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'Oumuamua could be a relic from giant clouds where stars are born – CBC.ca

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When the mysterious object ‘Oumuamua zoomed through our solar system back in 2017, it was clear it was unlike any interstellar object astronomers had ever seen.

It was strangely shaped. It wasn’t an asteroid. It seemed to behave like a comet — it changed speed as it flew around the sun like comets do. But it had no signature cometary tail. It was a cosmic mystery with no good answer, until now. 

In a new study, scientists suggest what they describe as the most likely explanation for all of its oddities. They think ‘Oumuamua is a dense chunk of exotic hydrogen ice mixed with a little dust. 

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“If we’re right and ‘Oumuamua is a cosmic hydrogen iceberg, that’s fundamentally a new type of astrophysical object,” said Darryl Seligman, a postdoctoral fellow at the University of Chicago.

Hydrogen ice forms at spectacularly low temperatures, only six degrees above absolute zero. 

“The only places you could even feasibly form solid macroscopic hydrogen icebergs are in the coldest, densest, and darkest parts of the galaxy. And those are the giant molecular cloud cores.”

In our Milky Way galaxy, there are clouds of gas and dust that form molecular clouds. Among the most famous are the so -called “Pillars of Creation” seen in images captured by the Hubble Space Telescope. Light doesn’t penetrate inside these clouds, so hydrogen — which normally exists in a gaseous state — freezes into dense pre-stellar cores. In many of these molecular clouds, these become the building blocks of new stars. But this isn’t the fate of all of them.

“What you do is you take a starless core that fails to form a star, you build up these large macroscopic hydrogen icebergs and eventually the cloud disperses and these things are just gently released into the galaxy,” Seligman told Quirks & Quarks‘ Bob McDonald. 

The famous Pillars of Creation are an example of the type of molecular clouds that function as stellar nurseries and could give rise to hydrogen icebergs like ‘Oumuamua. (NASA, ESA, and the Hubble Heritage Team [STScI/AURA])

Parsing out clues from ‘Oumuamua’s behaviour

The starting point for Seligman in solving this mystery was a study describing how the sun’s gravitational acceleration couldn’t explain ‘Oumuamua’s trajectory. 

“There was an extra force that was acting on ‘Oumuamua and always pushing it away from the sun,” he explained.

The sun’s energy provides that extra force by heating up the ice, turning it into gas that explodes toward the sun pushing ‘Oumuamua in the opposite direction. 

Seligman and his supervisor asked themselves: “What species of ice could have powered the non-gravitational acceleration of ‘Oumuamua just from the amount of energy ‘Oumuamua received from the sun?”

There’s probably about one passing through the inner solar system at any given time.– Darryl Seligman, University of Chicago

“The constraint is shockingly powerful,” said Seligman. “Almost nothing works.”

Ordinary comets are mostly made of water ice, but their calculations showed that wouldn’t provide enough thrust to explain the observations. Their next possibility was hydrogen ice. 

“Based on the fact that hydrogen ice is not very well held together, that seems like one of the only possible — and certainly the most likely accelerant,” he said.

Hydrogen icebergs in our solar system likely extremely common

It’s entirely possible objects like ‘Oumuamua have been visiting our solar system in some numbers, but we’ve never seen them.

Seligman said ‘Oumuamua was very small and dim when scientists first spotted it quite close to Earth — about 40 lunar distances away. And the telescope that discovered it has only been in operation since 2010. 

“The fact that we saw one of those in the last couple of years when Pan-STARRS, which is the survey in Hawaii that detected ‘Oumuamua was operating, means that there’s probably about one passing through the inner solar system at any given time,” he said.

In a previous study, he showed that when the Vera Rubin Observatory comes online, we should be able to detect a lot more of these hydrogen icebergs sooner than we observed ‘Oumuamua.

The Vera Rubin Observatory is expected to become operational later this year. (LSST Project/NSF/AURA)

Given the effort we put into studying comets, asteroids and meteorites to learn about the early formation of our solar system, Seligman said hydrogen icebergs will give us an even earlier glimpse into the conditions that give rise to stars. 

“If the giant molecular cloud cores — the sites of star formation — are locking up their material into solid hydrogen icebergs, and they’re making so many of them that they’re passing through our solar system all the time, that means that we could up close study the most pristine and primordial material imaginable in the galaxy,” he said.

Produced and written by Sonya Buyting

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SpaceX launch marks 300th successful booster landing – Phys.org

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Credit: Unsplash/CC0 Public Domain

SpaceX sent up the 30th launch from the Space Coast for the year on the evening of April 23, a mission that also featured the company’s 300th successful booster recovery.

A Falcon 9 rocket carrying 23 of SpaceX’s Starlink internet satellites blasted off at 6:17 p.m. Eastern time from Cape Canaveral Space Force Station’s Space Launch Complex 40.

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The first-stage booster set a milestone of the 300th time a Falcon 9 or Falcon Heavy booster made a successful recovery landing, and the 270th time SpaceX has reflown a booster.

This particular booster made its ninth trip to space, a resume that includes one human spaceflight, Crew-6. It made its latest recovery landing downrange on the droneship Just Read the Instructions in the Atlantic Ocean.

The company’s first successful booster recovery came in December 2015, and it has not had a failed booster landing since February 2021.

The current record holder for flights flew 11 days ago making its 20th trip off the .

SpaceX has been responsible for all but two of the launches this year from either Kennedy Space Center or Cape Canaveral with United Launch Alliance having launched the other two.

