Solar flares are complex phenomena. They involve plasma, electromagnetic radiation across all wavelengths, activity in the Sun’s atmosphere layers, and particles travelling at near light speed. Spacecraft like NASA’s Solar and Heliophysics Observatory (SOHO) and the Parker Solar Probe shed new light on the Sun’s solar flares.
But it was a Japanese-led mission called Yohkoh that spotted an unusual solar flare in 1999. This flare displayed a downward flowing motion toward the Sun along with the normal outward flow. What caused it?
A team of researchers think they’ve figured it out.
When the 1999 Yuhkoh flare was spotted, astrophysicists wondered what caused the downward motion. They called these dark finger-like phenomena “downward-moving dark voids.” Astrophysicists have a more accurate term for them now: supra-arcade downflows (SADs.)
A solar arcade is an active area with multiple coronal loops. Coronal loops are magnetic structures that extend from the Sun’s photosphere out into the corona, looping back down to reconnect with the photosphere again. Coronal loops trap plasma magnetically, and that makes them visible.
This image is an example of solar coronal loops observed by the Transition Region And Coronal Explorer (TRACE). These loops have a temperature of approximately 106 K. These loops contrast significantly with the cool chromosphere below. Image Credit: By NASA Public Domain
A supra-arcade is a solar arcade with added features. Along with the loops, there are downflows above the arcade. Scientists thought supra-arcades are somehow connected with the magnetic reconnection behind solar flares, but the specifics were unknown.
“We wanted to know how these structures occur,” says lead author and CfA astronomer Chengcai Shen. “What’s driving them, and are they truly tied to magnetic reconnection?”
The Sun has complex magnetic fields that can become compressed and disfigured. They can break, releasing fast-moving and powerful radiation along magnetic lines, then reconnect to form loops.
“On the Sun, what happens is you have a lot of magnetic fields that are pointing in all different directions. Eventually, the magnetic fields are pushed together to the point where they reconfigure and release a lot of energy in the form of a solar flare,” says study co-author and CfA astronomer Kathy Reeves.
“It’s like stretching out a rubber band and snipping it in the middle. It’s stressed and stretched thin, so it’s going to snap back,” Reeves added.
That knowledge is firmly established, so it’s reasonable to conclude that the same mechanism guided SADs. “A characteristic feature of magnetic reconnection is the production of fast reconnection outflow jets near the plasma Alfven speeds,” the authors write in their paper. “In eruptive solar flares, dark, finger-shaped plasma
downflows moving toward the flare arcade have been commonly regarded as the principal
observational evidence for such reconnection-driven outflows.”
But observations didn’t entirely back that explanation. It comes down to speed.
“However, they often show a speed much slower than that expected in reconnection theories, challenging the reconnection-driven energy release scenario in standard flare models,” they write.
In the elastic band analogy, the snap-back is rapid. But when scientists watched these SADs, most of them didn’t snap back. Instead, they reconnected more slowly with the Sun. If the same thing happened with an elastic band, we’d think somebody spiked our drink.
“This is not predicted by classic reconnection models, which show the downflows should be much quicker. It’s a conflict that requires some other explanation,” lead author Shen said.
Here’s where NASA’s Solar Dynamics Observatory (SDO) comes in. NASA launched the SDO in 2010 to study the nature of the Sun-Earth system and how it affects life on Earth. One of the SDO’s instruments is the Atmospheric Imaging Assembly (AIA.) The AIA gives us continuous full-disk coverage of the Sun’s chromosphere and corona.
This image from the SDO’s AIA is an excellent example of the instrument’s power. It’s an extreme UV light image of the magnetic fields and the loops they create, which are invisible to our eyes. These features dwarf the Earth. Image Credit: Solar Dynamics Observatory/NASA.
Shen and the other authors created 3D simulations of solar flares and compared them to solar flares the SDO observed. They found that magnetic reconnection isn’t the source of SADs.
Instead, fluid dynamics are at the heart of SADs. Two fluids of different densities create the SADs when they interact in the turbulent environment above the arcade.
This image shows some of the simulations created by the team of researchers. It shows how the density of the plasmas changes over time, leading to the development of SADs. Image Credit: Shen et al. 2022.
