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What The Heaviest, Smallest White Dwarf Ever Found Means For Science – Forbes



Someday, even our own Sun will eventually run out of hydrogen fuel in its core, bringing a tremendous set of changes to our Solar System. Its core will contract and heat up while its outer layers expand and slowly get expelled, signifying our transition into a red giant. When the helium in the core is exhausted, the core will contract further, becoming a carbon/oxygen white dwarf, while the remainder of our star gets blown back into interstellar space in a spectacular planetary nebula. For practically every star born with 40% to 800% of our Sun’s mass, the same fate awaits them all.

The white dwarf that we’re left with is always much less massive than the star it originated from, and never more massive than about 1.4 solar masses. Above this mass limit — known as the Chandrasekhar mass — a spontaneous thermonuclear reaction will occur: a type Ia supernova, destroying the white dwarf entirely. Driven by a series of curious observations, a team of scientists just discovered the most massive white dwarf ever robustly measured: between 1.327 and 1.365 solar masses, and it’s only 2,140 kilometers in radius, or barely larger than the Moon. It’s a fascinating find, but what it teaches us is truly phenomenal.

While we might look at our Solar System and our Sun as a “typical” example of what’s out there, it’s important to recognize that we’re only a sample size of 1, and that nature comes in all sorts of varieties. 95% of the stars in our galaxy are less massive than our Sun, but that remaining 5% means that approximately 20 billion stars in the Milky Way are more massive than we are. Additionally, about half of all the stars we know of are part of a system with two or more stars in them; singlet systems like our own are extremely common, but binaries, trinaries, and other multi-star configurations are quite common as well.

The reason this matters is that many binary systems are born with stars of similar masses, and hence they have similar fates. If one star in a binary system becomes a white dwarf, the other one likely won’t be far behind. The brightest star in our night sky, Sirius, has a white dwarf and a star more massive than the Sun orbiting one another; come back in about a billion years, and you’re almost certain to find two white dwarfs orbiting one another instead.

But that’s the beginning of the story, not the end. Just as binary black holes and neutron stars are known to inspiral and merge, so, too, will white dwarfs in binary systems. When they do, if their combined mass exceeds the Chandrasekhar limit, you’ll get a stellar cataclysm: a type Ia supernova, which can briefly shine as bright as some ~10 billion Suns.

But if their combined mass remains below that critical threshold instead — and keep in mind that some white dwarfs can be incredibly low in mass, with the lowest-mass one coming in at just ~17% the mass of the Sun — they’ll simply lead to the formation of another white dwarf. This new white dwarf should have some particular properties that set it apart from white dwarfs that form from single stars, so even if we only find a white dwarf post-merger, we should still be able to identify its origin. In particular, we expect:

  • a rapid rotation, from the conservation of angular momentum of inspiraling and merging stellar remnants,
  • a high mass, since two typical white dwarfs (of 1 solar mass or less) will combine to either lead to a supernova or a white dwarf of mass potentially comparable to the Chandrasekhar limit,
  • and a strong magnetic field at its surface, just like any rapidly rotating star or stellar remnant is anticipated to have.

All of that, however, is purely theoretical. Theoretical studies can be incredibly useful, particularly when those theories are informed by robust observations that paint a consistent picture. But it’s when we find new objects that push the limits of what’s possible that the biggest scientific advances — the ones that take us beyond what’s already been established — can often occur. Astronomically, one of the newest frontiers occurs in what we call time-domain astronomy: signals from the Universe that vary, in some fashion, on very short timescales.

One of the best tools we have to study these short-time changes is known as ZTF: the Zwicky Transient Facility. By monitoring a portion of the sky with excellent precision over a period of time, you can become sensitive to small, periodic changes in an object’s brightness. (This is something you automatically lose if you take a time-average of your data, and one of the greatest science losses that mega-constellations of satellites threaten to inflict on the field of astronomy.)

