Betelgeuse going Critical

Betelgeuse may explode any moment, between now and a 100 000 years from now. Which is almost the same as ‘now’ in astrophysical terms. Of course, in human lifespan terms, the chances of me witnessing this great event are slim. Nonetheless, Betelgeuse caused quite a fuss in 2019, when it suddenly dimmed so much that the difference was noticeable to the naked eye (see Fig. 1). Later, it began brightening again. One specific explanation of dust blocking off part of the star’s light in our direction has since manifested itself. Compared to our sun, Betelgeuse truly is a giant. It’s radius is somewhere between 600 to 880 times larger than the sun and if Betelgeuse were our host star in place of the sun, the orbit of Jupiter would still be below its surface. But, while outdoing our local star in almost every aspect, there is one way our sun comes out on top: age. Betelgeuse is merely 8 million years old and already considered a case for the stellar grim reaper. For comparison, the sun has existed for around 4 billion years and is thought to be at roughly the half point of its life. The size of Betelgeuse causes the fuel necessary for the nuclear fusion inside it to be used up quicker and forebodes a violent end, when its massive gravitational forces win the struggle against the radiation energy and come crashing down. This violent death of massive stars such as Betelgeuse is called a supernova. 

Early Warning

The authors of today’s paper have taken a look at the long term development of Betelgeuse, from the beginning of modern observations of the star in the 1980s.

Early warnings for an impending change within a dynamical system (stars are no unvarying objects, they are subjected to constant changes and motion within them) can be noted when observing the long term light curve of an object preceding an event, in this case, the dimming episode.

Previous works have pointed out that if dust were responsible, there should have been an excess of infrared light observed close to the dimming as well as a reduction in polarized light due to it passing the dust. Both conditions could not be met according to detailed measurements and analysis.

Any dynamical system can exist in several possible states. These states evolve in a specific pattern and exist for a particular parameter combination. Certain transitions between states- called critical transitions-involve major changes to the dynamical behaviour of the system. They may be caused by only small changes to the parameters of the system.

The authors argue that the dimming event could have occurred due to a critical transition in the pulsation dynamics of Betelgeuse. This means that the nature of the system dynamics underwent a drastic change.

Winds of Change

Other works have shown that several quantities of a time series (such as the light curve) increase leading up to a critical transition of the system. Three of these quantities explored in this work are the autocorrelation, the variance and the so-called detrended fluctuation analysis (DFA). If the change in Betelgeuse’s brightness was indeed due to a critical transition in pulsation dynamics, then that should be imprinted on these quantifiers.

Autocorrelation is, simply speaking, the similarity of a signal observed at different times as a function of the time lag between them. This allows for the detection of repeating patterns, such as periodic signals which would otherwise be buried by noise. 

The variance measures the scatter of the data points around their mean value.
The DFA initially turns the data into a cumulative (so each measurement added on top of the previous) amplitude time series. The root mean square of the deviation is the fluctuation of the linear trend and is expected to rise as a power-law with respect to time. The exponent of this is called the Hurst exponent .

Examining these three quantifiers has also been applied in fields outside astronomy, such as ecology, engineering and psychiatry. The authors of today’s paper thus come from a diverse set of fields, including medicine, complex systems, physics and astrophysics, to optimally apply expertise.

Since there is a large number of gaps within the data between 1980 and 1990, the trends for the autocorrelation, variance, and ⍺ are analyzed for the data from 1990 onwards. The resulting plots are shown in Fig. 2.

Fig. 2: Autocorrelation Function, variance and Hurst exponent of Betelgeuse’s light curve over time. Indicated in gray are measurements before 1990, in green after 1990.
(Fig. 1 in the author’s paper)

For all three quantifiers, the values increase over time before the dimming event begins. This implies that a dynamical transition within Betelgeuse led to the decreasing subsequently increasing brightness in 2019/2020.

Other works point out another possible dimming event in the mid to late 1980s, which might explain the change of the general trend of the quantifiers at that point.
Further analysis based on the number of repeating states of the system, how deterministic the dynamics appear to be and the extent of laminar (i.e. non-turbulent) phases has been conducted by the authors. These measures show again a gradual increase leading up to the dimming phase.

