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James Webb Space Telescope: Sun shield is fully deployed – BBC News

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NASA

The new James Webb telescope has passed a major milestone in its quest to image the first stars to shine in the cosmos.

Controllers on Tuesday completed the deployment of the space observatory’s giant kite-shaped sun shield.

Only with this tennis court-sized barrier will Webb have the sensitivity to detect the signals coming from the most distant objects in the Universe.

Commissioning work will now concentrate on unpacking the telescope’s mirrors, the largest of which is 6.5m wide.

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The deployment of the five-membrane sun shield is a triumph for the engineering teams at the US space agency (Nasa) and the American aerospace manufacturer Northrop Grumman.

There were many who doubted the wisdom of a design that included so many motors, gears, pulleys and cables.

But years of testing on full-scale and sub-scale models paid dividends as controllers first separated the shield’s different layers and then tensioned them.

The fifth and final membrane – which like the other four had the thickness of a human hair – was locked into place at 16:58 GMT.

“Unfolding Webb’s sun shield in space is an incredible milestone, crucial to the success of the mission,” said Greg Robinson, Webb’s program director at Nasa Headquarters.

“Thousands of parts had to work with precision for this marvel of engineering to fully unfurl. The team has accomplished an audacious feat with the complexity of this deployment – one of the boldest undertakings yet for Webb.”

It’s worth noting that all the previous testing was done on Earth, under gravity conditions. This was the first time the shield had been unfurled in the unique “Zero-G” environment of space. “The first time, and we nailed it,” enthused Alphonso Stewart, Nasa’s Webb deployment systems lead.

“There was a lot of joy, a lot of relief,” added Hillary Stock, the sunshield deployments lead at Northrop.

Telescope comparisons

James Webb was launched on 25 December on an Ariane rocket from French Guiana.

The telescope is regarded as the successor to the Hubble space observatory which is now 31 years old and nearing the end of its operational life.

Webb will do similar science to Hubble but with the next-generation technologies that allow it to see deeper into the cosmos and, therefore, further back in time.

The expectation is that it will even catch the light from the pioneer stars that were first to ignite shortly after the Big Bang more than 13.5 billion years ago.

Critical to the whole endeavour, however, will be Webb’s sensitivity in the infrared. The light coming to the telescope from its targets at the edge of the observable Universe will arrive in this longer wavelength domain. And that means Webb must be cooled to fantastically cold temperatures or its own infrared glow will swamp the signals it’s trying to detect.

Hence the shield. The shade it casts will lower the environment around Webb’s mirrors and instruments to below minus 230C.

Secondary mirror

NASA

The controllers, who are based at the Space Telescope Science Institute (STScI) in Baltimore, Maryland, now have Webb’s golden mirrors in their sights.

Like the sun shield, the telescope’s two principal reflectors had to be folded to fit inside the nosecone of the Ariane.

Wednesday should see the 74cm-wide secondary mirror extended on 8m-long booms in front of the primary mirror.

The main mirror has “wings” that were tucked back for launch but which must now be rotated through 90 degrees to make a full, 6.5m-wide surface. Assuming things continue to run like clockwork, this should happen at the end of the week.

Webb is currently moving out to a position 1.5 million km from Earth on the planet’s “midnight” side. It’s from this location that it will study the Universe.

James Webb is a joint venture between the American, European and Canadian space agencies.

Deployment

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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.


Explore further

North Pole solar eclipse excited auroras on the other side of the world


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