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Smallest, densest white dwarf ever discovered packs the sun's mass into a moon-size stellar corpse – Space.com

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Astronomers may have discovered the smallest and heaviest white dwarf star ever seen, a smoldering ember about the size of our moon but 450,000 times more massive than Earth, a new study finds.

White dwarfs are usually about the size of Earth and are the cool, dim cores of dead stars that are left behind after average-size stars have exhausted their fuel and shed their outer layers. Our sun will one day become a white dwarf, as will about 97% of all stars.

Although the sun is alone in space without a stellar partner, many stars orbit around each other in pairs. If these binary stars are both less than eight times the mass of the sun, they will both evolve into white dwarfs over time.

Related: Oddball giant white dwarf may have formed in epic crash of smaller stars

The newfound white dwarf, designated ZTF J1901+1458, is located about 130 light-years from Earth and may be an example of what can happen when white dwarf pairs merge. If the white dwarfs were more massive, they would explode in a powerful thermonuclear explosion known as a Type Ia supernova. However, if their combined masses fell below a certain threshold, they could form a new white dwarf heavier than either of its parents, which is what scientists think happened in the case of ZTF J1901+1458.

“Our discovery is the most massive and smallest white dwarf ever found,” study lead author Ilaria Caiazzo, an astrophysicist at the California Institute of Technology in Pasadena, told Space.com.

The discovery was made using the Zwicky Transient Facility at the Palomar Observatory in California, which scans the entire northern sky every two nights looking for cosmic bodies that blink, erupt, move or similarly change in brightness. Study co-author Kevin Burdge, an astrophysicist at the California Institute of Technology in Pasadena, first spotted the new white dwarf based on its high mass and rapid spin.

The researchers used a host of telescopes to help analyze the dead star, which is about 100 million years old or less. These included the Hale Telescope at Palomar, the W.M. Keck Observatory‘s Keck I telescope, the European Gaia space observatory, the University of Hawaii’s Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) and NASA’s Neil Gehrels Swift Observatory.

The scientists found the white dwarf was about 2,670 miles (4,300 kilometers) wide, making it a bit larger than the moon, which is about 2,158 miles (3,474 km) in diameter. ZTF J1901+1458’s tiny size makes it the smallest known white dwarf, edging out previous record holders, RE J0317-853 and WD 1832+089, which each have diameters of about 3,100 miles (5,000 km).

At the same time, the newfound white dwarf is about 1.35 times the mass of our sun, which may make it the most massive white dwarf discovered yet.

Related: What makes this low-mass white dwarf so ‘impossible’ to behold?

“It might be a bit counter-intuitive that the most massive white dwarf known is also the smallest white dwarf found,” Caiazzo said. This is because gravity and other factors lead white dwarfs to be smaller the more massive they are, she added.

This white dwarf is barely under the mass at which one would expect a white dwarf to detonate. “This one is really at the limit,” Caiazzo said. “If it was slightly more massive, it would have exploded.”

The white dwarf spins very rapidly, completing one revolution every seven minutes. When its progenitor stars spiraled together to merge, ZTF J1901+1458 inherited their combined spin, the researchers said. (The fastest-whirling white dwarf known, called EPIC 228939929, rotates every 5.3 minutes).

The white dwarf’s quick rate of spin also helps give it a very powerful magnetic field, more than one billion times stronger than Earth’s. “All of these characteristics — its mass and spin and high magnetic field — all suggest this white dwarf was not born the same as normal white dwarfs,” Caiazzo said.

Since this white dwarf is so massive, it may be possible that it might collapse further, as the incredible pressure within its core forces electrons to fuse with protons in atomic nuclei to form neutrons. “It could get even smaller than the moon,” Caiazzo said, perhaps shrinking as small as about 1,240 to 1,865 miles (2000 to 3000 km) wide.

If this shrinking does occur, at some point maybe 100 million to 200 million years from now, the white dwarf might become unstable and detonate as a thermonuclear type Ia supernova, Caiazzo said. Another possibility is that if a large enough number of electrons get captured, the white dwarf might potentially collapse to form a neutron-rich dead star known as a neutron star.

