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‘Oumuamua was an iceberg of molecular hydrogen, scientists claim

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June 9 (UPI) — Ever since scientists spotted ‘Oumuamua, the solar system’s first documented interstellar visitor, there has been some debate over whether the object was a comet or an asteroid.

Now, astronomers argue ‘Oumuamua was a neither a comet nor an asteroid, but a new type of object.

“We hypothesize in the paper that ‘Oumuamua was a hydrogen iceberg,” Darryl Seligman, postdoctoral research fellow at the University of Chicago, told UPI in an email.

Seligman and his research partner, Gregory Laughlin of Yale University, published their hypothesis on Tuesday in the Astrophysical Journal Letters.

By the time astronomers first saw ‘Oumuamua, it was already headed on its way back toward interstellar space, but scientists were able to make out its shape, clock its spin rate and calculate its mass.

While initial analysis of the object’s trajectory suggested it moved like a comet, ‘Oumuamua didn’t look like one. It didn’t have a tail and it was dark.

To better understand the object’s composition, Seligman and Laughlin took a closer look at ‘Oumuamua’s movement through our solar system. Observations revealed a slight acceleration on the object’s path away from the sun, a surprise.

Fighting against the sun’s gravitational pull should have caused a slight slowdown, not an acceleration. Seligman and Laughlin determined that the acceleration was most likely caused by outgassing.

“What happens is that a comet has ice, or volatiles, on the surface,” Seligman said. “When the comet gets close enough to the sun, the photons from the sun can provide enough energy to sublimate the ice.”

Once the sun’s heat severs the bonds between molecules in the ice, the solar energy begins to quickly excite the now gaseous molecules.

“Now, this gas produces an outflow, in which the molecules explode off of the surface of the sun away from the comet, generally in the direction of the sun,” Seligman said. “By the conservation of momentum, this outflow will also back react on the comet, and push it away from the sun. We see this type of behavior in solar system comets all of the time.”

The outgassing of ‘Oumuamua was different than most comets, however. The interstellar visitor was without a tail, or coma, and the object’s acceleration was too great to be explained by water ice.

When Seligman and Laughlin looked for better candidates, they settled on molecular hydrogen. Their calculations showed the outgassing of modest amounts of molecular hydrogen ice would produce sharp acceleration without yielding a visible coma.

The discovery has implications for tracking down ‘Oumuamua’s cosmic origins.

“Molecular hydrogen ice is a weird thing to think about, simply because H2 will sublimate at approximately 6 degrees Kelvin, which is only a few degrees above the cosmic microwave background at 2.7 Kelvin,” Seligman said.

“So there are not many places in the universe that are thought to be able to get cold enough to freeze out hydrogen,” Seligman said. “Certainly, you won’t be finding frozen hydrogen most places in a protoplanetary disk where comets and asteroids form.”

The best place to find molecular hydrogen ice is someplace really cold, like inside a failed stellar core in a giant molecular cloud, some of the coldest, densest places in the universe.

Seligman and Laughlin hypothesize that what’s called a prestellar core, a dense orb of star-making material, failed to generate fusion. Without fusion, the core remained especially cold and accumulated chunks of hydrogen ice that were eventually ejected into interstellar space.

Such an origin story not only explains ‘Oumuamua’s acceleration through our solar system, but also its unusual baguette-like shape.

The weathering of a hydrogen iceberg would naturally produce an especially oblong object. When it passed through our solar system, ‘Oumuamua was six times longer than it was wide. Seligman likened the process to using a bar of soap.

“You start with a bar of soap which is somewhat elongated, maybe 2:1, and as you continuously use it, you take off roughly equal amounts of soap everywhere,” Seligman said. “So you always take a larger percentage of soap from the small axis as the long axis.”

“This continuous removal of material evenly off of the surface naturally produces a smaller but more elongated object,” he said. “That is what we envisioned happened to Oumuamua, but instead of soap, it was hydrogen coming off the surface, both due to the solar photons and the galactic cosmic rays that were hitting it after it was ejected from the Giant Molecular Cloud.”

The hypothesis proferred by Seligman and Laughlin, however, can’t be directly proven. To better understand ‘Oumuamua, scientists need to start by detecting and studying a lot more instrestellar objects — specifically, hydrogen icebergs — the researchers said. And they need to find them before they make their closest apporach to the sun.

But, according to Seligman, the ultimate goal is to acquire material samples.

“I think advocating for an interception mission to an interstellar object is an important next step,” he said.



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Sounds made by fluttering feathers help fork-tailed flycatchers communicate

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Sept. 22 (UPI) — Scientists have added another species to the list of birds that use sounds made with their feathers to communicate.

The male fork-tailed flycatcher, a passerine bird species native to the American tropics, creates unique sounds by fluttering its feathers at high frequencies, according to research published Wednesday in the journal Integrative and Comparative Biology.

“Back in the 1960’s, scientists noticed that they produce a distinctive sound only during a particular flight display,” researcher Christopher Clark, told UPI in an email.

“And those species of flycatcher in the genus Tyrannus, those that make the most distinctive sounds have the most distinctly shaped outer primary feathers,” said Clark, an associate professor of evolutionary biology at the University of California Riverside.

For the latest research, scientists conducted field studies to better understand both the mechanics of the feather fluttering and its communicative utility.

“We found that the birds don’t produce sounds every time they fly, but only under specific behavioral contexts,” lead study author Valentina Gomez told UPI in an email.

“One is during the pre-dawn display, after waking up. They begin displaying by singing and then they include feather songs. They also produce these sounds during territorial displays,” said Gomez, a doctoral student at the University of Illinois at Chicago.

