The glorious, billowing Southern Ring Nebula is the cocoon of a dying star — and it has a secret. Scientists have found this nebula to exhibit a double-ring structure that evidences not one, but possibly three stars at its heart.
The Southern Ring Nebula, also designated NGC 3132, is a planetary nebula located about 2,000 light-years away in the constellation of Vela, the Sails. The name “planetary nebula” is a misnomer — such nebulas have nothing to do with planets. Instead, they are the final exhalations of dying, sun-like stars, which transform inside the nebulous chrysalis until finally blossoming into a white dwarf. A nebula is formed from the dying star’s outer envelope, which is puffed off into space following the star’s red giant phase.
The Southern Ring Nebula was imaged in December 2022 by the James Webb Space Telescope (JWST), which revealed molecular hydrogen gas forming the nebula’s “exoskeleton.” This refers to warm gas radiating with a temperature equal to about 1,000 kelvin (1,340 degrees Fahrenheit, or 726 degrees Celsius) as it gets illuminated and heated by ultraviolet light coming from the white dwarf itself. That exoskeleton, however, only represents a small fraction of the molecular gas in the nebula.
A team led by Joel Kastner of the Rochester Institute of Technology went hunting for more of the nebula’s molecular gas, specifically searching for carbon monoxide gas using the Submillimeter Array (SMA), which is a group of eight radio telescopes on an inactive volcano named Mauna Kea in Hawaii. Carbon monoxide is mixed in with hydrogen and other molecular gases inside the nebula, so observing the carbon monoxide content is actually a proxy for observing all those other molecules that are not as easy to detect. Sure enough, the SMA was able to measure both the distribution and velocities of the carbon monoxide molecules, showing which parts are moving towards us and which are moving away from us.
“JWST showed us the molecules of hydrogen and how they stack up in the sky, while the Submillimeter Array shows us the carbon monoxide that is colder that you can’t see in the JWST image,” said Kastner in a press statement.
As the Southern Ring’s name suggests, it is primarily shaped (from our point of view) as a ring. The SMA observations showed that this ring is expanding, which is to be expected as the nebula slowly grows before eventually dispersing. However, the data also allowed Kastner’s team to create a three-dimensional map of the nebula’s molecular exoskeleton. This offered up a surprise. Not only were the researchers able to show that what we see as a ring is merely a lobe in a bi-polar nebula seen end-on, but they also found a second ring perpendicular to the first.
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“When we started to turn the whole nebula around in 3D, we immediately saw it was really a ring, and then we were amazed to see there was another ring,” said Kastner.
The whole bizarre arrangement paints a fascinating tail of not one, not even two, but quite possibly three stars at the heart of the nebula. Only one of these stars, the most massive of the three, will have reached the end of its life — but the stellar trio, if all three really exist, are likely either too close to one another or too faint to be separately resolved, even by the JWST.
A composite near- and mid-infrared JWST image of the Southern Ring Nebula. (Image credit: NASA/ESA/CSA/STScI/O. De Marco (Macquarie University)/J. DePasquale (STScI))
There’s growing evidence that some planetary nebulas, at least those that sport complex structures, are formed from the interference of a companion star to the central dying star. For the Southern Ring, Kastner’s team posits that a triple system formed of a close binary is orbited by a more distant, third star within an orbital radius of 60 astronomical units of the binary (one astronomical unit, AU, is the distance between Earth and the sun, and in our solar system 60 AU would be out at the far edge of the Kuiper Belt).
The two lobes of the Southern Ring have a narrow, or “pinched,” waistline, like an hourglass, which is a common feature of planetary nebulas emanating from a binary star system in which one of the stars is reaching the end of its life. The binary companion is able to corral the material shed by the dying star so that it escapes along a polar, rather than equatorial, direction, forming the two lobes. The JWST’s mid-infrared observations support this hypothesis, having found an excess of infrared light coming from the central star system, which is a classic signature of a dusty disk formed from interactions between the red giant and a close binary companion.
So, that explains the first ring. The origin of the second ring, the team says, is less certain.
Though the Southern Ring appears bi-lobed, some material must have been emitted as a roughly spherical or ellipsoidal envelope of material cast off by the red giant, a rapid mass-loss event that perhaps represented its final exhalation of material to leave behind the white dwarf. The binary star system produces a series of fast, narrow jets, but if a third star is present, then the extra star’s gravity would act on the inner binary, causing the direction of the jets to “wobble,” like a spinning top. Those precessing jets would have carved out a circular hollow in the ellipsoidal component of the nebula, thereby creating the second ring.
Kastner emphasizes that this explanation is still speculative, but the nebula’s central ionized cavity does bear the evidence of such jets in its structure.
Other ring-shaped planetary nebulas, such as the Helix Nebula (NGC 7293 in Aquarius), have also been shown to have bi-lobed structures by which we are looking “down” the end of one lobe. The discovery of the second ring in the Southern Ring Nebula — or should that now be Southern Rings, plural? — is prompting astronomers to revisit some of those other well-known ring nebulas to see if they have missed second rings in them, too.
Planetary nebulas don’t just signify stellar death. They also hold the promise of new life — literally, in a sense.
“Where does the carbon and the oxygen and the nitrogen in the universe come from?” wonders Kastner. “We’re seeing it generated in the sun-like stars that are dying, like the star that’s just died and created the Southern Ring.”
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As an expanding planetary nebula disperses into interstellar space, it spreads those molecules across the cosmos, where they wind up in giant molecular clouds that form the next generation of stars and planets.
“A lot of that molecular gas would wind up in planetary atmospheres and atmospheres can enable life,” says Kastner. Indeed, all the elements on Earth heavier than hydrogen and helium originated inside stars and were then ejected into space when those stars died.
We are literally star-stuff, as many experts like to say.
So, when we marvel at the beauty of stellar death in nebulas such as the Southern Ring, we can also imagine it as a stellar phoenix to one day rise from the ashes and begin the cycle of star-birth and death all over again. To quote Battlestar Galactica, all this has happened before, and all of this will happen again.
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.