A new Era for Betelgeuse

The authors conclude that the signature of the impending change in the dynamic system of Betelgeuse had been observable a long time preceding the event.

While there is evidence against a dust cloud being responsible for the dimming of Betelgeuse, it has also been shown before that the effective temperature of the star was not decreased significantly during the event, which most likely eliminates convection driven dimming, i.e. a temporary cooler period of the surface.

The authors stress that the final remaining option is a change in the pulsation dynamics of Betelgeuse, causing the 2019-2020 change in brightness.
It is still not proven decisively what caused the dimming, but the authors mention that such a critical transition would imply lasting changes for the system, detectable in the future. Thus, continuous observation of Betelgeuse could give us important new information and help to solve this puzzle.

Betelgeuse is the 10th brightest star in our night sky, so easy to spot. I would suggest, keep an eye on it. Just in case.

Astronomers have discovered a super-Jupiter orbiting its young star on a surprisingly wide orbit. How did it get there?

Scientists have just obtained images of giant planet around a young star about 360 light-years away in the southern constellation Musca, the Fly. The planet is a gas giant, not an unusual find in itself. However, it’s located about 110 times farther from its star than Earth is from the Sun, and astronomers are puzzled how such a large planet could have formed so far from its star. Their findings will appear in Astronomy & Astrophysics (preprint available here). The planet, YSES 2b, was found as part of the Young Suns Exoplanet Survey (YSES), which began monitoring 70 stars resembling the infant Sun in 2017. The survey uses the Very Large Telescope of the European Southern Observatory in Chile, making use of SPHERE instrument to block light from stars so that surrounding planets can be seen directly. Because this is a young system, just 14 million years old, the planet itself is still glowing with infrared radiation as it cools and shrinks. The researchers found that the planet has a mass of about six Jupiters. Normally, planets of comparable mass form closer to their star via core accretion. During this process, dust particles from the protoplanetary disk stick to each other to form small rocky cores, which then gather large gaseous envelopes around themselves. Most astronomers think the solar system’s planets formed in this way, though there are still some open questions about the details.

But due to its distance, YSES 2b can’t have formed this way. Grains in the disk tend to flow inward, so they would not last long enough on the disk’s outskirts for the gradual process of core accretion to take place. “At distances this far away from the star, core accretion could not produce a planetary core that is massive enough to accrete a gaseous atmosphere,” says lead researcher Alexander Bohn (Leiden University, The Netherlands).

Alternatively, YSES 2b might have formed by gravitational instability. According to this scenario, denser regions of the star’s disk suddenly collapse in on themselves to form the core of a planet. The problem with this model, says Bohn, is that computer simulations show that gravitational instability would create much more massive objects: brown dwarfs with the mass of at least 13 Jupiters.

But Ken Rice (University of Edinburgh, UK), who was not involved in the study, disagrees. “It is true that we might expect planets that form via gravitational instability often to grow to become brown dwarfs,” he says. “But computer simulations actually show that they probably start as less massive objects (maybe a few Jupiter masses) and so it certainly seems possible for gravitational instability to form something with a mass of around 6 Jupiter masses.”

Bohn’s group, however, thinks that a third scenario might be at play. It’s possible, he says, that that YSES 2b was formed through core accretion closer to its star — but the gravitational pull of another planet then pulled it to a farther-out orbit. To confirm this process, the scientists would have to discover another planet. They hope further observations will give them that opportunity.