The authors say that the turbulent environment in this “interface region” where downward reconnection outflows impinge on closed flare arcades hasn’t received much attention in previous research. “This interface region hosts a myriad of turbulent flows, electron currents, and shocks, crucial for flare energy release and particle acceleration,” the authors explain in their paper. They liken it to another astrophysical phenomenon, “… the highly turbulent region sandwiched between the forward and reverse shock in supernova remnants,” they write. Plasma in that region of a supernova also forms finger-like structures.
This is the Crab Nebula, a well-studied supernova remnant. It illustrates the turbulent flows and shock waves that create the same structures seen in SADs. The fingers in remnants like these are Rayleigh-Taylor fingers. The unstable interface between fluids of different densities creates the fingers, similar to how SADs are formed on the Sun. Image Credit: By NASA, ESA, J. Hester and A. Loll (Arizona State University) Public Domain
In this case, the two fluids are both plasmas. But they have different densities, leading to the unexplained behaviour of SADs.
“Those dark, finger-like voids are actually an absence of plasma. The density is much lower there than the surrounding plasma,” co-author Reeves explained.
The authors intend to keep studying SADs and other solar features using observations and simulations. They think their work might lead to better tools for predicting space weather.
The year 2021 was a big one as far as stories from space are concerned! From start to finish, 2021 witnessed innumerable milestones and groundbreaking missions mounted by space agencies and the commercial space industry. Among them, the long-awaited launch of the James Webb Space Telescope, the arrival of the Perseverance mission, the launch of Double-Asteroid Redirect Test (DART), multiple test flights with the Starship, and the inauguration of space tourism. There was something for everyone!
However, looking at what’s planned for the year ahead, one might get the impression that 2021 was the appetizer and 2022 is the main course! That may sound like an idle boast, but not when you consider all of the ambitious missions, programs, and developments that are scheduled and anticipated for the next twelve months! So exactly what’s in store for space in 2022? We’ve provided a helpful list below:
Ariane 6
Building on their success with the Ariane 5 heavy launch vehicle, the European Space Agency and their primary contractor (Arianespace) plan to unveil its successor in 2022. The Ariane 6, which has been in development since 2010, is a two-stage heavy launch vehicle that measures over 60 meters (197 ft) tall and will weigh up to 900 metric tons (992 US tons) with a full payload.
Artist’s view of the configuration of Ariane 6 using four boosters (A64). Credit: ESA
Depending on the payload, the rocket will come in two variants: the Ariane 62, with two strap-on boosters, and the Ariane, 64 with four. The Ariane 62 will be capable of launching payloads of approx. 4500 kg (9920 lbs) into a geostationary transfer orbit (GTO) or 10,300 kg (22,700 lbs) into a Low Earth orbit. (LEO). The Ariane 64 will be able to launch payloads of approx. 11,500 kg (25,350 lbs) to GTO and 20,600 kg (45,415 lbs) into low Earth orbit.
Led by ArianeGroup, 600 companies in 13 European countries have been involved in the development of the Ariane 6. Meanwhile, France’s space agency (CNES) is busy preparing the Ariane 6 launch facilities at Europe’s Spaceport at Kourou, French Guiana. The ESA hopes to conduct the first flight of the Ariane 6 during the second quarter (between April and June) of 2022.
DART
The NASA Double Asteroid Redirection Test (DART) mission is a demonstrator that will evaluate planetary-defense technologies. DART will test the kinetic impact technique, where a spacecraft intentionally collides with a potentially-hazardous asteroid to change its course and divert it from hitting Earth. The target for this mission is the binary near-Earth asteroid (65804) Didymos, which consists of a primary measuring 780-meter (2,560 ft) and a small “moonlet” 160-meters (525 ft) in size.
While this asteroid does not pose a threat to Earth, it is an ideal testing ground to evaluate the technology and technique involved. Once the DART spacecraft reaches Didymos, it will rely on an onboard camera (named DRACO) and sophisticated autonomous navigation software to collide with the moonlet at a speed of approximately 6.6 km/s (4 mi/s). The collision will cause a change in the speed of the moonlet’s orbit, which telescopes on Earth will then measure.
Illustration of the DART spacecraft with the Roll-Out Solar Arrays (ROSA) extended. Credit: NASA
On December 25th, 2021, fans of astronomy and cosmology received what was arguably the best Christmas present possible! After years of delays, cost overruns, and additional testing, the James Webb Space Telescope finally launched to space. In the early weeks of January, NASA provided a regular stream of updates, keeping the world appraised of the telescope’s successful pre-mission deployments. This included the extension of its heat shield, secondary mirror, primary mirror, and other crucial mission hardware.