“A neutron star is an extremely dense object the mass of the sun but just the size of a city, so even more extreme than this white dwarf,” Caiazzo said.

If a white dwarf does collapse to form a neutron star, atoms fusing together within its core would release a huge amount of heat, potentially in just hours or days. “The entire white dwarf would very quickly burn,” Caiazzo said.

Neutron stars are thought to normally form when stars much more massive than our sun explode as supernovas, Caiazzo explained. If giant white dwarfs can also collapse to become neutron stars, a significant number of neutron stars may arise this way. However, if a white dwarf’s core freezes to become a crystalline solid faster than it shrinks, this collapse will likely not happen.

“We don’t know if such a collapse may happen, and if it does, which outcomes might occur,” Caiazzo said. “But if white dwarfs can create neutron stars, this could be a quite common way to form neutron stars.”

In the future, the scientists hope to use the Zwicky Transient Facility to find more white dwarfs like this one and to analyze white dwarfs as a whole. 

“There are so many questions to address, such as what is the rate of white dwarf mergers in the galaxy, and is it enough to explain the number of type Ia supernovae?” Caiazzo said in a statement. “How is a magnetic field generated in these powerful events, and why is there such diversity in magnetic field strengths among white dwarfs? Finding a large population of white dwarfs born from mergers will help us answer all these questions and more.”

The scientists detailed their findings online June 30 in the journal Nature.

Follow us on Twitter @Spacedotcom and on Facebook. 

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Climate tipping points are difficult to predict. In Canada and beyond, they might have already arrived – CBC.ca

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Scientists have been watching extreme weather events unfold all over the world this summer, seeing the many links between heatwaves, floods, droughts and climate change. 

But the scale of some of these events, and just how dramatically they have upended previous records, suggests that the climate is no longer changing in a gradual, predictable way.

Deadly heat waves and other wild weather are putting renewed attention on tipping points  — the idea that major shifts to key ecosystems, such as Greenland’s ice sheets or the Amazon rainforest, can cause large, irreversible changes to the planet’s climate balance. 

“Tipping points are large-scale changes that could happen abruptly and could be potentially irreversible,” said Owen Gaffney, an analyst at the Stockholm Resilience Centre, a research institute

WATCH | Smog warnings might become the norm. How do we protect ourselves?

Hashem Akbari, an environmental engineer at Concordia University, says the solution must include stopping climate change. 5:23

He co-authored a 2019 article in the journal Nature that listed nine tipping points around the world that scientists are watching with growing concern. A prime example is the ice-sheets in parts of Antarctica and Greenland. Rather than gradually shrinking as the climate warms, research suggests the sheets could hit points of no return leading to rapid and irreversible ice loss  — and a corresponding rise in global sea levels.

In Greenland, models suggest the “ice sheet could be doomed at 1.5 C of warming, which could happen as soon as 2030,” the report said.

In Canada, the trends are worrying. This summer, various parts of British Columbia saw temperature records broken during the heatwave in June, notably the town of Lytton, which set the record for the hottest temperature ever recorded in Canada at 49.6 C — a remarkable 5.2 C increase over Lytton’s previous heat record (which was also a record for B.C.) in 1941.

Lytton, B.C., set Canada’s hottest temperature record this summer, and was mostly destroyed by a wildfire afterwards. The new record was about five degrees above the town’s previous record. (Darryl Dyck/The Canadian Press)

“The analogy that scientists used to use is that as you warm the climate, it is like loading a pair of dice. And so now when you roll the dice, you get more sixes than you would have before,” said Simon Donner, a professor at the University of British Columbia who studies climate science and public policy. 

“But what we’ve been seeing this summer isn’t a six, it’s like a seven or eight, something that wasn’t possible with the old dice.”

Simon Donner is a climate science and public policy researcher at the University of British Columbia. (Don Erhardt)

A study examining how much of the heatwave on the west coast could be attributed to human-caused climate change by a group of international scientists suggested that one explanation for the high temperatures could be “​​nonlinear interactions in the climate.”