Astronomers Detect a New Super-Earth Orbiting a Red Dwarf Star

In recent years there has been an exhaustive study of red dwarf stars to find exoplanets in orbit around them. These stars have effective surface temperatures between 2400 and 3700 K (over 2000 degrees cooler than the Sun), and masses between 0.08 and 0.45 solar masses. In this context, a team of researchers led by Borja Toledo Padrón, a Severo Ochoa-La Caixa doctoral student at the Instituto de Astrofísica de Canarias (IAC), specializing in the search for planets around this type of stars, has discovered a super-Earth orbiting the star GJ 740, a red dwarf star situated some 36 light years from the Earth. The planet orbits its star with a period of 2.4 days and its mass is around 3 times the mass of the Earth. Because the star is so close to the Sun, and the planet so close to the star, this new super-Earth could be the object of future researches with very large diameter telescopes towards the end of this decade. The results of the study were recently published in the journal Astronomy & Astrophysics. “This is the planet with the second shortest orbital period around this type of star. The mass and the period suggest a rocky planet, with a radius of around 1.4 Earth radii, which could be confirmed in future observations with the TESS satellite,” explains Borja Toledo Padrón, the first author of the article. The data also indicate the presence of a second planet with an orbital period of 9 years, and a mass comparable to that of Saturn (close to 100 Earth masses), although its radial velocity signal could be due to the magnetic cycle of the star (similar to that of the Sun), so that more data are needed to confirm that the signal is really due to a planet.

The Kepler mission, recognized at one of the most successful in detecting exoplanets using the transit method (which is the search for small variations in the brightness of a star caused by the transit between it and ourselves of planets orbiting around it), has discovered a total of 156 new planets around cool stars. From its data, it has been estimated that this type of star harbors an average of 2.5 planets with orbital periods of less than 200 days. “The search for new exoplanets around cool stars is driven by the smaller difference between the planet’s mass and the star’s mass compared with stars in warmer spectral classes (which facilitates the detection of the planets’ signals), as well as the large number of this type of star in our Galaxy,” comments Borja Toledo Padrón.

Cool stars are also an ideal target for the search for planets via the radial velocity method. This method is based on the detection of small variations in the velocity of a star due to the gravitational attraction of a planet in orbit around it, using spectroscopic observations. Since the discovery in 1998 of the first radial velocity signal of an exoplanet around a cool star, until now, a total of 116 exoplanets has been discovered around this class of stars using the radial velocity method. “The main difficulty of this method is related to the intense magnetic activity of this type of stars, which can produce spectroscopic signals very similar to those due to an exoplanet,” says Jonay I. González Hernández, an IAC researcher who is a co-author of this article.

Reference: “A super-Earth on a close-in orbit around the M1V star GJ 740: A HADES and CARMENES collaboration” by B. Toledo-Padrón, A. Suárez Mascareño, J. I. González Hernández, R. Rebolo,, M. Pinamonti, M. Perger, G. Scandariato, M. Damasso, A. Sozzetti, J. Maldonado, S. Desidera, I. Ribas, G. Micela, L. Affer, E. González-Alvarez, G. Leto, I. Pagano, R. Zanmar Sánchez, P. Giacobbe, E. Herrero, J. C. Morales, P. J. Amado, J. A. Caballero, A. Quirrenbach, A. Reiners and M. Zechmeister, 7 April 2021, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202040099

The study is part of the project HADES (HArps-n red Dwarf Exoplanet Survey), in which the IAC is collaborating with the Institut de Ciències de l’Espai (IEEC-CSIC) of Catalonia, and the Italian program GAPS (Global Architecture of Planetary Systems), whose objective is the detection and characterization of exoplanets round cool stars, in which are being used HARPS-N, on the Telescopio Nazionale Galileo (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma). This detection was possible due to a six year observing campaign with HARPS-N, complemented with measurements with the CARMENES spectrograph on the 3.5m telescope at the Calar Alto Observatory (Almería) and HARPS, on the 3.6m telescope at the La Silla Observatory (Chile), as well as photometric support from the ASAP and EXORAP surveys. Also participating in this work are IAC researchers Alejandro Suárez Mascareño, and Rafael Rebolo.