Once operational, Webb will address some of the most fundamental questions about astronomy, physics, and the origins and evolution of the Universe. This will include observing the first stars that formed 200 – 400 million years after the Big Bang, followed by the first galaxies and how they evolved. These observations will allow astronomers to measure the influence of Dark Matter and Dark Energy in cosmic evolution.
Webb’s advanced infrared imaging will allow it to observe star systems that are still in the process of forming, which will answer unresolved questions about how stars seed the Universe with building materials to make planets and how planets can give rise to life. It will also greatly expand the census of extrasolar planets and help to characterize their atmospheres, allowing astronomers to determine which planets are truly “habitable.”
At present, the JWST is busy testing the individual segments of its primary mirror, a process that is expected to last for another week (January 22nd). On the following day, the James Webb will conduct its L2-Insertion Burn, a course correction that will place it into the L2 Lagrange Point, where it will stay for the duration of its ten-year mission. By this summer, six months after launch, Webb will be collecting its first light and should have some stunning first images for the public!
Juno
In August 2011, NASA’s Juno probe launched from Cape Canaveral Air Force Station (since renamed Cape Canaveral Space Force Station.) By July 2016, it established orbit around Jupiter and became the second mission dedicated to studying Jupiter’s atmosphere, composition, magnetic field, and gravitational field. Starting in September 2022, during its 45th polar orbit of Jupiter (perijove 45), it will shorten its orbit from 43 to 38 days. This will allow it to conduct multiple flybys of Europa.
The data Juno obtains about Jupiter’s largest moons (Callisto, Ganymede, Europa, and Io) will help inform future missions to study these satellites. For example, the ESA’s JUpiter ICy moons Explorer (JUICE) will launch in 2023 and arrive at Jupiter by 2031. By 2032, it will assume orbit around Ganymede to conduct surveys of the surface, followed by a series of flybys of Europa. There’s also NASA’s Europa Clipper Mission, which is scheduled to launch in 2024 and arrive at Jupiter by 2030.
These two missions will examine Jupiter’s moons to learn more about the composition of their surface ice, investigate water plume activity, learn more about their interior oceans, and scan for potential biosignatures. The data they obtain will also inform future missions to Jupiter’s icy moons, like the Europa Lander.
NASA has extended the mission of its Juno spacecraft exploring Jupiter. The extended mission involves 42 additional orbits. Credit: NASA/JPL-Caltech/SwRI
New Glenn
Blue Origin made some significant strides in 2021 with their New Shepard reusable launch vehicle. After a series of uncrewed test flights, including one loaded with science experiments and a “crew rehearsal,” the company conducted three high-profile flights to the edge of space with at least one celebrity aboard. On the inaugural flight, the crew included Jeff Bezos, his brother Mark, commercial astronaut Wally Funk, and 18-year old physics student Oliver Daemen, the oldest and youngest people to go to space (respectively).
On the second flight, famed actor William Shatner was the headliner, with Laura Shepard Churchley (Alan Shepard’s daughter) and two-time Superbowl Champion and Good Morning America co-anchor Michael Strahan headlining the third. In 2022, Blue Origin is expected to press on with developing their New Glenn launch vehicle, a two-stage reusable launch vehicle named in honor of astronaut John Glenn. If all goes well, they may attempt the first launch sometime between October and December 2022.
Work on the rocket’s design began in 2012, and the first detailed specifications were unveiled in September 2016. While Bezos’ hoped that the rocket would be ready in time for a 2020 launch, by February 2021, the company announced that the target launch date would be “no earlier than the fourth quarter of 2022.” Once complete, the New Glenn will measure over 98 m (322 ft) tall, slightly less than the 110.6 m (363 ft) Saturn V launch vehicle that flew the Apollo astronauts to the Moon.
With its massive 7 meter-wide (22 ft) fairing, seven BE-4 primary engines, and three BE-3U secondary engines, the rocket will be able to lift 45 metric tons (49.6 U.S. tons) to Low Earth Orbit (LEO) and the 13 metric tons (14.33 U.S. tons) to a Geostationary Transfer Orbit (GTO). The ability to conduct orbital launches with these types of payloads means that Blue Origin will finally be competitive with other launch providers, like SpaceX and United Launch Alliance (ULA).
