Rapid-forming giants could disrupt spiral protoplanetary discs

Rapid-forming giants could disrupt spiral protoplanetary discs
Protoplanetary disc with an orbiting planet. Credit: University of Warwick

Giant planets that developed early in a star system’s life could solve a mystery of why spiral structures are not observed in young protoplanetary discs, according to a new study by University of Warwick astronomers.


The research, published today in the Astrophysical Journal Letters andpart supported by the Royal Society, provides an explanation for the lack of spiral structure that astronomers expect to see in protoplanetary discs around young stars that also suggests that scientists may have to reassess how quickly planets form in a disc’s lifecycle.

Protoplanetary discs are the birthplaces of planets, harbouring the material that will eventually coalesce into the array of planets that we see in the Universe. When these discs are young they form spiral structures, with all their dust and material dragged into dense arms by the massive gravitational effect of the disc spinning. A similar effect occurs at the galactic level, hence why we see spiral galaxies such as our own, the Milky Way.

Over the course of three to ten million years material from the disc comes together to form planets, falls onto the star it is orbiting or just disperses into space through winds coming off the disc. When a disc is young it is self-gravitating, and the material within it forms a spiral structure which it loses when it becomes gravitationally stable. Young planets that develop then carve out gaps in the disc as they consume and disperse material in their way, resulting in the ‘ring and gap’ features that astronomers most commonly see in protoplanetary discs.

Video showing a protoplanetary disc’s evolution with an orbiting 3 Jupiter mass planet. Credit: University of Warwick

But astronomers have struggled to account for observations of young protoplanetary discs that show no signs of spirals, but instead look like a disc much older with a ring and gap structure. To provide an explanation, Sahl Rowther and Dr. Farzana Meru from the University of Warwick Department of Physics conducted computer simulations of massive planets in young discs to determine what would happen when they interacted.

They found that a giant planet, around three times the mass of Jupiter, migrating from the outer regions of the disc towards its star would cause enough disruption to wipe out the disc’s spiral structure with results much like the discs observed by astronomers. However, to be present in the spiral stage of the disc those planets would have to form rapidly and early in the disc’s lifecycle.

Lead author Sahl Rowther, Ph.D. student in the Department of Physics, said: “When discs are young, we expect them to be massive with spiral structures. But we don’t see that in observations.

“Our simulations suggest that a massive planet in one of these young discs can actually shorten the time spent in the self-gravitating spiral phase to one that looks more like some of the observations that astronomers are seeing.

Video showing the protoplanetary disc’s evolution without a planet. Credit: University
Read more

Arctic ‘Sleeping Giants’ Waking Up, Starting To Release Methane: Report

KEY POINTS

  • Scientists found evidence that the Arctic “sleeping giants” are starting to wake up
  • Preliminary findings provide evidence of methane deposits being released
  • The impact of the emissions is still unclear but it could be problematic for climate warming

A team of researchers found evidence that the “sleeping giants” of the Arctic Ocean may be starting to release methane. This could be problematic for an already warming planet.

Methane is a greenhouse gas that has a shorter lifespan than carbon dioxide but is much more potent at trapping radiation. As the U.S. Environmental Protection Agency (EPA) explained, “pound for pound,” methane’s impact is 25 times greater than that of carbon dioxide in a period of 100 years. 

In the Siberian Arctic coastal regions, there are methane hydrates or crystals of methane gas molecules that are trapped between the solid water molecules. Called “sleeping giants,” these methane hydrates could be a significant source of methane emission should they be released into the atmosphere.

Unfortunately, the findings of the researchers aboard the Russian Akademik Keldysh (RAK), shared in an exclusive report from The Guardian, show that the sleeping giants may be starting to wake up as high levels of methane have been detected in the Laptev Sea close to Russia.

As part of the International Siberian Shelf Study (ISSS-2020) expedition, the researchers monitored several areas on the Laptev Sea slope and found evidence that the methane is starting to be released.

They reportedly detected high methane levels being at depths of 350 meters. In one area at a depth of 300 meters, the researchers even found methane concentrations up to 1,600 nanomoles per liter, which is 400 times higher than expected, The Guardian said.

And although much of the “bubbles” were dissolving in the water, the researchers also noted high levels of methane on the surface.

“At this moment, there is unlikely to be any major impact on global warming, but the point is that this process has now been triggered,” scientist Örjan Gustafsson of Stockholm University told The Guardian via a satellite call from the vessel. “This East Siberian slope methane hydrate system has been perturbed and the process will be ongoing.”

Gustafsson noted the possible “awakening” of the sleeping giants in an earlier feature on the expedition from Stockholm University. He further explained that what and how the sleeping giants contribute to methane emissions is still “poorly understood.”

As The Guardian explains, it’s possible that the “instability” is likely caused by warmer waters from the Atlantic coming into the Arctic. What’s more, the temperatures in the area have been unusually warm.

This is problematic because having major greenhouse gases released from natural sources could expedite the planet’s warming process and further limit the amount of human-made greenhouse gases we can emit. It’s something that’s already quite the challenge even without the contributions from the major natural greenhouse gas sources.