To study the fluttering’s acoustic qualities, scientists captured males with mist netting, and used cameras and microphones to record the sounds the birds made as they escaped and retreated.

Fork-tailed flycatchers are quite territorial and aggressively defend their nests. Males are especially aggressive, regularly engaging in aerial battles with other males over mating opportunities and territory. They’re also more than willing to attack larger birds that stray too close to their nests.

Researchers used a taxidermy hawk outfitted with microphones and a camera to measure the movement of the fork-tailed flycatcher’s feathers during displays of aggression. The recordings revealed a difference in the sounds made by two subspecies, one that migrates long distances and another that is more stationary.

“Differences in migration likely influenced the shape of feathers and this affects the frequency at which they flutter,” Gomez said.

In effect, the two subspecies have developed dialects. Researchers suspect this phenomenon might help drive speciation, or species divergence.

“The evolution of different movement behaviors promotes the initial trigger of the speciation process,” Gomez said. “Through time, correlated evolution of morphological traits affects how they communicate.”

In other words, the difference in sound-making didn’t jumpstart the speciation process, but Gomez and her research partners hypothesize that the development of feather-flapping dialects works to reinforce the divergence.

Similarly, while the sound-making feathers of fork-tailed flycatchers may have initially evolved in response to pressures unrelated to communication, researchers claim the birds now utilize their sound-making abilities with intentionality. They’ve harnessed the power of their fluttering features for the purposes of communication.

“The birds alter how they are flapping their wings when they produce sound; their wingbeat frequency goes up by quite a bit,” Clark said. “The altered kinematics is another clue that this is ‘intentional.'”

While non-vocal communication has been observed in a variety of bird genus and species, scientists suspect the prevalence of the practice is underestimated.

Researchers hope that future investigations of feather-based communication among flycatchers will offer new insights into why so many birds have evolved non-vocal communication over and over again.

While the latest findings suggest the fork-tailed flycatcher relies on feather-based communication for pair bonding and displays of aggression, many questions about the fluttering’s utility remain.

“We still need to learn a lot about bird acoustic perception,” Gomez said.



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Once exposed to humans, animals start to lose their fear of predators

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Sept. 22 (UPI) — New research suggests animals begin to lose their fear of predators once they start encountering humans on a regular basis.

For the study, scientists surveyed the findings of 173 peer-reviewed papers on predator avoidance behaviors and traits deployed by 102 species of domesticated, captive and urbanized mammals, birds, reptiles, fish and mollusks.

The analysis, published Tuesday in the journal PLOS Biology, showed predator avoidance traits and behaviors, including vigilance, freezing and fleeing, decreased as a result of exposure to humans.

Researchers found individual variation in anti-predator characteristics increased upon a species’ initial exposure to humans, but then gradually decreased after generations of human exposure.

“While it is well known that the fact of being protected by humans decreases anti-predator capacities in animals, we did not know how fast this occurs and to what extent this is comparable between contexts,” lead researcher Benjamin Geffroy, biologist at the University of Montpellier in France, said in a news release.

The findings suggest behavioral flexibility allows for the initial increase in the variability of anti-predator traits, but researchers suspect genetic changes solidify declines in predator avoidance as subsequent generations adjust to the presence of humans.

In the studies analyzed by Geffroy and his colleagues, domesticated animals lose their anti-predator traits much more quickly than urbanized animals, which can cause problems when domesticated or urbanized species are released back into the wild.

“We also integrated physiological traits in the study but they were much less numerous that behavioral traits,” Geffroy said. “We believe they should be systematically investigated to draw a global pattern of what is happening at the individual level.

“We need more data to understand whether this occurs also with the mere presence of tourists,” Geffroy said.



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Search and rescue dogs fared well after work at 9/11 sites, study says

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Search and rescue dogs used during the 9/11 attacks lived as long as dogs not at the World Trade Center in New York City and the Pentagon, a new study finds.

“I was at Ground Zero and I would hear people make comments like, ‘Did you hear that half of the dogs that responded to the bombing in Oklahoma City died of X, Y, or Z?’ Or they’d say dogs responding to 9/11 had died,” said Dr. Cynthia Otto, director of the University of Pennsylvania’s Working Dog Center, in Philadelphia. “It was really disconcerting.”

Otto and her School of Veterinary Medicine colleagues’ findings are reassuring.

Dogs that participated in search-and-rescue efforts after 9/11 lived as long as search-and-rescue dogs not at the scene — a median of about 12.8 years, meaning half died sooner, half did not. They also outlived the life spans of their breed. There was no difference in the dogs’ cause of death.

“Honestly, this was not what we expected it’s surprising and wonderful,” said Otto, a veterinarian.

The researchers expected to see respiratory problems in the exposed dogs, but they did not. The most common cause of death was age-related conditions, such as arthritis and cancer.

For the study, Otto collected data on 95 dogs that had worked at the World Trade Center, the nearby Fresh Kills Landfill in Staten Island, N.Y., or Pentagon disaster sites in Washington, D.C. They compared these dogs with 55 search-and-rescue dogs that were not deployed on 9/11.

“We anticipated that the dogs would be the ‘canary in the coal mine’ for the human first responders since dogs age faster than humans and didn’t have any of the protective equipment during the response,” Otto said in a university news release. “But we didn’t see a lot that was concerning.”

Generally, these dogs are stronger and healthier than pets, which might partly explain why the dogs fared well, she said.

The findings were published Sept. 21 in the Journal of the American Veterinary Medical Association.

More information

For more on responder health after 9/11, visit the New York State Department of Health.

Copyright 2020 HealthDay. All rights reserved.



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