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James Webb Space Telescope unfurls massive sunshield in major deployment milestone – Space.com

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One of the James Webb Space Telescope’s most nail-biting deployment steps is safely in the books.

The $10 billion observatory unfurled its huge sunshield on Friday (Dec. 31), carefully unfolding the five-layer structure by sequentially deploying two booms.

“Shine bright like a diamond. With the successful deployment of our right sunshield mid-boom, or ‘arm,’ Webb’s sunshield has now taken on its diamond shape in space,” mission team members said via Webb’s Twitter account Friday night.

Live updates: NASA’s James Webb Space Telescope mission
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The sunshield is one of the most crucial and complicated features of Webb, which launched on Dec. 25 to seek out faint heat signals from the early universe. Detecting such signals requires that Webb keep its instruments and optics extremely cold, and the sunshield will help it do just that by reflecting and radiating away solar energy.

The shiny silver shield measures 69.5 feet long by 46.5 feet wide (21.2 by 14.2 meters) when fully deployed — far too large to fit inside the protective payload fairing of any currently operational rocket. So it was designed to launch in a highly compact configuration and then unfold once Webb got to space.

That deployment is an elaborate, multistep process with many different potential failure points that could sink the entire mission.

“Webb’s sunshield assembly includes 140 release mechanisms, approximately 70 hinge assemblies, eight deployment motors, bearings, springs, gears, about 400 pulleys and 90 cables totaling 1,312 feet [400 m],” Webb spacecraft systems engineer Krystal Puga, who works at Northrop Grumman, the prime contractor for the mission, said in a video about Webb’s deployments that NASA posted in October.

Sunshield deployment began on Tuesday (Dec. 28) when Webb lowered the two pallets that hold the five-layer structure. Additional steps followed over the next few days. On Thursday (Dec. 30), for example, the observatory released the cover that had protected the sunshield during its time on Earth and launch to space.

That cover complicated Friday’s activities a bit: The Webb team delayed boom deployment by a few hours to make sure that the cover had fully rolled up as planned, and as needed.

“Switches that should have indicated that the cover rolled up did not trigger when they were supposed to,” Patrick Lynch, deputy chief of the communications office at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, wrote in a blog post Friday

“However, secondary and tertiary sources offered confirmation that it had,” Lynch added. “Temperature data seemed to show that the sunshield cover unrolled to block sunlight from a sensor, and gyroscope sensors indicated motion consistent with the sunshield cover release devices being activated.”

Webb team members initiated deployment of the port (lefthand) mid-boom at 1:30 p.m. EST (1830 GMT) on Friday, Lynch wrote, and the activity wrapped up at 4:49 p.m. EST (2149 GMT). Extension of the starboard mid-boom began at 6:31 p.m. EST (2331 GMT) and was done by around 10:13 p.m. EST (0313 GMT on Jan. 1), Lynch wrote in another blog post.

Related: Why the James Webb Space Telescope’s sunshield deployment takes so long

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Unfurling the sunshield is a huge milestone, so Webb team members are likely breathing big sighs of relief after Friday’s success. But the sunshield work isn’t done yet; its five thin Kapton layers must still be brought up to the proper tension, which the mission team aims to do over the weekend.

After that’s done, the focus will shift to deploying Webb’s secondary mirror and its 21.3-foot-wide (6.5 m) primary mirror. Those tasks are expected to be complete by Jan. 7 at the earliest, but deployment timelines are flexible, so don’t be shocked (or concerned) if that target isn’t met.

Locking the mirrors into their proper place will bring Webb’s complex main deployment phase to an end. The next major milestone to follow will be an engine burn, scheduled for 29 days after launch, that will insert Webb into orbit around its final destination: the Sun-Earth Lagrange Point 2 (L2), a gravitationally stable spot 930,000 miles (1.5 million kilometers) from our planet.

Webb team members will still have a lot of work to do after the observatory arrives at L2. They’ll have to precisely align the 18 segments of Webb’s primary mirror so the pieces work together as a single light-collecting surface, for example, and check out and calibrate the telescope’s four scientific instruments. 