Artist’s impression of the New Glenn rocket. Credit: Blue Origin
Psyche
This will be the first mission to explore a metallic (M-type) asteroid, but the significance of this mission goes far beyond this. Psyche II is believed to be the core remnant of a protoplanet that formed in the early Solar System and experienced a massive impact that removed its outer layers. As a result, only the protoplanet’s iron-nickel core was behind as the largest known M-type asteroid in the Solar System. In addition to these metals, the mission team also anticipates that there will be large quantities of gold, platinum, and other precious metals.
Some estimates place the value of this metallic body at $10 quintillion (10 x 1018), which is significantly more than the entire global economy – over $80 trillion annually. (World Bank, 2017). However, the true value in this asteroid (for the time being) lies in the scientific returns it promises. By studying this planetoid remnant, astronomers expect to learn a great deal about the early Solar System, its formation, and evolution.
The Psyche mission will launch on August 1st, 2022, and will arrive around Psyche by January 31st, 2026.
Rosalind Franklin Rover (ExoMars 2022)
This year, the ESA will send the second installment in their ExoMars program to Mars. This will consist of the Roscosmos-designed Kazachok Lander and the ESA-designed Rosalind Franklin Rover. Building on the work of its predecessors, the ExoMars 2016 mission (which consisted of the Trace Gas Orbiter and Schiaparelli Lander), Kazachok and Rosalind Franklin will study the Martian surface to determine if life ever existed on Mars (and could today).
This mission is scheduled to launch between August and October of 2022 from the Baikonur Cosmodrome in Kazakhstan and land on Mars roughly nine months later. Once there, the rover will join its peers, like the Curiosity and Perseverance rovers, in the ongoing search for potential biosignatures. These could indicate the existence of life on Mars billions of years ago when the planet had a thicker atmosphere and still had flowing water on its surface.
Space Launch System (SLS)
As NASA’s next-generation super-heavy launch vehicle, the Space Launch System (SLS) is the successor to the Saturn V rocket that transported the Apollo astronauts to the Moon. Development began on the rocket in 2011 and has endured multiple delays and cost overruns since. However, NASA made significant strides towards getting the SLS ready in 2020 and 2021. This included the completion of the Green Run with the Core Stage of the rocket, an 8-step evaluation that culminated with the “Hot Fire Test” in March of 2021.
Since then, the Core Stage has been moved to NASA’s Launch Control Center (LCC) at the Kennedy Space Center in Florida, where it was integrated with its solid rocket boosters and stacked with the Orion Spacecraft. While NASA was hoping to conduct the inaugural launch of the SLS with an Orion spacecraft (Artemis I) by November 2021, that flight is now scheduled to launch by March 20th, 2022.
As part of the Artemis Program, this flight will see an uncrewed Orion sent on a circumlunar flight that will last 25 days. This mission will gauge the performance of both systems and allow mission scientists to develop vital experience in preparation for crewed flights. This will include Artemis II, a crewed mission that will launch in May 2024 that will see four astronauts conduct a lunar flyby before returning to Earth.
The fully-stacked SLS at the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida. Credit: NASA
If all goes well, Artemis III, the first crewed mission to the lunar surface since the Apollo Era, will occur sometime in 2025. This mission will consist of a crew of four flying to the Moon, and two astronauts (“The first woman and first person of color“) will land on the surface using a Human Landing System (SLS). This will be followed by several more crewed missions that will establish permanent infrastructure on the surface and in orbit – including the Artemis Base Camp and the Lunar Gateway.
In addition to the Artemis Program, the SLS is also an essential component for NASA’s long-term vision of crewed missions to Mars (their previous “Moon to Mars” mission architecture). These missions are still expected to occur early in the next decade, coinciding with launch windows of 2033, 2035, 2037 – i.e., every twenty-six months when Earth and Mars are at the closest point in their orbits to each other (aka. a “Mars Opposition“).
Starship
SpaceX will also be blazing a trail this year with the first orbital flight test of the Starship and Super Heavy launch vehicle. Development on this spacecraft officially began after Musk unveiled the Interplanetary Transport System (ITS) in 2016 – though concepts for a “Mars Colonial Transporter” (MCT) and “BFR” were discussed as early as 2005. In 2017, Musk shared a detailed mission architecture and a timeline for using the ITS to establish a permanent human outpost on Mars.