When looking at the ZTF data, astronomer Kevin Barnes noticed something unusual. One object in the sky — a faint, relatively nearby point of light — appeared to fainten and brighten periodically by about ~3% every 7 minutes: an incredibly short timescale for such a large variation. Even though ZTF scans the sky on much longer timescales, about every 48 hours, Barnes was able to pull this rapid, short-period signal out of the cumulative data.

Whenever you see something that’s unlike the other things you’ve seen before, even if you’re only first seeing it because of a technological advance, your instinct ought to be to try and understand precisely what’s happening. The way we do that, astronomically, is to attempt to determine as many properties of this object as possible, and the way we achieve that is by taking as many information-rich, complementary observations as possible.

The first hint of this object’s nature came by adding in the data from the ESA’s Gaia satellite. From its perch up above Earth’s atmosphere, Gaia can accurately measure the properties of stars, including their position and brightness, over long periods of time, like months and years. As the stars move through the galaxy and the Earth orbits the Sun, this enables us to infer the three-dimensional positions and proper motions of hundreds of millions, and perhaps even billions, of stars within our own galaxy.

When we traced this light source back to its identification in the Gaia data, we found that it was only ~130 light-years (about 40 parsecs) away. From its brightness, color, and distance, we can infer that it must be a white dwarf. And with such a large, periodic variation on merely ~7 minute timescales, that tells us something else: this white dwarf must be rotating incredibly quickly.

White dwarfs, you see, are typically about the size of rocky planets, even though their masses are comparable to that of a star. If you imagined, for example, cranking up the mass of the Earth until it was about 300,000 times as dense and massive as it is today, raised its temperature to somewhere around 10,000 K, but maintained its current size, you’d have something like a white dwarf. Only, for this particular white dwarf, it rotates a full 360° about its axis not in 24 hours, but every 7 minutes: 200 times as fast as the Earth. If you were to measure the speed of this white dwarf at its equator, you’d find it’s traveling at about 95 kilometers-per-second, or 340,000 kilometers-per-hour.

Why is a white dwarf so dense, and why does it spin so fast?

One reason is that you have so much mass together in one place, but no nuclear fusion to produce radiation. Without that extreme power output to “push back” against the force of gravity, the matter inside has no other option but to contract until something can counteract the pull of gravity. The only candidate left is the integrity of matter itself, and quantum rules like the Pauli Exclusion Principle, which prevent two identical subatomic (fermionic) particles from occupying the same quantum state. That’s where the Chandrasekhar mass limit comes from; go above a certain threshold, and even this quantum rule won’t be sufficient to stop you from collapsing. Once your total mass rises above that critical value, you’ll either trigger a set of runaway fusion reactions, or — if you’re already something like a neutron star — you’ll collapse completely: into a black hole.

One of the interesting things that happen to white dwarfs as they gain mass and approach this limit is that their physical size actually shrinks the more and more matter you add. The space between individual particles decreases, due to the gravitational force, by a greater amount than the cumulative addition of extra particles adds to the overall volume. As a result, the more massive your white dwarf gets — the closer in mass it gets to the Chandrasekhar limit — the smaller and smaller it gets. A white dwarf that’s less than half as massive as the Sun might be up to twice as big as the Earth, but white dwarfs that approach this mass limit can be smaller than even Mars.

When you see a heavy white dwarf, one close to this mass limit, there are a couple of ways it could have formed. You could either make one from a massive star that was just slightly below the mass limit needed for a supernova, or you could make it from the merger of two smaller, lower mass white dwarfs whose combined mass still didn’t quite reach that limit. Spins this fast — completing a full rotation in ~7 minutes — aren’t expected to arise from isolated, singlet stars that evolve into white dwarfs. It should have come from a merger, as its rotation period is comparable to that of the fastest-spinning white dwarf: 5 minutes, 17 seconds.

But, if it did arise that way, there’s another clue that we should be able to go out and look for: it should also have a strong magnetic field. Neither ZTF nor Gaia could provide that information, but follow up observations with other sophisticated instruments could.