Rather than gradual increases in temperature extremes, this theory suggests that the present amount of climate change is causing bigger-than-expected increases in extreme heat due to interactions in the climate system that are not fully understood.

And that raises questions about what cities and communities need to do to adapt to a future climate that looks increasingly uncertain. 

Tipping points may have been already reached

An international group of climate scientists are now warning that there is “mounting evidence that we are nearing or have already crossed tipping points associated with critical parts of the Earth system.” In a paper published in the journal BioScience on July 28, researchers pointed to the West Antarctic and Greenland ice sheets, warm-water coral reefs, and the Amazon rainforest as climate systems that were possibly nearing or had already reached their tipping point.

The paper tracked 31 key climate variables, such as global emissions and tree cover loss and found that 18 are at all-time records. That includes the three important greenhouse gases, carbon dioxide, methane and nitrous oxide, which reached new records for atmospheric concentrations in both 2020 and 2021.

Given the impacts we are seeing at roughly 1.25 C of global warming, “combined with the many reinforcing feedback loops and potential tipping points, massive-scale climate action is urgently needed,” the paper said.

Trucks carry relief supplies in central China’s Henan Province, hit by flooding in July due to unprecedented rain. Climate change will make floods more severe in many parts of the world. (Dake Kang/The Associated Press)

Paul Ritchie, a mathematician and climate scientist at the University of Exeter in the U.K., researches where those tipping points lie and how far we can overshoot some of them while still being able to recover. Certain changes, such as the loss of ice sheets, have a relatively long timescale, Ritchie said, occurring over many centuries.

“But then there are these other elements… where these can happen over much shorter timescales, maybe years or decades,” he said. 

“So pretty much as soon as we go over these particular thresholds, we might instantly know because we have this sudden loss of the Amazon rainforest or the monsoon suddenly stops operating.”

Both events would have devastating consequences. Millions of people rely on the monsoons for agriculture, while the Amazon’s loss could release even more carbon and accelerate global warming.

Adaptation still possible, but Canada not there yet

Canada announced a plan to develop a national adaptation strategy in December 2020. But experts warn the country is not ready for the climate we have now, and needs to move fast to respond to the future.

“The reality is that we should assume that we’re not going to meet that [Paris Agreement] target of 2 C,” said Gordon McBean, a professor at the Western University in London, Ont., of the global deal to reduce carbon emissions to stop the worst impacts of climate change. 

McBean was the lead investigator on a report for the federal government earlier this year on building community resilience to climate change.

His report found that while many cities have high level plans to address climate change, others still lack detailed implementation strategies or funding. 

“Most actions to build community resilience in Canada are unplanned and take place in recovery following an extreme loss event,” the report said.

Government workers check an area consumed by fire in the Amazon rainforest in Brazil in 2020. The Amazon is one system that could be nearing a tipping point. (Andre Penner/The Associated Press)

As average temperatures rise in linearly fashion, the number of extreme weather events increases more dramatically, McBean said. “An adaptation strategy has to take into account not just future projections of weather, but also future projections of greenhouse gas emissions, and the chance that the rest of the world will not meet its emissions reduction goals.”

Recent heat domes and tornados are examples of the kinds of events that will happen more often in the future, he said.

With the climate set to continue to change for years to come, and new information coming out about the dangers of tipping points that could lead to extreme weather that’s unforeseen, adaptation has become more urgent.

McBean said there’s enough information available now to start planning for that uncertain future, and make communities more resilient.

“It’s not saying we failed. It’s saying here’s what we need to do,” he said.

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It's not just the smoke — as climate change prompts more wildfires, hidden health risks emerge – CBC.ca

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For 53-year-old photographer Stefanie Harron, the past few weeks have felt like living in a smoky, fiery hell. 

The air in her hometown of Castlegar, B.C., has been thick with smoke as wildfires rage nearby. Her neighbour’s house is barely visible though a mere 25 metres away. Her eyes water and her asthma and chronic obstructive pulmonary disease (COPD) make the simple act of breathing a challenge. 

Instead of using her puffer once or twice a week, she’s now using it four to five times a day. 

