The region around the galaxy NGC 1052-DF4, taken by the IAC80 telescope at the Teide Observatory in … [+] Tenerife, Spain. The main galaxies in the field of view, include NGC 1052-DF4 (center of the image) and its neighbor NGC 1035 (center left).
M. Montes et al.
Dark matter theory has long been sacrosanct in mainstream astronomical circles. Rarely do astronomers contradict the tenet that some 85 percent of all matter in the cosmos is dominated by unseen matter that only weakly interacts with gravity.
Thus, it came as a surprise that doubt was cast on its existence by recent Hubble Space Telescope observations of two massive galaxies that appeared to be altogether devoid of this exotic matter.
But in a paper submitted to The Astrophysical Journal, an international team of scientists detail observations on NGC 1052-DF4, the second galaxy purported to harbor little or no such dark matter. They argue that NGC 1052-DF4, a massive galaxy some 45 million light years away in the southern constellation of Cetus, is being almost completely stripped of this strange matter via gravitational interactions with its nearby galactic neighbor, NGC 1035.
In fact, NASA asserts that the forces driving NGC 1035 to interfere with NGC 1052-DF4 are tearing the latter apart.
Deep optical imaging of NGC 1052-DF4 has revealed that this galaxy is undergoing tidal disruption, write the authors, caused by its interaction with its neighbor, NGC 1035. Dark matter is less concentrated than stars, and therefore during interactions is preferentially stripped from satellites galaxies, they report.
How does such stripping actually work?
Like the friction of chalk on a blackboard, Mireia Montes, a postdoctoral fellow at the University of New South Wales in Australia and the paper’s lead author, told me. As you write with the chalk, the chalk’s particles are deposited in the direction of your script, she says.
New data from the NASA/ESA Hubble Space Telescope provides further evidence for tidal disruption in … [+] the galaxy NGC 1052-DF4. Astronomers have concluded that the gravitational forces of the neighboring galaxy NGC 1035 stripped the dark matter from NGC 1052-DF4 and are now tearing the galaxy apart.
ESA/Hubble, NASA, Digitized Sky Survey 2; Acknowledgment: Davide de Martin
By rote, as the galaxy continues its interaction with its massive galactic neighbor, the stripped chalk particles would get deposited in the direction of the orbit of the galaxy, says Montes. In this case, what we can see that NGC 1052-DF4’s stars are actually beginning to be stripped from their host galaxy, she says.
Such research provides case studies in how and why large galaxies actually form. Dark matter helps to form galaxies as it provides sort of the gravitational well where ordinary matter can sit and cool down and form stars, says Montes.
It also acts as a protective shield. Without this dark matter shield, says Montes, the galaxy would be very unstable and prone to gravitational influence from external forces. Thus, she says, such galaxies wouldn’t survive in an environment where there are more massive galaxies would swallow up these dark matter-stripped galaxies.
We also know from simulations that the dark matter content has to decrease by some 90 percent for the interaction to start affecting the stars, she says.
These new more accurate observations also provided new distance measurements to the galaxy, NGC 1052-DF2. In 2018, a team of Yale University astronomers reported that NGC 1052–DF2 was also devoid of dark matter. But these new observations solve that mystery.
We argue instead that a closer distance to the galaxy than the one measured in 2018 solves the dark matter peculiarities of the NGC 1052-DF2 galaxy, says Montes. But a closer distance does not help in the case of NGC 1052-DF4; it’s still missing dark matter, she says.
And for physics as we know it to work, theorists still need dark matter.
Without the presence of dark matter, primordial gas would lack enough gravitational pull to start collapsing and forming new galaxies, says Montes. And once a galaxy is stripped of its dark matter, Montes says that this exotic matter ends up becoming part of galaxy responsible for the stripping. In this case, that would be the cigar-like, spiral galaxy NGC 1035.
“In time, NGC 1052-DF4 will be cannibalized by the large system around NGC 1035, with at least some of their stars floating free in deep space,” team member Ignacio Trujillo of the Instituto de Astrofísica de Canarias in Spain, said in a statement.
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.
