Connect with us


Planet-forming disks with misaligned rings discovered in multi-star system



Sept. 3 (UPI) — Astronomers have discovered misaligned rings within the planet-forming disk surrounding a faraway, triple-star system, according to a study published Thursday in the journal Science.

Scientists suspect the disk was disrupted by the gravitational pull from one of the three stars.

The trio of stars that form GW Orionis are located approximately 1,300 light-years from Earth. The system is noted for its giant protoplanetary disk.

Recently, astronomers were able to confirm the disk’s misalignment using observations by the Atacama Large Millimeter/submillimeter Array, a powerful observatory in Chile.

By studying how the massive planet-forming disk came to be misaligned, researchers hope to better understand how planets around multi-star systems form and evolve.

“The idea that planets form in neatly-arranged, flat disks around young stars goes back to the 18th century and Kant and Laplace,” Stefan Kraus told UPI in an email.

“The GW Ori images reveal an extreme case where the disk is not flat at all, but is warped and has a misaligned ring that has broken away from the disk and that is now precessing around the stars,” said Kraus, an astronomer at the University of Exeter.

Kraus and his research partners suggest GW Orionis and its off-kilter protoplanetary disk rings are interesting for a few different reasons. For one, the system is rare.

While many exoplanets have been found orbiting binary star systems, very few have been found circling systems with three or more stars. What’s more, exoplanets surrounding multi-star systems typically orbit very close to their host stars.

“The disk structures in GW Orionis, on the other hand, extend out to 400 [astronomical unites], or more than 10-times the separation of Neptune from the sun,” Kraus said. “So the system has the potential to form circumtriple planets on very wide orbits.”

Researchers were able to identify the misalignment of the disk’s rings by analyzing the scattered light and shadows cast by the differently inclined rings of dust.

“Shadows on disks have been observed before, but to my knowledge this is the first case where we resolve the ring casting the shadow,” Kraus said. “Also, one is used to seeing ‘straight’ shadows on disk — here, we have the extraordinary case that the shadow apparently ‘changes’ direction due to the strong curvature in the inner warped region of the disk.”

Scientists ran simulations to better understand how the triple-star system’s disk came to be warped and misaligned. The simulations suggest the gravitational torque exerted by the three stars created a tearing effect in the ring.

As a result of the tearing effect, scientists predict GW Orionis will birth a variety of exoplanets with oblique orbits — orbits askew from the equators of their host stars.

“We predict that many planets on oblique, wide-separation orbits will be discovered in future planet imaging surveys,” Kraus said.

Thanks to the analysis by Kraus and his colleagues, astronomers now know the 3D orientation of the system’s protoplanetary disk, as well as the properties of all three stars, making GW Orionis an ideal model for the study of exoplanet formation.

“This makes GW Ori a benchmark for studying body-disk interactions in general, which will advance our understanding of planet formation as well,” he said.

Source link

Continue Reading
Click to comment

Leave a Reply

Your email address will not be published. Required fields are marked *


Space agency leaders call for greater international cooperation



NASA Astronaut Chris Cassidy, serving as commander of the Expedition 63 mission aboard the International Space Station, took these photos of Hurricane Laura as it continued to strengthen in the Gulf of Mexico on August 25. Photo courtesy of NASA | License Photo

Source link

Continue Reading


Male lions form coalitions to protect territory, increase mating opportunities



Oct. 16 (UPI) — Male animals must compete with one another for food, territory and mates. Despite this, male lions prefer to work with one or more partners.

To better understand the how’s and why’s of coalition-building among lions, biologists from the Wildlife Institute of India and the University of Minnesota turned to the Asian lion, a single lion population confined to the forests of India’s Gir National Park.

In a previous study, researchers were able to show that lion pairs had greater access to mating opportunities and were better able protect their territories than solitary lions.

“However, a lack of genetic data from the population at this stage had prevented us from determining if such cooperation extended to relatives only, or whether non-kin were included as well,” Stotra Chakrabarti, a postdoctoral research associate at the University of Minnesota, said in a news release.

For the latest study, published Friday in the journal Scientific Reports, researchers combined behavioral and genetic records of known mothers, offspring and siblings to better estimate the level of relatedness between cooperating lions.

The lions of Gita don’t just form pairs. Some lions form coalitions of three or four males. Researchers found lion trios and quartets were consistently composed of brothers and cousins. Their analysis also showed more than 70 percent of pairs were formed by unrelated lions.

