Data collected by an observatory in Antarctica has produced our first view of the Milky Way galaxy through the lens of neutrino particles. It’s the first time we have seen our galaxy “painted” with a particle, rather than in different wavelengths of light.
The result, published in Science, provides researchers with a new window on the cosmos. The neutrinos are thought to be produced, in part, by high-energy, charged particles called cosmic rays colliding with other matter. Because of the limits of our detection equipment, there’s much we still don’t know about cosmic rays. Therefore, neutrinos are another way of studying them.
It has been speculated since antiquity that the Milky Way we see arching across the night sky consists of stars like our Sun. In the 18th century, it was recognised to be a flattened slab of stars that we are viewing from within. It is only 100 years since we learnt that the Milky Way is in fact a galaxy, or “island universe”, one among a hundred billion others.
In 1923, the American astronomer Edwin Hubble identified a type of pulsating star called a “Cepheid variable” in what was then known as the Andromeda “nebula” (a giant cloud of dust and gas). Thanks to the prior work of Henrietta Swan Leavitt, this provided a measure of the distance from Earth to Andromeda.
This demonstrated that Andromeda is a far away galaxy like our own, settling a long-running debate and completely transforming our notion of our place in the universe.
Opening windows
Subsequently, as new astronomical windows have opened on to the sky, we have seen our galactic home in many different wavelengths of light –- in radio waves, in various infrared bands, in X-rays and in gamma-rays. Now, we can see our cosmic abode in neutrino particles, which have very low mass and only interact very weakly with other matter – hence their nickname of “ghost particles”.
Neutrinos are emitted from our galaxy when cosmic rays collide with interstellar matter. However, neutrinos are also produced by stars like the Sun, some exploding stars, or supernovas, and probably by most high-energy phenomena that we observe in the universe such as gamma-ray bursts and quasars. Hence, they can provide us an unprecedented view of highly energetic processes in our galaxy – a view that we can’t get from using light alone.
A digital operating module, part of the IceCube observatory, being lowered into the ice. Mark Krasberg, IceCube/NSF, Author provided
The new breakthrough detection required a rather strange “telescope” that is buried several kilometres deep in the Antarctic ice cap, under the South Pole. The IceCube Neutrino Observatory uses a gigatonne of the ultra-transparent ice under huge pressures to detect a form of energy called Cherenkov radiation.
This faint radiation is emitted by charged particles, which, in ice, can travel faster than light (but not in a vacuum). The particles are created by incoming neutrinos, which come from cosmic ray collisions in the galaxy, hitting the atoms in the ice.
Cosmic rays are mainly proton particles (these make up the atomic nucleus along with neutrons), together with a few heavy nuclei and electrons. About a century ago, these were discovered to be raining down on the Earth uniformly from all directions. We do not yet definitively know all their sources, as their travel directions are scrambled by magnetic fields that exist in the space between stars.
Deep in the ice
Neutrinos can act as unique tracers of cosmic ray interactions deep in the Milky Way. However, the ghostly particles are also generated when cosmic rays hit the Earth’s atmosphere. So the researchers using the IceCube data needed a way to distinguish between the neutrinos of “astrophysical” origin – those originating from extraterrestrial sources – and those created from cosmic ray collisions within our atmosphere.
The researchers focused on a type of neutrino interaction in the ice called a cascade. These result in roughly spherical showers of light and give the researchers a better level of sensitivity to the astrophysical neutrinos from the Milky Way. This is because a cascade provides a better measurement of a neutrino’s energy than other types of interactions, even though they they are harder to reconstruct.
Analysis of ten years of IceCube data using sophisticated machine learning techniques yielded nearly 60,000 neutrino events with an energy above 500 gigaelectronvolts (GeV). Of these, only about 7% were of astrophysical origin, with the rest being due to the “background” source of neutrinos that are generated in the Earth’s atmosphere.
The hypothesis that all the neutrino events could be due to cosmic rays hitting the Earth’s atmosphere was definitively rejected at a level of statistical significance known as 4.5 sigma. Put another way, our result has only about a 1 in 150,000 chance of being a fluke.
This falls a little short of the conventional 5 sigma standard for claiming a discovery in particle physics. However, such emission from the Milky Way is expected on sound astrophysical grounds.
With the upcoming enlargement of the experiment – IceCube-Gen2 will be ten times bigger – we will acquire many more neutrino events and the current blurry picture will turn into a detailed view of our galaxy, one that we have never had before.
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.