By 2018, the ship’s design and the mission architecture were updated, and the launch system was renamed again – the Starship orbital spacecraft and Super Heavy booster. Shortly after that, SpaceX expedited construction of its South Texas Launch Facility, located near the town of Boca Chica on the Gulf of Mexico. This is where, for the past three years, SpaceX has progressively tested and validated the Starship through test firings, pressure tests, and test flights.
The Starship and Superheavy (fully stacked) standing next to the “Mechazilla” launch and retrieval tower at Boca Chica, Texas. Credit: SpaceX
In 2021, SpaceX accomplished several milestones with the development of the Starship and the Boca Chica facility (now called the Starbase). After a series of successful flight and glide tests with Starship prototypes (two even managed to stick the landing!), SpaceX built a prototype for orbital flight (SN20) with six Raptor engines and heat shielding. They’ve also finished assembling multiple Super Heavy prototypes and built the “Mechazilla” launch and retrieval tower.
Though SpaceX had indicated that it hoped to conduct the first orbital flight test in early 2022 (January or February), the Federal Aviation Administration (FAA) indicated on December 28th that this must wait upon the completion of their Programmatic Environmental Assessment (PEA) – which they are aiming to finish by February 28th. This means that SpaceX will likely have to wait until the end of the first quarter (or early Q2) to make their orbital launch test.
Based on the flight path SpaceX’s previously filed with the Federal Aviation Administration and a recent announcement by NASA, the flight will launch either from the Starbase or the newly-commissioned Launch Complex 49 at Cape Canaveral, Florida.
Tiangong
This year will also see significant developments for the China National Space Agency (CNSA). For instance, China’s plans to complete its Tiangong space station (“Heavenly Palace”) in orbit, which is intended to rival (and possibly succeed) the International Space Station (ISS). This will be the culmination of the Tiangong program and will build on the experience gained from the Tiangong-1 and Tiangong-2 space stations.
The Tianhe module will form the core of the space station, with other modules to be added later to increase the size of the station and make more experiments possible. Credit: Saggitarius A/Wikimedia Commons
Deployment of the Tiangong space station began with the launch of the Tianhe core module on April 29th, 2021. This year, the two other primary modules will be launched to orbit, where they will be integrated with the core module. This includes the Wentian Laboratory Cabin Module (“Quest for the Heavens”) and the Mengtian Laboratory Cabin Module (“Dreaming of the Heavens”) – which are scheduled to launch between May and June 2022 and August and September 2022 (respectively).
The CNSA also plans to conduct multiple launches to the Tiangong space station this year, including two Shenzhou crewed missions and two Tianzhou cargo missions.
ULA Vulcan Centaur
Since 2014, the United Launch Alliance (ULA) has been working on a new heavy launch system known as the Vulcan Centaur. This two-stage rocket will consist of a first stage that relies on a single Blue Origin BE-4 engine and up to six GEM-63XL solid rocket boosters (SRBs). The second stage consists of the ULA’s new Centaur V vehicle powered by two Aerojet Rocketdyne RL-10 engines.
Since work began on the Vulcan Centaur, the ULA has indicated that they intend to upgrade the rocket to make it at least “partially reusable.” This included early plans to make the first stage BE-4 engines reusable by making them detachable and equipping them with parachutes. A more bold concept, Sensible Modular Autonomous Return Technology (SMART), consisted of making the first-stage booster engines, avionics, and thrust structure into a single module that would be detachable and retrievable.
After the first stage completed its booster engine burn, this module would detach from the propellant tanks and undergo mid-air retrieval with the help of parachutes and an inflatable heat shield. While there’s been no development on this front, the ULA did indicate in late 2019 that they still planned on making the Vulcan’s first-stage BE-4 engines detachable and reusable.
Vulcan Centaur, United Launch Alliance’s next-generation American rocket, lifts off in this artist’s rendering. Credit: ULA
While ULA had intended to conduct the maiden flight in 2021, the date has since been pushed to 2022 due to delays with the development of the commercial payload, which were a result of the pandemic. For this flight, the Vulcan Centaur will launch Atrobotic Technology’s Peregrine Lunar Lander (Peregrine Mission-1) as part of NASA’s Commercial Lunar Payload Services (CLPS) program.