“Forgoing mating opportunities is generally a severe evolutionary cost, unless in doing so you help related individuals,” said study co-author Joseph Bump, associate professor at the University of Minnesota. “As a consequence, this evidence supports a conclusion that large male lion coalitions are feasible only when all partners are brothers and/or cousins.”

Researchers found larger coalitions fared best, but the fitness of individual lions, the number of possibly sired offspring, was greater among pairs.

“The results of our study show that male coalitions prosper better than loners in established lion societies and this can have crucial implications for their conservation, especially when establishing new populations through reintroductions,” said YV Jhala, principal investigator of the Gir lion project and the dean of the Wildlife Institute of India.

The integration of field observations and genetic data allowed scientists to identify new forms of coalition building, including one team of lions feature a father and sun duo.

Because siblings rarely reach maturity, researchers found larger coalitions are uncommon among Gir lions, making up just 12 to 13 percent of male teams.

Scientists also determined that among pairs, related lions weren’t more likely to support one another during fights than unrelated lions.

“This shows that kin support is not the only reason why males cooperate with each other, but kin support makes the cooperation even more beneficial,” Bump said.

Overall, the findings suggest cooperation among lions is quite complex — a topic ripe for further investigation.

“We have quantified the ultimate reasons why unrelated males team up, but it would be worthwhile to investigate other aspects of male cooperation, including how their bonds are forged in the first place, how they find compatible partners, what breaks the ice between them when they first meet and how they decide who will lead and who will follow,” lead study author Chakrabarti said.

Source link

Continue Reading


Ancient societies collapsed when leaders ignored the social contract



Oct. 16 (UPI) — When ancient societies formerly ruled by principles of good governance failed, they failed hard.

According to a new study published in the journal Frontiers in Political Science, ancient autocracies were less likely to last, but suffered less dramatic failures.

To better understand the role of government on the success and longevity of ancient societies, researchers took an in-depth look at principles that guided the governments of four societies: the Roman Empire, China’s Ming Dynasty, India’s Mughal Empire and the Venetian Republic.

Because free and fair elections were rare or nonexistent during ancient times, researchers had to come up with an alternative for gauging good governance.

“You can’t really measure it by the role of elections, so important in contemporary democracies,” study co-author Gary Feinman, the MacArthur curator of anthropology at Chicago’s Field Museum, said in a news release. “You have to come up with some other yardsticks, and the core features of the good governance concept serve as a suitable measure of that.”

“They didn’t have elections, but they had other checks and balances on the concentration of personal power and wealth by a few individuals,” Feinman said. “They all had means to enhance social well-being, provision goods and services beyond just a narrow few, and means for commoners to express their voices.”

For the ruling elite, good governance was a sensible choice. Most successful empires depended on taxes and resources from local economies, and thus their leaders had to meet the basic needs of their citizens.

“There are often checks on both the power and the economic selfishness of leaders, so they can’t hoard all the wealth,” Feinman said.

Researchers found societies with governments that were reasonably responsive to their people — governments that met the definition of good governance — tended to last a bit longer than autocratic governments.

However, researchers found that when good governments turned rotten, the breakup was often uglier than the collapse of autocratic governments.

According to the study, good governments fail more dramatically because the bureaucracy is more intimately integrated with society at large.

“Social networks and institutions become highly connected, economically, socially, and politically,” Feinman said. “Whereas if an autocratic regime collapses, you might see a different leader or you might see a different capital, but it doesn’t permeate all the way down into people’s lives, as such rulers generally monopolize resources and fund their regimes in ways less dependent on local production or broad-based taxation.”

Researchers also looked at why exactly good governments fail. They found the collapse of good governments was often triggered by the rise to power of amoral leaders — leaders who ignored the social contract and abandoned their society’s ideals.

Such betrayals often precipitated or accompanied rising inequality, concentration of political power, tax evasion, crumbling infrastructure and the decline of bureaucratic institutions — a pattern researchers suggest can be observed in modern societies.

“What I see around me feels like what I’ve observed in studying the deep histories of other world regions, and now I’m living it in my own life,” said Feinman. “It’s sort of like Groundhog Day for archaeologists and historians.”

Researchers suggest their findings are a reminder that even previously successful governments and prosperous, stable societies can fail when leaders abandon a society’s core principles.

“In the cases we address, calamity could very likely have been avoided, yet, citizens and state-builders too willingly assumed that their leadership will feel an obligation to do as expected for the benefit of society,” said lead study author Richard Blanton.

“Given the failure to anticipate, the kinds of institutional guardrails required to minimize the consequences of moral failure were inadequate,” said Blanton, a professor emeritus of anthropology at Purdue University.

Source link

Continue Reading