Astronomers will be able to figure out what kind of stars interstellar objects such as ‘Oumuamua come from, and therefore something about their compositions, based on their velocity as they enter our solar system, new research suggests.
So far, astronomers have discovered only two confirmed interstellar objects (ISOs) in our solar system, ‘Oumuamua and 2I/Borisov. They couldn’t have been more different from one another: ‘Oumuamua lacked any kind of cometary tail, whereas Borisov looked like a typical comet.
However, the properties of their home planetary systems are imprinted on both of them, said grad student Matthew Hopkins of the University of Oxford in England, who conducted the new research and presented it at the U.K.’s National Astronomy Meeting in early July.
“Because they come from other stars, their properties are going to correlate with those stars,” Hopkins told Space.com.
Though we’ve only spotted two ISOs to date, it’s expected that thousands of them are passing through our solar system at any given time, most too far away from us to be detected. However, most or all of those ISOs likely began life as comets around other stars, before an encounter with a Jupiter-sized planet, or perhaps a fly-by star, ejected them into interstellar space.
In our solar system, “for every one comet that Jupiter [and Neptune] pushed into the Oort Cloud, it completely ejected 10, and there are a trillion objects in the Oort Cloud,” said Hopkins. Doing the math, it is easy to come to the conclusion that ISOs “are the most numerous objects in the Milky Way galaxy.”
Moving groups of interstellar objects
Each star is moving around the galaxy at its own pace, and together they form moving groups that are related to their point of origin, which, in turn, corresponds with their intrinsic chemistry.
The stars with the most heavy elements, such as our sun, live in the “thin disk” of the galaxy, a plane in the spiral arms about 400 light-years thick. Surrounding it is the “thick disk,” which can stretch as high as 1,000 light-years above the plane of the galaxy and contains mostly older stars with fewer heavy elements.
The populations of stars belonging to each disk have different velocity distributions. Because the ISOs that they eject share a similar velocity as their parent star relative to the sun, they tend to stick to the same moving groups, but these moving groups criss-cross the sun’s path all the time.
“The sun is essentially running into them,” said Hopkins. This means that we should preferentially expect to see ISOs coming from the “solar apex,” which is the direction of the sun’s motion relative to other nearby stars.
“‘Oumuamua was very close to the solar apex,” Hopkins said. “Borisov was slightly farther away but still quite near [to the solar apex], and that’s where we expect most of them to come from.”
Coming from this direction means that they’ll make their closest approach to the sun, where they are easiest to detect, while they are in the Southern Hemisphere sky — the same sky that the new Vera Rubin Observatory will be surveying. It is expected that Vera Rubin will discover hundreds of new ISOs.
Slower ISOs contain less water
The lower an ISO’s relative velocity compared to the sun, the more likely it is that it will fall into the inner solar system where we can detect it; the fast ones will just speed through without necessarily being attracted much by the sun’s gravity. An ISO’s relative velocity is related to the relative velocity of its parent star, which depends significantly on whether that star hails from the thin disk with more heavy elements, or from the thick disk with fewer heavy elements.
“My results show that the velocity of an ISO correlates with its composition, and because of this we can get a handle on the types of star they may have come from,” said Hopkins.
The lower-velocity ISOs (relative to the sun) are expected to come from the thin disk, where stars and their accompanying planetary systems form from gas and dust that contain more heavy elements. The more heavy elements there are in the disk of gas and dust that forms planets and comets, the smaller the fraction of water an ISO will have.
This is because a protoplanetary disk rich in heavier elements contains a lot of carbon, and carbon (as well as iron, magnesium, silicon and sulfur) is adept at plucking up all the free oxygen atoms, two at a time, to form molecules of carbon dioxide. Water can only form from any oxygen atoms that are left over, meaning that ISOs forming within these disks generally possess a lower fraction of water.
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Could this lack of water explain why ‘Oumuamua did not display a cometary tail?
“Because it had a lower velocity relative to the sun, it probably did come from a thin disk star with more heavy elements,” said Hopkins. However, he is keen to point out the caveat that we don’t know ‘Oumuamua’s history — it could have lost its water and other volatile elements some other way. Perhaps they were eradicated by cosmic rays while traveling through interstellar space, for example, or by too many close passes to its parent star before it was ejected.
Borisov, on the other hand, was in the middle range for water content based on spectral observations of its tail.
With currently only two examples of ISO, it is difficult to draw too many conclusions. However, once the Vera Rubin Observatory is up and running later this decade, the hundreds of ISOs that it should find will be able to provide a fuller picture of where they are coming from and what their chemical properties are.
“If there’s a bias towards ISOs moving similarly to the sun falling into the inner solar system, then we would expect to see more ISOs from the thin disk,” said Hopkins.
That might mean we’ll see more objects similar to ‘Oumuamua rather than Borisov. Only time will tell how correct that prediction is.
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.
