but rather by mergers of progressively larger and larger black holes.
A diagram showing the location of the three black holes discovered by Gaia (Image credit: ESA/Gaia Collaboration)
Sleeping giant black hole caused stellar companion to throw a wobbly
All black holes are marked by an outer boundary called an event horizon, at which point the black hole’s escape velocity exceeds the speed of light. That means an event horizon is a one-way light-trapping surface beyond which no information can escape.
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As a result, black holes don’t emit or reflect light, meaning they can only be “seen” when they are surrounded by material that they gradually feed on. Sometimes, this means a black hole in a binary system pulling material from a companion star, which forms a disk of gas and dust around it.
The tremendous gravitational influence of black holes generates intense tidal forces in this surrounding matter, causing it to glow brightly with material that is destroyed and consumed, also emitting X-rays. Additionally, the material the black hole doesn’t feast on can be channeled to its poles and blasted out as near-light speed jets, which are accompanied by the emission of light.
All of these light emissions can allow astronomers to spot black holes. The question is, how can “dormant” black holes that aren’t feeding on gas and dust around them be detected? For instance, what if a stellar-mass black hole has a companion star, but the two are too widely separated for the black hole to snatch stellar matter from its binary partner?
In cases like this, the black hole and its companion star orbit a point that represents the system’s center of mass. This is also the case when a star is orbited by a light companion, such as another star or even a planet.
Orbiting the center of mass results in a wobble in the motion of the star, which is visible to astronomers. Because Gaia is adept at precisely measuring the motion of stars, it is the ideal instrument to see this wobble.
Gaia’s Black Hole Task Force set about looking for odd wobbles that couldn’t be accounted for by the presence of another star or a planet and that indicated a heavier companion, possibly a black hole.
The region around the black hole Gaia-BH3. (Image credit: ESO/Digitized Sky Survey 2. Acknowledgement: D. De Martin.)
Homing in on an old giant star in the constellation Aquila, located 1,926 light-years from Earth, the team found a wobble in the star’s path. That wobble suggests that the star is locked in orbital motion with a dormant black hole of exceptionally high mass. The two are separated by a distance that ranges from the distance between the sun and Neptune at their widest and our star and Jupiter at their closest.
“It’s a real unicorn,” lead researcher Pasquale Panuzzo of CNRS, Observatoire de Paris in France, said in a statement. “This is the kind of discovery you make once in your research life. So far, black holes this big have only ever been detected in distant galaxies by the LIGO-Virgo-KAGRA collaboration, thanks to observations of gravitational waves.”
Three stellar-mass black holes in our galaxy: (left) Gaia BH1, (middle) Cygnus X-1, and (right) Gaia BH3, whose masses are 10, 21, and 33 times that of the sun, respectively. Gaia BH3 is the most massive stellar black hole found to date in the Milky Way. (Image credit: ESO/M. Kornmesser)
Thanks to the sensitivity of Gaia, the Black Hole Task Force was also able to put constraints on the mass of Gaia-BH3, finding it to possess 33 solar masses.
“Gaia-BH3 is the very first black hole for which we could measure the mass so accurately,” said Tsevi Mazeh, a scientist and Gaia collaboration member at Tel Aviv University. “At 30 times that of our sun, the object’s mass is typical of the estimates we have for the masses of the very distant black holes observed by gravitational wave experiments. Gaia’s measurements provide the first undisputable proof that [stellar-mass] black holes this heavy do exist.”
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However, the Gaia-BH3 system is bound to be of great interest to scientists for more than just its proximity to Earth and the mass of its black hole.
The star in this system is a sub-giant star that is around five times as large as the sun with 15 times its brightness, though it is cooler and less dense than our star. The Gaia-BH3 companion star is mainly composed of hydrogen and helium, the universe’s two lightest elements, lacking heavier elements, which astronomers (somewhat confusingly) call “metals.”
The fact that this star is “metal-poor” suggests that the star that collapsed and died to create Gaia-BH3 also lacked heavier elements. Metal-poor stars are expected to shed more mass than their more metal-rich counterparts during their lives, so scientists have questioned if they can maintain enough mass to birth black holes. Gaia-BH3 represents the first hint that metal-poor stars can indeed do so.
“Gaia’s next data release is expected to contain many more, which should help us to ‘see’ more of ‘the matrix’ and to understand how dormant stellar black holes form,” Seabroke concluded.
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.