Vera Rubin Observatory
In addition to the many missions destined for space, the Moon, and Mars, many developments are expected to happen here on Earth this year as well. One of them is the Vera C. Rubin Observatory, formerly known as the Large Synoptic Survey Telescope (LSST), which is scheduled to gather its first light by October 2022. Full-survey operations are not expected until October 2023 due to COVID-related schedule delays. However, its main astronomical survey – the Legacy Survey of Space and Time (LSST) – will be worth the wait!
Using its massive 3200-Megapixel camera, the LSST will consist of four major science goals. These include probing the Universe’s large-scale structure to measure the influence of Dark Matter and Dark Energy, taking an inventory of objects in the Solar System, exploring the transient optical sky, and mapping out the Milky Way Galaxy. In addition, the Observatory will be invaluable to the study of interstellar objects (ISO) and is expected to detect between five objects a year or a few a month.
Rubin Observatory at sunset, lit by a full moon. Credit: Rubin Observatory/NSF/AURA
While many predict that 2022 will have its share of tribulations, not the least of which is because of the ongoing pandemic, it’s also clear that it will be an exciting time characterized by multiple breakthroughs and important milestones. Perhaps the milestones and discoveries that we make in space this year will remind us that there are always reasons to be hopeful. A few gentle reminders of our place in the Universe has a way of putting things into perspective!
Should we thank our well-behaved Sun for our comfy home on Earth?
Some stars behave poorly. They’re unruly and emit powerful stellar flares that can devastate life on any planets within range of those flares. New research into stellar flares on other stars makes our Sun seem downright quiescent.
NASA’s TESS (Transiting Exoplanet Survey Satellite) is a planet hunter. Its primary task is to watch stars for any regular dips in light. Those dips can signal the presence of a planet as it passes between us and the star. TESS is very successful at finding planets.
But TESS does more than identify exoplanet candidates. TESS’s keen-eyed cameras reveal a lot about the stars the planets are orbiting. One of the mission’s objectives is to study about 1,000 M-dwarf (red dwarf) stars closest to us. Red dwarfs are the most plentiful stars in our galaxy, so most exoplanets are probably orbiting red dwarfs. About 75% of the stars in the Milky Way are M-dwarfs and many of them host planets in their habitable zones.
But red dwarfs are complicated stars. On the one hand, they’re the longest-lived stars, so planets orbiting them can count on stable conditions for a long time. That long-lived stability is good for the development of life.
On the other hand, red dwarfs can emit powerful flares. Stellar flares can be hard on planets and can severely limit the possibility of life on planets around red dwarfs.
“Many of these red dwarf stars can emit flares 1,000 times larger than those from the Sun…”
Ward Howard, lead author, U of C Boulder.
This is an artist’s conception of a violent stellar flare erupting on the red dwarf Proxima Centauri, our nearest neighbour. Our Sun seems relatively calm compared to red dwarfs. Credit: NRAO/S. Dagnello.
This puts planet-hunting in a new light. Planet hunting’s over-arching goal is finding planets in a star’s habitable zone where liquid water could exist on the surface. But our growing knowledge of flaring may make our understanding of habitable zones outdated.
The study is the first large-scale analysis of stellar flaring. It’s based on data collected at 20-second intervals, a rapid cadence for observations. The faster cadence gathers more granular data.
Our Sun emits flares, which can disrupt electronic systems on Earth and in satellites. The Sun is nothing compared to the stars in this study, even though red dwarfs are smaller than the Sun.
“The sun is very well behaved,” lead author Howard said in a press release. “Many of these red dwarf stars can emit flares 1,000 times larger than those from the Sun, and you can only imagine what that might do to a planet or to life on the surface.”
TESS is in its extended mission now. The 20-second observation intervals are more rapid than the two-minute intervals used in TESS’s primary mission. The rapid intervals give astrophysicists a better window into flares. They can watch as flares develop and measure the radiation more accurately. Howard and MacGregor discovered that flares are more complicated than thought, and some can burst multiple times.
“They have all sorts of weird structure in the light curves, which indicates that some of them are bursting multiple times,” co-author MacGregor said.
This figure from the study shows the difference between 20-second intervals and 2-minute intervals. The left panel shows both intervals binned to 2-minute intervals. The right panel shows how the 20-second cadence reveals more detail in the flares. Image Credit: Ward and MacGregor 2022.
“The new 20-second cadence mode reveals significant substructure in large flares that would have been missed
at 2 min cadence,” the authors write in their paper. “Higher-cadence observations also remove degeneracy present at 2 min cadence between significantly different flare morphologies,” they say when discussing the above figure.
