This is an artist’s concept of AB Aurigae b, a forming planet about 9 times as massive as Jupiter. The Hubble Space Telescope discovered this proto-planet. Image via NASA/ ESA/ Joseph Olmsted (STScI).
Most planets form by a relatively sedate process called core accretion. It’s basically smaller grains sticking together to make larger grains, until gravity takes over to pull the object into the shape of a ball. But there’s also evidence for a more “intense and violent” planet-forming process, called disk instability. And astronomers have long sought direct observations of this 2nd process, particularly for large gas giant exoplanets, similar to our solar system’s planet Jupiter. This month (April 4, 2022), astronomers announced a Hubble Space Telescope image of a Jupiter-like protoplanet (a planetary embryo) forming via disk instability.
The researchers published the peer-reviewed details of their discovery in Nature Astronomy on April 4.
View larger. | Here is the protoplanet AB Aurigae b as seen in Hubble Space Telescope images (marked by arrow). The images cover 13 years, using the telescope’s Space Telescope Imaging Spectrograph (STIS) and Near Infrared Camera and Multi-Object Spectrograph (NICMOS). Image via NASA/ ESA/ Thayne Currie (Subaru Telescope/ Eureka Scientific Inc.)/ Alyssa Pagan (STScI).
Hubble observes planet forming in an ‘unconventional way’
As described by the press release, this planet – named AB Aurigae b – is forming in an “unconventional way.” Why unconventional? It has long been thought that gas giant planets like Jupiter form from core accretion. In this process, small bits of material, ranging from dust to boulders, collide over time and stick together. This forms a central core, or protoplanet, which then accumulates additional material like dust and gas.
With disk instability, however, the planet forms directly from the protoplanetary disk around the star. This happens when the disk cools and breaks down into smaller planetary-mass fragments that then continue to accumulate material.
The planet that Hubble found appears to be the result of disk instability, not core accretion. Lead researcher Thayne Currie of the Subaru Telescope said:
Nature is clever; it can produce planets in a range of different ways.
New planet is 9 times more massive than Jupiter
The star system that harbors AB Aurigae b is still very young, only about two million years old. That’s like a baby compared to our solar system, which is about 4.6 billion years old. Its new protostar is approximately nine times the mass of Jupiter. It is also very far from its star, 8.6 billion miles to be exact. That’s more than twice the distance of Pluto from our sun.
That great distance also makes the core accretion formation scenario unlikely. The researchers say it would take a very long time, if ever, for a Jupiter-sized planet to form in that way, so far from its star. Therefore, the disk instability process is a better explanation to how the planet is forming. Hubble also observed a distinct spiral structure swirling around the newly-forming planet, also supporting the disk instability hypothesis.
Infant planets can be difficult to see in protoplanetary disks. There are complex features in the disks that could be mistaken for newly-forming planets like AB Aurigae b. So how did the researchers successfully distinguish this planet? They used two different Hubble instruments: the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrograph (NICMOS). Then, the researchers compared that data to data from the planet imaging instrument SCExAO on Japan’s 8.2-meter Subaru Telescope at the summit of Mauna Kea, Hawaii.
As Currie noted:
Interpreting this system is extremely challenging. This is one of the reasons why we needed Hubble for this project, a clean image to better separate the light from the disk and any planet.
As it happens, the disk of dust and gas AB Aurigae is tilted nearly face-on to our view from Earth. That also help the astronomers see the young planet better, with fewer obstructions.
Another factor was the age of Hubble itself. One or two years would be insufficient to determine if AB Aurigae b really was a new planet or not. But Hubble’s data, combined with that from Subaru, cover 13 years overall. Currie explained:
We could not detect this motion on the order of a year or two years. Hubble provided a time baseline, combined with Subaru data, of 13 years, which was sufficient to be able to detect orbital motion.
Hubble and Subaru
Now, there seems to be little doubt that this is indeed a new infant planet and not something else being misinterpreted. Olivier Guyon of the University of Arizona and Subaru Telescope added:
This result leverages ground and space observations and we get to go back in time with Hubble archival observations. AB Aurigae b has now been looked at in multiple wavelengths, and a consistent picture has emerged, one that’s very solid.
The Hubble Space Telescope as seen in space above Earth. Image via NASA/ Arizona Public Media.
New insights into the formation of giant planets
The Hubble observations are the first good evidence that gas giant planets can form from disk instability and not just core accretion. This provides new insights into how planets form overall, and shows that gravity is the main ingredient, whatever the process. As Alan Boss of the Carnegie Institution of Science explained:
This new discovery is strong evidence that some gas giant planets can form by the disk instability mechanism. In the end, gravity is all that counts, as the leftovers of the star-formation process will end up being pulled together by gravity to form planets, one way or the other.
This is just the latest exciting discovery from Hubble. Last week, researchers also announced that Hubble has discovered the most distant star ever seen so far. The star formed in the juvenile universe just 900 million years after the Big Bang.
Bottom line: Astronomers using the Hubble Space Telescope have, for the first time, observed a giant new planet forming around another star via disk instability. The infant world is nine times as massive as Jupiter.
Paul Scott Anderson has had a passion for space exploration that began when he was a child when he watched Carl Sagan’s Cosmos. While in school he was known for his passion for space exploration and astronomy. He started his blog The Meridiani Journal in 2005, which was a chronicle of planetary exploration. In 2015, the blog was renamed as Planetaria. While interested in all aspects of space exploration, his primary passion is planetary science. In 2011, he started writing about space on a freelance basis, and now currently writes for AmericaSpace and Futurism (part of Vocal). He has also written for Universe Today and SpaceFlight Insider, and has also been published in The Mars Quarterly and has done supplementary writing for the well-known iOS app Exoplanet for iPhone and iPad.
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.