Regular science operations are expected to start six months after launch, in the summer of 2022. For at least five years after that, Webb will study some of the universe’s first stars and galaxies, hunt for intriguing compounds in the atmospheres of nearby exoplanets and make a variety of other potentially transformative cosmic observations.

Mike Wall is the author of “Out There” (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook

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Here’s why whales don’t drown when they gulp down food underwater — ScienceDaily – newsconcerns

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Ever wondered whether whales can burp, and why they don’t drown when they gulp down gallons of water and krill? New UBC research may just hold the answer.

Researchers found that lunge-feeding whales have an ‘oral plug’, a fleshy bulb in their mouths that moves backwards to seal off the upper airways during feeding, while their larynx closes to block the lower airways.

This plug prevents water from entering their lungs when they feed, according to a paper published today in Current Biology. “It’s kind of like when a human’s uvula moves backwards to block our nasal passages, and our windpipe closes up while swallowing food,” says lead author Dr. Kelsey Gil, a postdoctoral researcher in the department of zoology.

Lunge-feeding whales eat by, you guessed it, lunging at their prey, accelerating at high speed and opening their mouths to engulf water and krill. Sometimes this amount can be larger than their own bodies, says Dr. Gil, an impressive feat given this group includes the humpback and the blue whale, the largest animal on Earth. Water is then drained via their baleen, leaving the tiny, tasty krill behind to be swallowed.

The researchers investigated fin whales specifically, a type of lunge-feeding whale and found the ‘oral plug’ needed to move in order to allow food to pass to the esophagus. The only way it could was towards the back of the head, and up, blocking off the nasal passages when the whale swallows. Simultaneously, cartilage closes at the entrance to the larynx, and the laryngeal sac moves upwards to block off the lower airways, says Dr. Gil. “We haven’t seen this protective mechanism in any other animals, or in the literature. A lot of our knowledge about whales and dolphins comes from toothed whales, which have completely separated respiratory tracts, so similar assumptions have been made about lunge-feeding whales.”

It turns out humans have a similar system to swallow food without getting anything in their lungs: we have the epiglottis and soft palate, a ‘lid’ of cartilage and a flap of muscle in our throat and mouth, respectively. Humans could probably eat underwater as well, says Dr. Gil, but it would be rather like swimming at high speed towards a hamburger and opening your mouth wide as you approached — difficult not to flood your lungs.

The whales’ oral plug and closing larynx is central to how lunge-feeding evolved, a key component in the enormous size of these creatures, the researchers say. “Bulk filter-feeding on krill swarms is highly efficient and the only way to provide the massive amount of energy needed to support such large body size. This would not be possible without the special anatomical features we have described,” says senior author Dr. Robert Shadwick, a professor in the UBC department of zoology.

Investigating whale anatomy often involves trying to dissect whales that have died from stranding which comes with such challenges as trying to complete work before the tide rises. However, for this research, Dr. Gil and her colleagues dissected whales in Iceland in 2018, recovering tissue that wasn’t being used for food from a commercial whaling station. Working with whales in real-time would be wonderful, she says, but might require some advancements in technology. “It would be interesting to throw a tiny camera down a whale’s mouth while it was feeding to see what’s happening, but we’d need to make sure it was safe to eat and biodegradable.”

The team will continue to explore the mechanisms related to the pharynx, and of the small esophagus that is responsible for rapidly transporting hundreds of kilograms of krill to the stomach in less than a minute. With the many human impacts that disrupt food chains, and knowing how whales feed and how much they eat, it’s good to know as much as possible about these animals in order to protect them and their eco systems, says Dr. Gil.

And there’s plenty more to find out, including whether whales cough, hiccup, and yes, burp. “Humpback whales blow bubbles out of their mouth, but we aren’t exactly sure where the air is from — it might make more sense, and be safer, for whales to burp out of their blowholes.”