“We have historically had a very simple picture of stellar activity, where one loop breaks and we have one outburst of energy, and then it slowly dies away, and then we think about the frequency of that,” MacGregor continued. “That’s the model that’s been fed into everything we think about stars and their impact on planets, and it’s clearly just flat-out wrong.”
“It allows us to kind of have a statistical understanding of how often do certain things occur,” Howard said, adding that scientists have never before been able to determine how much radiation reaches planets during the peak of the superflares and how much complexity the flares have.
Astrophysicists describe stellar flares in two phases: the rise phase between the beginning of the flare and peak brightness and the decay phase. “Many large flares exhibit complex substructure during the rise phase,” the authors write, and the 20-second cadence helps reveal the complexity, while the slower cadence doesn’t. “We find 46% of the large flares in our sample exhibit complex structure in the rise phase (201 out of 440 flares), making this a common phenomenon at the 20-second cadence.”
This figure shows the rise phases of ten of the flares in the study—nearly half of the flares show complex substructures during the rise phase. Although exceptions exist, a greater degree of complexity generally correlates with longer rise times. Resolving the complex substructure in the rise phases of large M-dwarf flares is more difficult in lower-cadence observations. Image Credit: Ward and MacGregor 2022.
The study also found other flare morphologies that the authors describe as unusual yet frequently-occurring. One is the peak-bump flare. This type of flare has an initial highly-impulsive peak followed by a less-impulsive second peak. About 17% of the flares exhibit this morphology.
Another unusual type is the flat-top flare. Most flares have a very powerful impulsive peak, but flat-top flares have more constant emission levels at their peak. Previous studies show that these flat-top flares can peak for almost one hour, though the longest-lasting peak in this study was 26 minutes. 24 of the flares in this study—about 5%—are flat-top flares.
This figure from the study shows eight flat-top flares. The 20-second cadence observations helped identify these types of flares. Image Credit: Ward and MacGregor 2022.
Red dwarfs flare differently than our Sun. But the basics are the same. All stars have powerful magnetic fields, and sometimes those fields become entangled. The entanglement spawns powerful bursts of radiation and charged particles. The result is beautiful, looping, solar prominences. Prominences remain anchored to the Sun but extend thousands of kilometres into space.
“Our sun does this, and we can get beautiful images where you see these loops of emission protruding out of the surface of the sun, and then they break and stream out into space,” MacGregor said.
This is a solar eruptive prominence seen in extreme UV light on March 30, 2010, with Earth superimposed for a sense of scale. Credit: NASA/SDO
When a solar prominence breaks free from the Sun, it’s a flare. Most flares are accompanied by coronal mass ejections (CME), masses of solar plasma and magnetic fields. When the Sun emits a CME toward Earth and strikes our planet’s magnetosphere, we get beautiful light shows: the aurorae. We also get geomagnetic storms, and if they’re powerful enough, they can damage electrical grids and satellites. But that’s rare.
“So we see beautiful lovely green lights,” MacGregor said. “What we’re actually observing is the effect of our sun splitting apart molecules in our atmosphere and then the release of energy from that splitting of things like ozone and water.”
Things play out differently on red dwarfs.
Red dwarfs are smaller than stars like our Sun. But they can rotate more rapidly than larger stars, so they can have more powerful magnetic fields. This creates more powerful flares, and sometimes what astrophysicists call superflares. Superflares can be up to 30 times more powerful than our Sun’s flares—maybe even more potent than that.
That much energy can shred a planet’s atmosphere. Most planets orbiting in a red dwarf’s habitable zone are likely tidally locked. This paints an ugly picture for life. One side of a world would be regularly blasted by powerful flares, while the other remained dark. Could life survive there?
Maybe it could. Some evidence shows that red dwarfs emit their flares from higher latitudes and poles. But planets orbit their stars in the ecliptic, which might spare them from the worst effects.
This figure is from a 2021 study showing that red dwarfs emit flares from their polar regions. The black star marks the star’s pole. The red circle shows the flare latitude, and the red dot marks the active flaring. The yellow dashed line marks the maximum typical solar flare latitude. Planets orbiting in these stars’ ecliptics likely escape the worst effects of powerful flares. Image Credit: Ilin et al. 2021.
