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How Do Stars Get So Massive? Their Dense, Unstable Disks Could Be To Blame

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Gaia 17bpi star

This artist’s impression shows the inner disk of a young star collapsing onto its host, becoming hot enough to emit visible light. (Credit: Caltech/T. Pyle (IPAC))

Any bodybuilder will tell you that you can’t bulk up overnight, but that might not be true for stars. While observing infant star Gaia 17bpi, astronomers saw part of its dense disk collapse onto its body below — adding mass at an incredible rate. This encounter is one of the few times that researchers have seen a star’s disk become gravitationally unstable and fall down to its host. The findings, which will appear in the Astrophysical Journal, could shed light on stellar evolution and help answer the ever-looming question: how do stars become so massive?

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Astronomers have a pretty solid understanding of star formation and evolution: a cold, dense cloud of dust and gas collapses under its own gravity and condenses into a hot ball of matter. The remaining dust and gas form a swirling disk around the infant star, from which it slowly but continually steals material from. Previous observations, though, show that the rate stars steal from their disks is too slow to result in their final, enormous masses.

Luckily, one classification of stars could help explain how they gain their mysterious, unaccounted mass. Called FU Ori’s, this class represents stars that are only a few million years old and are surrounded by thick disks of dust and gas. As these disks grow, they become so massive that they lose gravitational stability, and end up dumping their heavy, dusty loads onto their host stars. It’s believed that all stars undergo 10 to 20 of these FU Ori events in their early years, but since they’re still hidden behind the molecular clouds that they formed in, they can be difficult to detect.

Tracking Trio

But thanks to data from three high-tech instruments, a team led by California Institute of Technology (Caltech) astronomers was able to capture one of these rare events. The discovery started when ESA’s Gaia mission, which is tasked with mapping a billion nearby stars, spotted a star that was increasing in brightness. Intrigued, the team followed up and found that NASA’s NEOWISE satellite, which scans the skies for asteroids and comets, and their Spitzer Space Telescope witnessed the event, too.

Capable to detecting infrared wavelengths, data from both NEOWISE and Spitzer showed that dust and gas in the star’s disk started to build up and become hotter, causing it to emit beams of infrared light. It’s believed that part of the disk grew so dense that it collapsed under its own gravity and fell toward its host star, dubbed Gaia 17bpi. And when it did, the matter grew hot enough to emit the influx of visible light detected by Gaia.

“These FU Ori events are extremely important in our current understanding of the process of star formation but have remained almost mythical because they have been so difficult to observe,” said Lynne Hillenbrand, a Caltech astronomy professor and lead author of the paper, in a media release. “This is actually the first time we’ve ever seen one of these events as it happens in both optical and infrared light, and these data have let us map the movement of material through the disk and onto the star.”

Added to the list of just 25 FU Ori’s ever detected, Gaia 17bpi’s sudden growth spurt could further solidify this stellar evolution theory, and help solve the mystery of massive stars once and for all.

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Ecology

Globe Climate: Canada’s resource reckoning is coming

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Good afternoon, and welcome to Globe Climate, a newsletter about climate change, environment and resources in Canada.

This afternoon, the Alberta government announced that it is restoring a coal mining policy it revoked last spring. At the time, the move provoked a widespread public backlash detailed by The Globe. The original decision, which opened up more than 1.4 million hectares to exploration, was made without public consultation. Premier Jason Kenney previously defended the changes.

Lots more on coal and Canada’s resources industry in this week’s newsletter edition.

Now, let’s catch you up on other news.

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Ecology

‘Incredibly destructive’: Canada’s Prairies to see devastating impact of climate change

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As the climate continues to warm at an alarming rate, experts warn if dramatic steps to mitigate global warming are not taken, the effects in Canada’s Prairie region will be devastating to the country’s agriculture sector.

According to Environment and Climate Change Canada, the country is warming, on average, about double the global rate.

Scientists with the National Oceanic and Atmospheric Administration in the U.S. recently found 2020 was earth’s second-hottest year on record, with the average land and ocean surface temperature across the globe at 0.98 of a degree C above the 20th-century average.

However, the agency found the northern hemisphere saw its hottest year on record, at 1.28 degrees C above the average.