Nearest Exoplanet to Our Solar System: Jupiter-Mass Planet Orbiting Epsilon Eridani

This artist’s concept is of a Jupiter-mass planet orbiting the nearby star Epsilon Eridani. Located 10.5 light-years away, it was the closest known exoplanet to our solar system when it was discovered in 2007. The planet is in an elliptical orbit that carries it as close to the star as Earth is from the Sun, and as far from the star as Jupiter is from the Sun. Epsilon Eridani is a young star, only 800 million years old. It is still surrounded by a disk of dust that extends 20 billion miles from the star. The disk appears as a linear sheet of reflecting dust in this view because it is seen edge-on from the planet’s orbit, which is in the same plane as the dust disk. The planet’s rings and satellites are purely hypothetical in this view, but plausible. As a gas giant, the planet is uninhabitable for life as we know it. However, any moons might have conditions suitable for life. Astronomers determined the planet’s mass and orbital tilt in 2006 by using Hubble to measure the unseen planet’s gravitational pull on the star as it slowly moved across the sky. Evidence for the planet first appeared in 2000 when astronomers measured a telltale wobble in the star.

This is an artist’s concept of a Jupiter-mass planet orbiting the nearby star Epsilon Eridani. Credit: NASA, ESA, and G. Bacon (STScI)

NASA's Insight Mars Lander Is 'in Crisis', And Has Entered Emergency Hibernation

NASA's $800 million Mars lander is in an energy crisis. InSight, which landed in a Martian plain called Elysium Planitia in 2018, has detected more than 500 Mars quakes, felt more than 10,000 dust devils pass by, and started to measure the planet's core. But over the past few months, InSight has been fighting for its life as the red planet's unpredictable weather threatens to snuff out the robot. Unlike other sites where NASA has sent rovers and landers – including the landing spot of the new Perseverance rover and its Mars helicopter – powerful gusts of wind have not been sweeping Elysium Planitia. These winds, called "cleaning events," are needed to blow the red Martian dust off the solar panels of NASA's robots. Without their help, a thick layer of dust has accumulated on InSight, and it's struggling to absorb sunlight. InSight's solar panels were producing just 27 percent of their energy capacity in February, when winter was arriving in Elysium Planitia. So NASA decided to put the lander in "hibernation mode," switching off different instruments each day. Soon the robot will shut down all functions that aren't necessary for its survival. By pausing its scientific operations, the lander should be able to save enough power to keep its systems warm through the frigid Martian nights, when temperatures can drop to negative-130 degrees Fahrenheit.

"The amount of power available over the next few months will really be driven by the weather," Chuck Scott, InSight's project manager, said in a statement.

Now almost halfway through its expected hibernation period, InSight is still in good condition, but the risk of a potentially fatal power failure is ever-present. If the lander's batteries die, it might never recover.

"We would be hopeful that we'd be able to bring it back back to life, especially if it's not asleep or dead for a long period of time," Bruce Banerdt, InSight's principal investigator, told Insider. "But that would be a dicey situation."

The agency expects to restart InSight's full operations after Mars swings back toward the sun in July. If it can survive this Martian winter, the lander could keep listening for quakes and tracking weather into 2022.

InSight's power shortage contributed to NASA's decision to abandon the lander's "mole" in January. That burrowing probe was supposed to measure the temperature deep in the Martian crust – crucial data in the study of the planet's history and internal structure.

Now scientists are missing out on even more data as the lander shuts down its instruments. Its Mars weather measurements have become scarce, and in the next month or so, it will stop listening for quakes.

Banerdt said he fears the lander could miss some big quakes, but it's worth it to keep the robot alive. If InSight's batteries die, he added, "it's a good zombie spacecraft" – meaning it's programmed to recharge and start up again once the sun comes out.

"The problem with that scenario is that in the meantime, the spacecraft is very, very cold. And this is happening during the coldest part of the year for the spacecraft," Banerdt said. "A lot of the electronics is pretty delicate. And it's, unfortunately, pretty likely that something would be damaged by the cold."

Banerdt suspects that's what happened to the Spirit and Opportunity rovers. Both ran out of energy on the Martian surface and were unable to power up again. He's hopeful that InSight won't have to die, though.

"Right now, our predictions, our projections are that we should be able to make it through the lowest-power point and come out the other side," Banerdt said.

Still, an odd dust storm in the next four or five months could tip the scales by piling more dirt onto InSight's solar panels. That's what happened to Opportunity. But luckily, it's not dust-storm season.