Just this July, for instance, a major international study reported that methane emissions increased by 9% in the last decade,

Read more

Giants’ Joe Judge doesn’t commit to Andrew Thomas at left tackle after Matt Peart’s solid first career start

Giants head coach Joe Judge reiterated that Andrew Thomas’ benching to start the game against Washington on Sunday was a disciplinary benching, not performance related.

But after Matt Peart put together a solid game while splitting time with Thomas, is there any doubt that Thomas – the Giants’ fourth overall pick in this year’s draft — will be the starting at left tackle this Thursday against the Eagles?

It’s a legitimate question for Judge to consider, as Peart performed well in his 26 snaps at left tackle. In fact, Pro Football Focus graded him the highest of any Giants offensive player that was in for more than 25 snaps on Sunday. He had an 89.7 overall grade with a 93.4 run block grade. He also allowed one pressure in 11 pass block attempts.

When asked about the position for this upcoming game, Judge didn’t commit to Thomas returning to his normal starting job at left tackle.

“Yeah, we’ll go through practice this week and see how everything shakes out right now,” Thomas told reporters via Zoom. “But I was pleased with the way both he and Matt played along with Cam [Fleming]. We have multiple guys that can play the positions.”

That is typical Judge speak – not committing to anyone being a starter and earning it through practice and hard work. So maybe these couple of practices before the game will show Judge whether or not Thomas deserves another start over Peart. He did mention that every tackle gets reps on both sides of the offensive line to make sure they’re ready for anything.

It would be pretty telling, though, if Thomas was benched yet again for Peart to start at left tackle considering Thomas’ draft status and $32 million rookie deal. In the second half, Thomas was actually taken out of the game after allowing Montez Sweat to get around him quickly on a third-and-short run attempt that was a poor attempt at setting the edge and ended with Devonta Freeman not picking up the first down.

In Thomas’ defense, he has been going up against some of the best edge rushers in the league in the past few weeks like Bud Dupress, Demarcus Lawrence and Khalil Mack. Peart hasn’t had such luxury to battle with those NFL studs, but at the end of the day, this is the NFL and that’s the competition both players will be seeing on a weekly basis. 

Derek Barnett and Brandon Graham, two first-round pick themselves, are this week’s challenge. They have 7.5 total sacks between them in the last five weeks.

Still, Peart was drafted out of UConn in the third round and was considered a developmental player that had the potential to play a tackle position in the future. But his teammates are noticing during practice that he hasn’t been performing that way nor does he even seem like a rookie at all. His game against the Football Team further justified that thinking.

“He’s definitely a

Read more

Humans and climate drove giants of Madagascar to extinction

madagascar
Credit: Pixabay/CC0 Public Domain

Nearly all Madagascan megafauna—including the famous dodo bird, gorilla-sized lemurs, giant tortoises, and the Elephant Bird, which stood 3 meters tall and weighted close to a half ton—vanished between 1,500 and 500 years ago. Were these animals overhunted to extinction by humans? Or did they disappear because of climate change? There are numerous hypotheses, but the exact cause of this megafauna crash remains elusive and hotly debated.


The Mascarene islands east of Madagascar are of special interest because they are among the last islands on Earth to be colonized by humans. Intriguingly, the islands’ megafauna crashed in just a couple of centuries following human settlement. In a recent study published by Science Advances, a team of international researchers found that it was likely a “double whammy” of heightened human activities in combination with a particularly severe spell of region-wide aridity that may have doomed the megafauna. The researchers rule out climate change as the one and only cause, and instead suggest that the impact of human colonization was a crucial contributor to the megafaunal collapse.

Hanying Li, a postdoctoral scholar at the Xi’an Jiaotong University in China and the lead author of this study, pieced together a detailed history of the regional climate variations. The primary source of this new paleoclimate record came from the tiny Mascarene island of Rodrigues in the southwest Indian Ocean approximately 1600 km east of Madagascar. “[It is] an island so remote and small that one will not find it on most schoolbook atlases,” says Gayatri Kathayat, one of the co-authors and an associate professor of climate science at Xi’an Jiaotong University.

Analysis of Cave Deposits

Li and colleagues built their climate records by analyzing the trace elements and carbon and oxygen isotopes from each incremental growth layer of stalagmites, which they collected from one of the many caves on this island. The bulk of these analyses were conducted at the Quaternary Research Group at the Institute of Geology at the University of Innsbruck, led by Prof. Christoph Spötl.

Variations in the geochemical signatures provided the information needed to reconstruct the region’s rainfall patterns over the last 8000 years. To analyze the stalagmites, the researchers used the stable isotope method in their lab in Innsbruck. Despite the distance between the two islands, the summer rainfall at Rodrigues and Madagascar is influenced by the same global-wide tropical rain belt that oscillates north and south with the seasons. Hai Cheng, the study’s senior co-author, says, “And when this belt falters and stays further north of Rodrigues, droughts can strike the whole region from Madagascar to Rodrigues.”

Co-author Hubert Vonhof, scientist at Max Planck Institute of Chemistry in Mainz, Germany, says, “Li’s work from Rodrigues demonstrates that the hydroclimate of the region experienced a series of drying trends throughout the last eight millennia, which were frequently punctuated by ‘megadroughts’ that lasted for decades.”

Resilient to climate stress

The most recent of the drying trends in the region commenced around 1,500 years ago at

Read more