“The air, thick with particulates, makes me want to vomit,” she says. “The first thing you notice is the taste before the acrid smell. I would compare it to living in an ashtray. Every breath without a respirator is like short gasps for air,” Harron says. “[I’m] almost scared to take a deep breath knowing it will result in coughing and make it worse and more difficult.”

Harron is not alone. As roughly 250 fires rage across the province, tens of thousands of people have been exposed to poor air quality, and it’s particularly difficult on those who have health issues. Another 200 wildfires burn across the country.

Climate change is expected to exacerbate wildfires, with estimates of anywhere from a 74 to 118 per cent increase in Canadian land burned by 2100

WATCH | What’s the health impact of wildfire smoke?

Wildfire season in Canada contributes to increases in emergency room visits and for some people with respiratory illnesses, it can lead to severe outcomes. 4:32

And though the risks from smoke are among the biggest worries, there are also less-obvious health concerns such as the impact on mental health and clean water to consider.

Questions about long-term effects

Scientists examining air pollution — including that produced by wildfires — study various types of emissions, but among those most commonly measured is particulate matter (PM), specifically PM 2.5. 

PM 2.5 are fine particles measuring roughly 2.5 micrometres and smaller. Inhaling them can affect the lungs and heart, and are of serious concern to those with existing health issues such as asthma or heart and lung disease.

This illustration shows the approximate size of various particles. (Environmental Protection Agency)

The immediate effects may be obvious, but doctors are also trying to better understand the long-term impact.

“Four of the past five summers in British Columbia have had significant wildfire smoke events. And … we’re not really sure what the long-term health consequences are for populations who are exposed this way, sort of season after season,” said Sarah Henderson, the scientific director of environmental health at the British Columbia Centre for Disease Control. “There’s the potential for these big and significant wildfire smoke exposures to affect the health of those individuals throughout their lives.”

And those particles aren’t just concerning for those who live near the fires. Smoke can travel far from its source, sometimes traversing the globe. 

“For major smoke events, you’ll see the intercontinental transport of smoke,” said Jeff Eyamie, regional air health officer for Health Canada. “For the Fort Mac fires [in 2016], they had smoke as far away as the Ukraine that they could trace back to the Fort McMurray fires.” 

Here at home, on July 19, Environment and Climate Change Canada issued an air quality advisory for southern Ontario, including Toronto, as well as Ottawa as smoke from wildfires in northwestern Ontario blanketed the province. A week later, parts of Quebec, including Montreal, were put under a similar advisory.

Anxious and irritable

And then there is the impact on mental health. Wildfires sometimes force people to be evacuated from their homes, causing high levels of stress. Those who live in areas where the air is thick with smoke may also be forced to remain indoors for long periods of time. In addition, there may be other hidden costs, like a run on asthma medication.

An orange sun is seen in the sky at Tyendinaga Mohawk Territory, roughly 12 kilometres southwest of Napanee, Ont. (Submitted by Malcolm Park)

Dr. Courtney Howard, an emergency physician in Yellowknife and past president of the Canadian Association of Physicians for the Environment, was involved in a study that interviewed 30 residents in Yellowknife, which experiences wildfires every year. In the study, they were asked what it felt like to live through a long period of smoky air. 

“What people told us was that they felt anxious and irritable,” she said. “They were cooped up, had that cabin fever … lots of comments about the decrease in physical activity. And so, of course, what that means is that people lose the treatment benefit that we know we get from being outside in nature, exercising.” 

At one point, the mayor of Yellowknife opened up an indoor exercise space so people could be active in a well-ventilated area, said Howard. It’s something she believes officials might need to consider in a future with climate change.

Impact on the environment

The particles that waft into the air affect more than just physical health. Those particles also land on trees, plants, buildings and end up in water.

Ash, sediment and minerals not only flow into streams and rivers, but also downstream into lakes and reservoirs, potentially affecting drinking water and contributing to algal blooms.

The good news is that in Canada the water purification systems are able to filter them out for the most part. But the added strain on the system means that it may cost more to handle the higher level of contaminants. 