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The drifting giant A68 iceberg released billions of tons of fresh water in South Georgia ecosystem – MercoPress

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Saturday, January 22nd 2022 – 10:56 UTC

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Satellite images shows A68a heading towards the sub-Antarctic island of South Georgia. Credit: MODIS from NASA Worldview Snapshots

Scientists monitoring the giant A68a iceberg from space reveal that a huge amount of freshwater was released as it melted around the sub-Antarctic island of South Georgia. An estimated 152 billion tons of freshwater – equivalent to 20 x Loch Ness or 61 million Olympic sized swimming pools, entered the seas around the sub-Antarctic island of South Georgia when A68a melted over three months in 2020/2021, according to a new study published this month by the British Antarctic Survey.

In July 2017, A68a calved off the Larsen-C Ice Shelf on the Antarctic Peninsula and began its epic three-and-a-half year, 4.000 km journey across the Southern Ocean. At 5719 square kilometers – about a quarter the size of Wales – it was the biggest iceberg on Earth when it formed and the sixth largest on record. Around Christmas 2020, the berg received widespread attention as it drifted worryingly close to South Georgia, raising concerns it could harm the island’s fragile ecosystem.

A team from Center for Polar Observation and Modeling and BAS used satellite measurements to chart the iceberg’s area and thickness change throughout its life cycle. The authors show that the iceberg had melted enough as it drifted to avoid damaging the sea floor around South Georgia by running aground. However, a side effect of the melting was the release of a colossal 152 billion tons of fresh water in close proximity to the island – a disturbance that could have a profound impact on the island’s marine habitat.

For the first two years of its life, A68a stayed close to Antarctica in the cold waters of the Weddell Sea and experienced little in the way of melting. However, once it began its northwards journey across the Drake Passage it traveled through increasingly warm waters and began to melt. Altogether, the iceberg thinned by 67 meters from its initial 235 m thickness, with the rate of melting rising sharply as the berg drifted around South Georgia.

Laura Gerrish, GIS and mapping specialist at BAS and co-author of the study said, “A68 was an absolutely fascinating iceberg to track all the way from its creation to its end. Frequent measurements allowed us to follow every move and break-up of the berg as it moved slowly northwards through an area called ‘iceberg alley’, a route in the ocean which icebergs often follow, and into the Scotia Sea where it then gained speed and approached the island of South Georgia very closely.”

If an iceberg’s keel is too deep it can become grounded on the sea floor. This can be disruptive in several different ways; the scour marks can destroy fauna, and the berg itself can block ocean currents and predator foraging routes. All of these potential outcomes were feared when A68a approached South Georgia. However, this new study reveals that it collided only briefly with the sea floor and broke apart shortly afterwards, making it less of a risk in terms of blockage. By the time it reached the shallow waters around South Georgia, the iceberg’s keel had reduced to 141 meters below the ocean surface, shallow enough to avoid the seabed which is around 150 meters deep.

Nevertheless, the ecosystem and wildlife around South Georgia will certainly have felt the impact of the colossal iceberg’s visit. When icebergs detach from ice shelves, they drift with the ocean currents and wind while releasing cold fresh melt-water and nutrients as they melt. This process influences the local ocean circulation and fosters biological production around the iceberg. At its peak, the iceberg was melting at a rate of 7 meters per month, and in total it released a staggering 152 billion tons of fresh water and nutrients.

“This is a huge amount of melt water, and the next thing we want to learn is whether it had a positive or negative impact on the ecosystem around South Georgia. Because A68a took a common route across the Drake Passage, we hope to learn more about icebergs taking a similar trajectory, and how they influence the polar oceans,” said Anne Braakmann-Folgmann, a researcher at CPOM and PhD candidate at the University of Leeds’ School of Earth and Environment, and lead author of the study.

The journey of A68a has been charted using observations from five different satellites. The iceberg’s area change was recorded using a combination of Sentinel-1, Sentinel-3, and MODIS imagery. Meanwhile, the iceberg’s thickness change was measured using CryoSat-2 and ICESat-2 altimetry. By combining these measurements, the iceberg’s area, thickness, and volume change were determined.

Tommaso Parrinello, CryoSat Mission Manager at the European Space Agency pointed out that “Our ability to study every move of the iceberg in such detail is thanks to advances in satellite techniques and the use of a variety of measurements. Imaging satellites record the location and shape of the iceberg and data from altimetry missions add a third dimension as they measure the height of surfaces underneath the satellites and can therefore observe how an iceberg melts.”