SpaceX could knock out more launches before the end of the month, putting the Space Coast on pace to hit more than 90 by the end of the year, but the rate of launches by SpaceX is also set to pick up for the remainder of the year with some turnaround times at the Cape’s SLC-40 coming in less than three days.

That could amp up frequency so the Space Coast could surpass 100 launches before the end of the year, with the majority coming from SpaceX. It hosted 72 launches in 2023.

More launches from ULA are on tap as well, though, including the May 6 launch atop an Atlas V rocket of the Boeing CST-100 Starliner with a pair of NASA astronauts to the International Space Station.

ULA is also preparing for the second launch ever of its new Vulcan Centaur rocket, which recently received its second Blue Origin BE-4 engine and is just waiting on the payload, Sierra Space’s Dream Chaser spacecraft, to make its way to the Space Coast.

Blue Origin has its own it wants to launch this year as well, with New Glenn making its debut as early as September, according to SLD 45’s range manifest.

2024 Orlando Sentinel. Distributed by Tribune Content Agency, LLC.

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SpaceX launch marks 300th successful booster landing (2024, April 24)
retrieved 24 April 2024
from https://phys.org/news/2024-04-spacex-300th-successful-booster.html

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Wildlife Wednesday: loons are suffering as water clarity diminishes – Canadian Geographic

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The common loon, that icon of northern wilderness, is under threat from climate change due to declining water clarity. Published earlier this month in the journal Ecology, a study conducted by biologists from Chapman University and Rensselaer Polytechnic Institute in the U.S. has demonstrated the first clear evidence of an effect of climate change on this species whose distinct call is so tied to the soundscape of Canada’s lakes and wetlands.

Through the course of their research, the scientists found that July rainfall results in reduced July water clarify in loon territories in Northern Wisconsin. In turn, this makes it difficult for adult loons to find and capture their prey — mainly small fish — underwater, meaning they are unable to meet their chicks’ metabolic needs. Undernourished, the chicks face higher mortality rates. The consistent foraging techniques used by loons across their range means this impact is likely echoed wherever they are found — from Alaska to Canada to Iceland.

The researchers used Landsat imagery to find that there has been a 25-year consistent decline in water clarity, and during this period, body weights of adult loon and chicks alike have also declined. With July being the month of most rapid growth in young loons, the study also pinpointed water clarity in July as being the greatest predictor of loon body weight. 

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One explanation for why heavier rainfall leads to reduced water clarity is the rain might carry dissolved organic matter into lakes from adjacent streams and shoreline areas. Lawn fertilizers, pet waste and septic system leaks may also be to blame.

The researchers, led by Chapman University professor Walter Piper, hope to use these insights to further conservation efforts for this bird Piper describes as both “so beloved and so poorly understood.”

Return of the king

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Giant prehistoric salmon had tusk-like teeth for defence, building nests

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The artwork and publicity materials showcasing a giant salmon that lived five million years ago were ready to go to promote a new exhibit, when the discovery of two fossilized skulls immediately changed what researchers knew about the fish.

Initial fossil discoveries of the 2.7-metre-long salmon in Oregon in the 1970s were incomplete and had led researchers to mistakenly suggest the fish had fang-like teeth.

It was dubbed the “sabre-toothed salmon” and became a kind of mascot for the Museum of Natural and Cultural History at the University of Oregon, says researcher Edward Davis.

But then came discovery of two skulls in 2014.

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Davis, a member of the team that found the skulls, says it wasn’t until they got back to the lab that he realized the significance of the discovery that has led to the renaming of the fish in a new, peer-reviewed study.

“There were these two skulls staring at me with sideways teeth,” says Davis, an associate professor in the department of earth sciences at the university.

In that position, the tusk-like teeth could not have been used for biting, he says.

“That was definitely a surprising moment,” says Davis, who serves as director of the Condon Fossil Collection at the university’s Museum of Natural and Cultural History.

“I realized that all of the artwork and all of the publicity materials and bumper stickers and buttons and T-shirts we had just made two months prior, for the new exhibit, were all out of date,” he says with a laugh.

Davis is co-author of the new study in the journal PLOS One, which renames the giant fish the “spike-toothed salmon.”

It says the salmon used the tusk-like spikes for building nests to spawn, and as defence mechanisms against predators and other salmon.

The salmon lived about five million years ago at a time when Earth was transitioning from warmer to relatively cooler conditions, Davis says.

It’s hard to know exactly why the relatives of today’s sockeye went extinct, but Davis says the cooler conditions would have affected the productivity of the Pacific Ocean and the amount of rain feeding rivers that served as their spawning areas.

Another co-author, Brian Sidlauskas, says a fish the size of the spike-toothed salmon must have been targeted by predators such as killer whales or sharks.

“I like to think … it’s almost like a sledgehammer, these salmon swinging their head back and forth in order to fend off things that might want to feast on them,” he says.

Sidlauskas says analysis by the lead author of the paper, Kerin Claeson, found both male and female salmon had the “multi-functional” spike-tooth feature.

“That’s part of our reason for hypothesizing that this tooth is multi-functional … It could easily be for digging out nests,” he says.

“Think about how big the (nest) would have to be for an animal of this size, and then carving it out in what’s probably pretty shallow water; and so having an extra digging tool attached to your head could be really useful.”

Sidlauskas says the giant salmon help researchers understand the boundaries of what’s possible with the evolution of salmon, but they also capture the human imagination and a sense of wonder about what’s possible on Earth.

“I think it helps us value a little more what we do still have, or I hope that it does. That animal is no longer with us, but it is a product of the same biosphere that sustains us.”

This report by The Canadian Press was first published April 24, 2024.

Brenna Owen, The Canadian Press

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