That was where Ilaria Caiazzo, Caltech astronomer and lead author of this new study, came in. She spearheaded a slew of follow-up observations, including:

  • using the Keck I Telescope to perform spectroscopy on this object, breaking its light up into various individual wavelengths,
  • using the Swift observatory to obtain ultraviolet photometric data,
  • and using the Pan-STARRS survey data to obtain optical photometric data.

Combined with the ZTF (short-period brightening/faintening) and Gaia (parallax) data, the scientific team working on this project was able to extract an enormous amount of information about this object. What the observations indicated was that this white dwarf does possess a strong magnetic field: 800,000,000 Gauss (about one billion times stronger than Earth’s magnetic field), with variations of around ~25% over the surface of the white dwarf. The temperature of the white dwarf is very hot: 46,000 K, making it one of the hottest white dwarfs on record (possibly also indicating its youth), and also extremely small, with a radius of just 2,140 km.

This makes it the smallest white dwarf known, beating the prior record holders which came in around ~2,500 km. If we were to compare this white dwarf to objects in our Solar System, it would be smaller than even Mercury, and in between the sizes of Jupiter’s moons Callisto and Io: the 3rd and 4th largest moons in the Solar System. (Earth’s moon is 5th, if you’re curious.)

This new white dwarf — officially known as ZTFJ1901+1458 — has the smallest radius, the heaviest mass, and one of the shortest periods ever measured for this class of objects. Its large magnetic field points to an origin based in the merger of prior white dwarfs.

That does not, however, mean that white dwarfs like this are rare. Nor does it mean that white dwarfs don’t get heavier than this; estimates of the Chandrasekhar mass vary slightly based on rotation and composition: between 1.38 and 1.45 solar masses.

This white dwarf, whose mass is estimated to be between 1.327 and 1.365 solar masses, is certainly on the high end of the spectrum, but there ought to be white dwarfs that are really pushing this limit. In fact, one of them — a white dwarf orbiting a red giant in the T Coronae Borealis system — could very well be our galaxy’s next supernova. The white dwarf there is estimated to have a higher mass: 1.37 solar masses, but its uncertainties are also greater, as we cannot presently obtain a good radius measurement for it.

In fact, if ZTFJ1901+1458 were just two or three times farther away, we would not be able to make these precise measurements with our current set of observatories. For white dwarfs, it sets remarkable new records for size, mass, and magnetic field strength, but we also need to remind ourselves that we’re probing less than 0.001% of the white dwarfs in our galaxy at present.

In the future, however, the next generation of observatories, including the Vera Rubin Observatory, will be able to make these types of measurements over volumes more than a hundred times greater than our current set of observatories can probe. Moreover, new and upgraded neutrino observatories might even be able to start measuring the neutrinos produced by the electron capture process acting on various elements supposedly within the white dwarf. The presence or absence of elements like neon, sodium, or magnesium could all affect not only the neutrino spectrum produced, but the fate, evolution, and possibly even the death of these massive white dwarfs.

This is the smallest white dwarf ever found, and in theory they may be able to actually get as small as Earth’s moon, which has a radius that’s only about 20% smaller than this new record-holder of a white dwarf. Because of its fast rotation, its high temperature, and its strong magnetic field, it’s very likely that this white dwarf formed from the merger of two progenitor white dwarfs, and that the object we’re seeing now is no more than ~100 million years old: a blip in the lifetime of the Universe.

This discovery not only helps us understand the ultimate fate and the cosmic extremes of the remnants of all Sun-like stars, but showcases the power of time-domain astronomy. If we can monitor objects sufficiently well to detect small changes on very short timescales, we’ll have the potential to uncover phenomena that we’d never see any other way. But if we modify the night sky too severely to make that task physically impossible — as our growing mega-constellations are currently in the process of doing — this information will likely remain elusive for years, decades, or even generations to come.

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



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 –



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



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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