The latest observations of Betelgeuse show that the star is now beginning to slowly brighten. No supernova today! Nothing to see, better luck next time.
Despite some of the hype, this behavior is exactly what astronomers expected. Betelgeuse is a very different star from our Sun. While our Sun is a main-sequence star in its prime of life, Betelgeuse is a red giant star on the verge of death. But the death of a star is not a simple process.
The rate of energy production by nuclear fusion in a star. Credit: R J Hall
Stars shine so brightly and for so long because of a delicate balance of gravity and nuclear fusion. Gravity would like to collapse a star under its weight. Without nuclear fusion, gravity would crush a star into a white dwarf, neutron star, or black hole. But the crushing pressure gravity creates allows hydrogen in the star’s core to fuse into helium. The process is known as the proton-proton chain (or pp-chain) and combines four hydrogen nuclei into one helium nucleus. About 3% of the original mass is converted to energy in the form of gamma rays. This energy heats the core even further, letting it push back against gravity.
For stars larger than the Sun, another fusion process known as the CNO cycle kicks in. CNO stands for Carbon-Nitrogen-Oxygen because the process fuses helium into those three elements. This process is why those three elements are the most abundant in the universe except for hydrogen and helium.
Illustration of a CNO cycle. Credit: Antonio Ciccolella
While both the pp-chain and CNO cycle can occur at the same time within a star, over time the CNO cycle increases as hydrogen become more scarce and helium more abundant. Since the CNO cycle releases more energy at a faster rate than the pp-chain, this means a star’s temperature increases over time. We see this gradual heating in our own Sun. By the time the CNO cycle dominates in a star, it’s core is so hot that the outer layers of a star swell and expand.
This is the stage Betelgeuse is in now. For millions of years, it was a main-sequence star of about 20 solar masses. But it is now fusing helium so furiously that it has bloomed into a red supergiant. Betelgeuse is running out of fuel, and in the end, gravity will win. It’s only a matter of time.
This comparison image shows the star Betelgeuse before and after its unprecedented dimming. The observations, taken with the SPHERE instrument on ESO’s Very Large Telescope in January and December 2019, show how much the star has faded and how its apparent shape has changed.
But that time isn’t necessarily soon. Betelgeuse has enough helium to stay in the red supergiant stage for about 100,000 years. Even after it runs out of helium, it will be able to fuse carbon into heavier elements for about a millennium. After that things will change fairly quickly. When it runs out of carbon it will try fusing heavier and heavier elements for about a year. Then its core will collapse, Betelgeuse will become a supernova, and we will finally get our show.
As best we can tell, Betelgeuse is still deep in the red supergiant phase of its life. Even though it has dimmed significantly of recent, it isn’t on the verge of exploding. The gradual dimming and brightening we see suggest that it won’t be exploding in our lifetimes. It suggests that the core of Betelgeuse is still chugging away at a steady pace.
The brightness of Betelgeuse over the years. Credit: AAVSO
The changing brightness of Betelgeuse is due to a process known as convection. The upper layers of the star are heated by the core, and this generates a flow of hotter and cooler regions. Material in the interior is heated and rises to the surface. It then cools and sinks into the star, and the cycle continues. Convection happens in the outer regions of most stars, including our Sun. On the surface of the Sun, these convection regions are known as granules, and they are typically the size of Texas. That sounds large, but for the Sun that’s smaller than most sunspots. So even though the Sun has bright hot regions and dimmer cool regions, they are so small compared to the Sun’s surface there isn’t an overall change in solar luminosity.
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A simulation of convection in Betelgeuse.
But the outer layer of Betelgeuse is much less dense than that of the Sun. It is even less dense than Earth’s atmosphere. It’s basically a thin soup of glowing gas. That means the convection regions on Betelgeuse can be huge. A single region can cover a large part of the star. When one of those regions rises to the top, Betelgeuse gets brighter, and when it cools the star dims. Betelgeuse is starting to brighten because hot material is convecting to its surface. This is normal for Betelguese and is likely the way things will be for millennia.
So no boom today. But boom someday. Sooner or later…Boom!
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.