"We think we're pretty well off, but Mars is unpredictable. We never know exactly what's going to happen," Banerdt said.

Astronomers inspect open cluster NGC 1348

By analyzing data from various astronomical surveys, astronomers have performed an exhaustive photometric and kinematical study of an open cluster known as NGC 1348. The new research, detailed in a paper published April 2 on arXiv dot org, provides important information regarding the parameters of this cluster. Open clusters (OCs), formed from the same giant molecular cloud, are groups of stars loosely gravitationally bound to each other. So far, more than 1,000 of them have been discovered in the Milky Way, and scientists are still looking for more, hoping to find a variety of these stellar groupings. Expanding the list of known galactic open clusters and studying them in detail could be crucial for improving our understanding of the formation and evolution of our galaxy. Located some 6,000 light years away from the Earth, NGC 1348 (also known as OCL 391) is a galactic OC estimated to be at least 50 million years old. Although NGC 1348 was discovered in 1790, it remains a poorly studied cluster, as to date, only several detailed observations of this object have been conducted. A team of astronomers led by Devendra Bisht of the University of Science and Technology of China (USTC) in Hefei, China, took a closer look at NGC 1348 in order to shed more light on its properties. For this purpose, they analyzed data from ESA's Gaia satellite, NASA's WISE spacecraft and the Pan-STARRS1 telescope. The study was complemented by datasets from the UKIRT InfraRed Deep Sky Surveys (UKIDSS) and the AAVSO Photometric All-Sky Survey (APASS).

"We extracted photometric data of the cluster within a 10 arcmin radius from the APASS, PanSTARRS1, UKIDSS and WISE along with astrometric data from GAIA EDR3. The main purpose is to take different photometric surveys' data to check the extinction law towards the open cluster NGC 1348 from the optical to the mid-infrared. After cross-matching all these catalogs, the fundamental parameters, mass function, galactic orbits and kinematics have been studied in the current paper," the researchers explained.

The team identified 438 member stars of NGC 1348 with membership probabilities higher than 50% and brighter than 20 mag. The selected sample of stars was used to derive the cluster's fundamental parameters.

The radius of NGC 1348 was calculated to be some 18.48 light years or 7.5 arcmins, while its tidal radius was estimated to be nearly 30 light years. The mean proper motions of the cluster were measured to be approximately 1.27 and −0.73 mas/year in the right ascension and declination directions, respectively.

The study found that NGC 1348 is located about 8,500 light years away, therefore farther than previously thought. The age of the cluster was estimated to be around 160 million years, what is based on comparing the color-magnitude diagram with theoretical isochrones.

Moreover, the research detected a mass segregation effect in NGC 1348 and found that the mass function slope is at a level of 1.3, in the mass range between 1.0 and 4.1 solar masses. According to the authors of the paper, the results suggest that NGC 1348 is a dynamically relaxed OC.

Hubble telescope finds rare double quasars in ancient galactic collisions

NASA's Hubble Space Telescope has captured not one but two pairs of distant quasars that existed some 10 billion years ago, a new study reports. According to the team leading the research, the discovery was like finding a needle in a haystack, as the chance of locating a double quasar compared to a single quasar is just one in 1,000. Imagery captured by the long-serving space telescope shows that the quasars within each pair are only about 10,000 light-years apart. For comparison, our sun is 26,000 light-years away from the supermassive black hole at the heart of the Milky Way. The researchers, led by Nadia Zakamska of Johns Hopkins University in Baltimore, Maryland, believe that the quasars are knitted so closely to each other because each pair lies at the center of two galaxies in the midst of a smashup. A quasar is an intense emission of light from the center of a galaxy that's fuelled by the gluttonous supermassive black hole at its core. "Quasars make a profound impact on galaxy formation in the universe," Zakamska said in a statement released on April 6. When two galaxies collide, their intense gravity causes the structures to become warped. More material is funneled into their respective black holes as a result, igniting their quasars. Over time, the intense radiation fuels galactic winds that strip away most of the gas from the merging galaxies.