“(In Canada) we are looking at about 6.4C degrees of warming this century, which isn’t much less than one degree per decade, which is just a terrifying rate of warming,” Darrin Qualman, the director of climate crisis policy and action at the National Farmer’s Union said.

Qualman said there is “massive change coming” to Canada’s Prairies, which will be “incredibly destructive.”

“It’s not going too far to say that if we made that happen, parts of the Prairies wouldn’t be farmable anymore,” he said.

According to the federal government, in 2018 Canada’s agriculture and agri-food system generated $143 billion, accounting for 7.4 per cent of the country’s GDP.

The sector employed 2.3 million people in 2018. The majority of the 64.2 million hectares of farmland in Canada is concentrated in the Prairies and in southern Ontario.

The effects of climate change are already being felt on the ground in the Prairies, Qualman said, adding that the NFU has already heard from farmers complaining of “challenging weather.”

“People are sharing pictures of flattened crops and buildings, et cetera, that have been damaged,” he said. “And we’re still at the beginning of this.”

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Ecology

Insect-based dog food aims to cut your pet’s carbon pawprint

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Meat has an enormous carbon footprint, with livestock liable for about 15 per cent of worldwide emissions, as we have beforehand mentioned on this e-newsletter. That is prompted specialists to suggest consuming much less meat for sustainability (and well being) causes.

However what about your pet? One research discovered that the methane and nitrous oxide emissions generated by canine and cat meals within the U.S. alone had been equal to about 64 million tonnes of CO2, or roughly the quantity produced by 13.6 million automobiles. And it might be getting worse, with a development towards feeding pets “human-grade” meat.

That is prompted some pet meals makers to look to lower-carbon protein sources — together with bugs.

Research present that producing insect-based meals requires far much less feed, land and water and generates far fewer greenhouse fuel emissions per kilogram than meats comparable to beef, pork or rooster.

That is one of many causes increasingly more pet meals containing insect protein are hitting the market. Purina, a model owned by multinational Nestlé, launched a line of canine and cat meals containing black soldier fly larvae in Switzerland in November.

In Canada, Montreal-based Wilder Harrier began promoting canine treats made with cricket protein in 2015 and pet food made with black soldier fly larvae in 2019. It plans to broaden to launch a line of insect-based cat treats later this yr and cat meals in 2022 due to “a ton of demand,” mentioned firm co-founder Philippe Poirier.

Wilder Harrier initially labored with animal nutritionists on insect-based merchandise to unravel a unique downside — specifically, the founders’ canines had allergy symptoms to frequent meats utilized in canine meals. Poirier mentioned now about half its prospects hunt down the product due to their pets’ allergy symptoms and about half for environmental causes.

Dr. Cailin Heinze, a U.S.-based veterinary nutritionist licensed by the American School of Veterinary Vitamin, has written concerning the environmental influence of pet meals. She mentioned we’re typically “not as involved as we probably ought to [be]” concerning the environmental footprint of pets.

Alternatively, she famous that the longer-term influence of newer diets, comparable to vegan meals and people containing bugs, hasn’t been nicely examined in comparison with conventional pet meals.

Maria Cattai de Godoy, an assistant professor of animal sciences on the College of Illinois who research novel proteins for pet meals (together with bugs, yeast and plant-based substances), mentioned such substances are rigorously examined to find out their security and diet earlier than being added to pet meals. 

“This can be a very extremely regulated trade,” she mentioned, however admitted it is also evolving.

Relating to bugs, she mentioned constructive information “reveals promise in direction of utilizing them increasingly more in pet meals.” Insect-based proteins have additionally earned the endorsement of the British Veterinary Affiliation, which says some insect-based meals could also be higher for pets than prime steak.

However Godoy famous that there isn’t any one-size-fits-all resolution, and pet homeowners ought to take into consideration the wants of their very own particular person pet and analysis whether or not a specific weight loss plan can be appropriate.

She mentioned that other than the kind of protein, issues like packaging and manufacturing strategies may also make a distinction. For instance, utilizing meat byproducts that may in any other case turn into waste would not drive elevated meat manufacturing the identical approach as utilizing human-grade meat.

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