“Observing the Disintegration of the A68A Iceberg from Space” is published in the journal Remote Sensing of Environment at https://doi.org/10.1016/j.rse.2021.112855.

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Are the northern lights caused by 'particles from the Sun'? Not exactly – Phys.org

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Credit: PhotoVisions/Shutterstock

What a spectacle a big aurora is, its shimmering curtains and colorful rays of light illuminating a dark sky. Many people refer to aurora as the northern lights (the aurora borealis), but there are southern lights too (the aurora australis). Either way, if you’re lucky enough to catch a glimpse of this phenomenon, it’s something you won’t soon forget.

The is often explained simply as “particles from the Sun” hitting our atmosphere. But that’s not technically accurate except in a few limited cases. So what does happen to create this natural marvel?

We see the aurora when energetic charged particles—electrons and sometimes ions—collide with atoms in the upper atmosphere. While the aurora often follows explosive events on the Sun, it’s not quite true to say these energetic particles that cause the aurora come from the Sun.

Earth’s magnetism, the force that directs the compass needle, dominates the motions of electrically charged particles in space around Earth. The magnetic field near the surface of Earth is normally steady, but its strength and direction fluctuate when there are displays of the aurora. These fluctuations are caused by what’s called a magnetic substorm—a rapid disturbance in the in near-Earth space.

To understand what happens to trigger a substorm, we first need to learn about . Plasma is a gas in which a significant number of the atoms have been broken into ions and electrons. The gas of the uppermost regions of Earth’s atmosphere is in the , as is the gas that makes up the Sun and other stars. A gas of plasma flows away continuously from the Sun: this is called the solar wind.

Plasma behaves differently from those gases we meet in everyday life. Wave a magnet around in your kitchen and nothing much happens. The air of the kitchen consists overwhelmingly of electrically neutral atoms, so it’s quite undisturbed by the moving magnet. In a plasma, however, with its electrically charged particles, things are different. So if your house was filled with plasma, waving a magnet around would make the air move.

When solar wind plasma arrives at the earth it interacts with the planet’s magnetic field (as illustrated below—the magnetic field is represented by the lines that look a bit like a spider). Most of the time, plasma travels easily along the lines of the magnetic field, but not across them. This means that solar wind arriving at Earth is diverted around the planet and kept away from the Earth’s atmosphere. In turn, the solar wind drags the field lines out into the elongated form seen on the night side, called the magnetotail.

Sometimes moving plasma brings magnetic fields from different regions together, causing a local breakdown in the pattern of magnetic field lines. This phenomenon, called magnetic reconnection, heralds a new magnetic configuration, and, importantly, unleashes a huge amount of energy.

These events happen fairly often in the Sun’s outer atmosphere, causing an explosive energy release and pushing clouds of magnetized gas, called coronal mass ejections, away from the Sun (as seen in the image above).

If a arrives at Earth it can in turn trigger reconnection in the magnetotail, releasing energy that drives electrical currents in near-Earth space: the substorm. Strong electric fields that develop in this process accelerate electrons to high energies. Some of these electrons may have come from the , allowed into near-Earth space by reconnection, but their acceleration in the substorm is essential to their role in the aurora.

These particles are then funneled by the magnetic towards the atmosphere high above the polar regions. There they collide with the oxygen and nitrogen atoms, exciting them to glow as the aurora.

Now you know exactly what causes the northern lights, how do you optimize your chances of seeing it? Seek out dark skies far from cities and towns. The further north you can go the better but you don’t need to be in the Arctic Circle. We see them from time to time in Scotland, and they’ve even been spotted in the north of England—although they’re still better seen at higher latitudes.

Websites such as AuroraWatch UK can tell you when it’s worth heading outside. And remember that while events on the Sun can give us a few days warning, these are indicative, not foolproof. Perhaps part of the magic lies in the fact that you need a little bit of luck to see the aurora in all its glory.


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Are the northern lights caused by ‘particles from the Sun’? Not exactly (2022, January 21)
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