This process results in the formation of an elliptical galaxy. A similar sequence is predicted to happen a few billion years from now when the Milky Way merges with its nearest galactic neighbor, the Andromeda galaxy.

More than 100 double quasars have been discovered in merging galaxies, though none are as old as the two pairs found in this study. The newly discovered quasars are from an era associated with an abundance of quasar formation, about 10 billion years ago. Astronomers had previously suggested there should be myriad dual quasars during that time, but none had been detected until now.

"This truly is the first sample of dual quasars at the peak epoch of galaxy formation with which we can use to probe ideas about how supermassive black holes come together to eventually form a binary," Zakamska said.

The discovery of these four quasars not only informs researchers on the merging of supermassive black holes in the early universe, but also highlights the benefits of employing a variety of techniques to detect and image elusive dual quasars, study team members said.

Although Hubble is the only telescope with a high enough resolution to distinguish these two close quasar pairs, its sharp eye wasn't quite good enough to locate them on its own. Astronomers needed to point Hubble in the right direction, and for that they enlisted the help of the European Space Agency's star-mapping Gaia satellite and the ground-based Sloan Digital Sky Survey to compile a list of possible candidates for Hubble to investigate.

When the researchers then observed the first four targets with Hubble, they found that two of the targets were actually two pairs of close quasars. The researchers said it was a "light bulb moment" that reaffirmed their plans to use Hubble, Sloan and Gaia to search for quasar duos.
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"The new technique can not only discover dual quasars much further away, but it is much more efficient than the methods we've used before," said Xin Liu of the University of Illinois at Urbana-Champaign, who was also part of the study.

The team's research appears in the April 1 online issue of the journal Nature Astronomy.

NASA’s Webb Telescope Packs Its Sunshield for a Million Mile Trip

Engineers working on NASA’s James Webb Space Telescope have successfully folded and packed its sunshield for its upcoming million-mile (roughly 1.5 million kilometer) journey, which begins later this year. The sunshield — a five-layer, diamond-shaped structure the size of a tennis court — was specially engineered to fold up around the two sides of the telescope and fit within the confines of its launch vehicle, the Ariane 5 rocket. Now that folding has been completed at Northrop Grumman in Redondo Beach, California, the sunshield will remain in this compact form through launch and the first few days the observatory will spend in space. Designed to protect the telescope’s optics from any heat sources that could interfere with its sight, the sunshield is one of Webb’s most critical and complex components. Because Webb is an infrared telescope, its mirrors and sensors need to be kept at extremely cold temperatures to detect faint heat signals from distant objects in the universe. In space, one side of the sunshield will always reflect light and background heat from the Sun, Earth and Moon. Thermal models show that the maximum temperature of the outermost layer is 383 Kelvin, or about 230 degrees Fahrenheit. Meanwhile, the other side of the sunshield will always face deep space, with the coldest layer having a modeled minimum temperature of 36 Kelvin, or about minus 394 degrees Fahrenheit. Fully deployed, the telescope’s sunshield measures almost 70 feet by 47 feet (21 meters by 14 meters). When stowed inside the rocket for launch, the folded sunshield will be packaged in a very confined area in between other structures of the observatory to accommodate the limited space inside the 18-foot (5.4-meter) diameter rocket fairing.

Both sides of the James Webb Space Telescope's sunshield were lifted vertically in preparation for the folding of the sunshield layers. Credits: NASA/Chris Gunn

“There is nothing really analogous to what we are trying to achieve with the folding up of a tennis court-sized sunshield, but it is similar to packing a parachute,” said Jeff Cheezum, a lead sunshield design engineer at Northrop Grumman. “Just like a skydiver needs their parachute packed correctly in order to open perfectly and to successfully get back to Earth, Webb needs its sunshield to be perfectly stowed to ensure that it also opens up perfectly and maintains its shape, in order to successfully keep the telescope at its required operating temperature.”

                                        

During the sunshield folding process for the James Webb Space Telescope, a team of technicians carefully fold each layer in a zigzag pattern to create accordion-like stacks of membranes on either side of the telescope.