“The issue around fire and drinking water is not — and I have to emphasize not — generally an issue of ‘Am I drinking something with some sort of toxic contaminant in it?'” says Monica Emelko, a professor in the University of Waterloo’s civil and environmental engineering department. “It’s rather an issue of: ‘If toxic contaminants get into the water, will you be able to have something running out of your tap that you can use?’ … When we have these disturbances on the landscape, that really pushes our ability to do that in a cost effective way.”

There are also effects on ecosystems, says Uldis Silins, a professor of forest hydrology at the University of Alberta. For example, as sediment and minerals flow into water they can upset the chemical balance in a lake. 

“One of the things that we’ve seen repetitively is very large impacts on things like sediment,” Silins said. “Unlike other kinds of disturbance pressures we might be thinking about, the scope of those impacts was not a 30 or 50 per cent kind of increase in sediment production, they were hundreds of percentages or thousands of percentages, so, orders of magnitude increases in those contaminants.” 

And as humans rely on those ecosystems, there may be other consequences – such as the impact on fish in lakes that are eaten. 

“I don’t think it’s bold of me to say we’re in a climate emergency. And everyone needs to be aware that this is happening,” said Health Canada’s Eyamie. “The models may not be 100 per cent accurate, but they’ll be accurate enough that this should be cause for concern for everyone.”

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Russian lab module docks with space station after 8-day trip – St. Albert Today

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MOSCOW — A newly arrived Russian science lab briefly knocked the International Space Station out of position Thursday when it accidentally fired its thrusters.

For 47 minutes, the space station lost control of its orientation when the firing occurred a few hours after docking, pushing the orbiting complex from its normal configuration. The station’s position is key for getting power from solar panels and or communications. Communications with ground controllers also blipped out twice for a few minutes.

Flight controllers regained control using thrusters on other Russian components at the station to right the ship, and it is now stable and safe, NASA said.

“We haven’t noticed any damage,” space station program manager Joel Montalbano said in a late afternoon press conference. “There was no immediate danger at anytime to the crew.”

Montalbano said the crew didn’t really feel any movement or any shaking. NASA said the station moved 45 degrees out of attitude, about one-eighth of a complete circle. The complex was never spinning, NASA spokesman Bob Jacobs said.

NASA’s human spaceflight chief Kathy Lueders called it “a pretty exciting hour.”

The incident caused NASA to postpone a repeat test flight for Boeing’s crew capsule that had been set for Friday afternoon from Florida. It will be Boeing’s second attempt to reach the 250-mile-high station before putting astronauts on board; software problems botched the first test.

Russia’s long-delayed 22-ton (20-metric-ton) lab called Nauka arrived earlier Thursday, eight days after it launched from the Russian launch facility in Baikonur, Kazakhstan.

The launch of Nauka, which will provide more room for scientific experiments and space for the crew, had been repeatedly delayed because of technical problems. It was initially scheduled to go up in 2007.

In 2013, experts found contamination in its fuel system, resulting in a long and costly replacement. Other Nauka systems also underwent modernization or repairs.

Stretching 43 feet (13 meters) long, Nauka became the first new compartment for the Russian segment of the outpost since 2010. On Monday, one of the older Russian units, the Pirs spacewalking compartment, undocked from the station to free up room for the new lab.

Nauka will require many maneuvers, including up to 11 spacewalks beginning in early September, to prepare it for operation.

The space station is currently operated by NASA astronauts Mark Vande Hei, Shane Kimbrough and Megan McArthur; Oleg Novitsky and Pyotr Dubrov of Russia’s Roscosmos space corporation; Japan Aerospace Exploration Agency astronaut Akihiko Hoshide and European Space Agency astronaut Thomas Pesquet.

In 1998, Russia launched the station’s first compartment, Zarya, which was followed in 2000 by another big piece, Zvezda, and three smaller modules in the following years. The last of them, Rassvet, arrived at the station in 2010.

Russian space officials downplayed the incident with Dmitry Rogozin, head of Roscosmos, tweeting: “All in order at the ISS. The crew is resting, which is what I advise you to do as well.”

Seth Borenstein, The Associated Press




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