Credits: NASA/Chris Gunn

The month-long process of folding the sunshield began with laying the five layers as flat as possible. In its deployed state, the sunshield resembles a multilayered silver ship, so its inherently curved surfaces added a degree of complexity to this step. Afterwards, the layers were lifted vertically and propped onto special support equipment so that they could be properly restrained for folding. A team of technicians then carefully folded each layer in a zigzag pattern to create accordion-like stacks of membranes on either side of the telescope.

The first layer of the sunshield is two-thousandths of an inch (0.005 centimeters) thick, while the other four layers are only one-thousandth of an inch thick. For the team, a built-in challenge was the delicacy of folding such thin layers. The folding process also had to account for components such as the sunshield’s 90 different tensioning cables, which must be stowed in a specific manner to ensure the sunshield deploys smoothly.

With the successful completion of sunshield folding, the engineering team has prepared the sunshield for its complex deployment in space. The sunshield will unfold at the end of the telescope’s first week in space after launch, stretching out to its full size and then separating and tensioning each of its five layers. Testing for this unfolding and tensioning procedure was completed for the final time on Earth in December 2020.

The James Webb Space Telescope’s final sunshield deployment and tensioning tests were completed in December 2020.

Credits: NASA/Chris Gunn

“Think of it backwards; we want the deployed sunshield to achieve a specific shape so we get the performance we need. The whole folding process was designed with that in mind. We have to fold cleanly and carefully the same way each time, to ensure the unfolding occurs exactly the way we want it,” said James Cooper, lead sunshield engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

For instance, one of the most intricate aspects of the folding process involved aligning the membrane stacks. Each of the sunshield’s layers has hundreds of intentional holes, which are deliberately arranged to avoid light and heat from passing to the optical elements of the telescope when the sunshield is fully deployed. These holes must be lined up during folding so that Webb technicians can insert “pins” through the holes in each membrane stack. The 107 “pins,” or membrane release devices, will help restrain the layers for launch, but release to unfold the sunshield once the telescope is in space.

“It’s a very methodical process that we use to make sure everything is aligned correctly,” said Marc Roth, mechanical engineering lead at Northrop Grumman. “Our team has been through multiple training cycles, and we’ve implemented many lessons learned from the previous times we’ve done this process, all culminating in this last sunshield fold.”

Over the next three months, engineers and technicians will finish stowing and securing the packed sunshield. This process will involve installing the membrane release devices, rigging and securing all of the sunshield cables, and stowing covers for the sunshield membranes. It will also include stowing the two “arms” of the sunshield — the Mid-Boom Assemblies — which will horizontally extend the sunshield outwards during deployment, as well as stowing the two pallet structures that hold the sunshield in place.

The James Webb Space Telescope previously deployed its primary mirror in March 2020. Its folded sunshield is also visible in this image.

Credits: Northrop Grumman

The observatory will additionally undergo a final mirror deployment before it is shipped to its launch site in French Guiana, South America.

The Webb engineering team continues to follow personal safety procedures in accordance with current Centers for Disease Control and Prevention and Occupational Safety and Health Administration guidance related to COVID-19, including mask-wearing and social distancing.

The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Astronauts move SpaceX capsule to new docking port for 1st time ahead of space station crew arrivals

NASA's SpaceX Crew-1 astronauts completed the first commercial crew port relocation at the International Space Station on Monday (April 5), as they moved the Crew Dragon spacecraft in preparation for the arrival of the next crew. The relocation was performed by NASA astronauts Michael Hopkins, Victor Glover and Shannon Walker, along with Japan Aerospace Exploration Agency (JAXA) astronaut Soichi Noguchi. The crew undocked the Crew Dragon, nicknamed Resilience, from the forward port of the space station's Harmony module at 6:30 a.m. EDT (1030 a.m. GMT) and reconnected to the module's space-facing port at 7:08 a.m. EDT (1108 GMT). The astronauts moved Resilience to a different port on the space station to make room for an incoming Crew Dragon spacecraft arriving later this month, named Endeavour, which will dock at Harmony's forward port. The arriving SpaceX Crew-2 mission includes NASA astronauts Shane Kimbrough and  Megan McArthur, JAXA astronaut Akihiko Hoshide, and European Space Agency (ESA) astronaut Thomas Pesquet. The crew is scheduled to launch to the space station on April 22 from Launch Complex 39A at NASA's Kennedy Space Center in Florida.

"We're very excited about [moving Resilience] and we'd like to say congratulations on behalf of the whole Expedition 64 team as well as the Crew-1 Dragon team. Congratulations to the commercial crew program for 10 years. What an amazing 10 years it has been," Hopkins said during a call with Steve Stich, NASA Commercial Crew Program manager, from the space station on Friday (April 2). "To think about where you started and where we are now — and now we're getting ready to actually take this vehicle out for a little spin. … We're all very excited to be a part of it."

On March 19, NASA astronaut Kate Rubins, along with two Russian cosmonauts Sergey Ryzhikov and Sergey Kud-Sverchkov, relocated the Soyuz MS-17 spacecraft from the Earth-facing port of the station's Rassvet module to the space-facing Poisk port. However, unlike the Soyuz relocation maneuver, which required manual flying, the Crew Dragon is operated autonomously.

"It's pretty cool and it is quite an amazing view to separate from your vehicle that's been your home for months and to be able to look at it from 60 meters [about 200 feet]," Rubins said during the call from the space station, which NASA shared on YouTube Friday (April 2).

In preparation for Monday's relocation, Hopkins said he would be spending his Easter Sunday making sure he cleaned everything out of the Crew Dragon spacecraft — his version of an Easter egg hunt, since he had been staying in Resilience for the last couple of months, he said during the call.

The spacecraft has been "largely quiescent" since the SpaceX Crew-1 astronauts arrived at the space station on Nov. 16. Therefore, the crew prepared for the move by verifying that Resilience's communication systems were up and running, and completing suit fit checks, which Hopkins said "went very well" during the call.

Crew-1 is scheduled to return to Earth in late April or early May, leaving the space-facing port of Harmony vacant for when a Dragon cargo spacecraft arrives with supplies and the first set of new solar arrays for the space station later this summer. Rubins and Glover began preparing the space station for the new solar arrays during a spacewalk on Feb. 28, when they installed one of two modification kits that are needed to support the new arrays. The Dragon cargo spacecraft will need to dock at the space-facing port to allow for robotic extraction of the new solar arrays from Dragon's trunk using Canadarm2, according to a statement from NASA.

While today's relocation maneuver was the first time a Crew Dragon spacecraft needed to be moved, it likely won't be the last, given the Crew-1 mission is the first of six certified crew missions NASA and SpaceX have planned as a part of the agency's Commercial Crew Program, according to the statement.

Lunar Reconnaissance Orbiter Spies Movement of Shadows Near the Moon’s South Pole

At the Moon’s North and South Poles, the Sun is never more than 1.5° above or below the horizon. The resulting pattern of daylight and shadows is unlike anywhere else on the Moon — or the Earth. After zooming in on a small lunar highland area near the South Pole, this visualization recreates the illumination conditions there over a period of two lunar days, equal to two months on Earth. This close to the pole, the Sun doesn’t rise and set. Instead, as the Moon rotates on its axis, the Sun skims the horizon, traveling a full 360 degrees around the terrain. Mountains as far as 75 miles (120 kilometers) away cast shadows across the landscape. With the Sun at such a low angle, it can never reach the floors of some deep craters. Places the Sun never reaches are known as permanently shadowed regions. They are the locations of some of the coldest spots in the solar system, and because of that, they trap volatile chemicals, including water ice, that would immediately sublimate (transform directly from a solid to a gas) in the harsh, airless sunshine that falls in most other places on the Moon.

The Sun appears to travel in a circle at the Earth’s poles, too, but it also travels through a range of altitudes. From spring equinox to summer solstice, for example, the Sun is climbing higher in the sky, reaching an altitude of 23.4°. It only hugs the horizon for a few days around the equinoxes. At the Moon’s poles, the Sun is always near the horizon, and the shadows are perpetually long, sweeping across the surface with the changing solar azimuth.