There are no firm measurements of how much radiation from red dwarf flares would reach any planets around the stars. The authors discuss this in their paper but can’t reach solid conclusions. Scientists work with a survival concept called D90—the UV dose needed to kill 90% of a hardy bacterium called D. Radiodurans. The authors find that “… 1/3 of our 1034 erg flares reach this limit during the 20-second peak epoch.” They also found that none of the flares were powerful enough to kill 100% of D. Radiodurans.
These numbers are preliminary, and there are assumptions behind them. The hypothetical planets subjected to the flares are unmagnetized and have no significant atmospheres. Magnetospheres of differing strengths and different types of atmospheres could strongly affect how much UV radiation from flares would reach a planet’s surface.
Our understanding of red dwarfs and their flaring is in the early stages. This study removes some guessing and conjecture and replaces it with some of our most detailed knowledge of flaring yet.
“It allows us to kind of have a statistical understanding of how often do certain things occur,” Howard said, adding that scientists have never before been able to determine how much radiation reaches planets during the peak of the superflares and how much complexity the flares have.
It doesn’t paint a pretty picture, though.
These results put our own neighbourly Sun in a pretty good light. The Sun’s flares are relatively calm and gentle compared to some powerful bursts from red dwarfs.
Complex life on Earth is only possible because of many variables that turned out just right. It looks like we can add the Sun’s relatively quiescent flaring to the list.
In the grand scheme of things, the structure of a black hole is pretty simple. All you need to know is its mass, electric charge, and rotation, and you know what the structure of space and time around the black hole must be. But if you have two black holes orbiting each other, then things get really complicated. Unlike a single black hole, for which there is an exact solution to Einstein’s equations, there is no exact solution for two black holes. It’s similar to the three-body problem in Newtonian gravity. But that doesn’t mean astronomers can’t figure things out, as a couple of recent studies show.
Although Einstein’s equations don’t have an exact solution for a binary black hole system, there are aspects of binary black holes that the equations predict. One of these is known as spin-orbit resonance. When a black hole rotates, the structure of space around it is twisted in the direction of rotation, known as frame dragging. When two black holes orbit each other closely, the frame-dragging of each black hole affects the rotation of the other. As a result, the two black holes will tend to enter a resonance, where the rotations either align in the same way (parallel) or opposite (anti-parallel). If spin-orbit resonance is real, then binary pairs should tend to have one of these orientations.
One recent study suggests this is true. In it, the team looked at gravitational-wave data from known black hole mergers, and found that their rotations tend to be parallel or anti-parallel. Given the small sample size, and the fact that black hole binary rotations are never exactly aligned, there isn’t enough data to confirm the effect, but the data we have points in that direction.
A simulation showing how black hole rotation can affect an orbiting body. Credit: Simon Tyran, via Wikipedia
One of the challenges to measuring black hole spin is that the signal is rather weak. The gravitational waves we measure from distant black hole mergers are so faint that it’s easy to get lost in the noise. Observatories such as LIGO and Virgo need to make extremely sensitive measurements, and their data must be filtered through computer models. Its the combination of data processing and computer simulation that makes the mergers detectable. Adding spin to the mix makes things even more difficult.
But in a second paper, the team looked at how we could get better results. They found that the signal for spin resonance is strongest when they are just about ready to merge. That makes sense since that’s when they are closest together and when frame-dragging is strongest. But currently, the rotation information for binary black holes is found by looking at gravitational waves while they are still orbiting each other. The team showed how models can analyze the near-merger signal instead, getting much better results. By applying this new method to black hole mergers, they should be able to confirm spin-orbit resonance in the near future.
Gravitational-wave astronomy is still a new field, and we’re still learning how to capture and analyze the data. As these new studies show, gravitational waves hold a great deal of information, and with a bit of digging there’s plenty more we can uncover.
The past month has been an exciting time for the James Webb Space Telescope! After launching on Christmas Day, the telescope spent the next few weeks deploying its mirrors, checking the individual segments, and then maneuvering to L2, where it will spend the next ten to twenty years unlocking the mysteries of the cosmos. According to NASA Administrator Bill Nelson, the Chief Science Communications Officer (CSCO) for the JWST and the Hubble Space Telescope (HST) for the ESA, James Webb will begin collecting light this summer.
To mark the occasion, the Virtual Telescope Project (VTP) captured images of James Webb to give people a sense of what it looks like in orbit. Unfortunately, there’s not a lot to see there, other than a bright dot in the night sky. But like Carl Sagan’s famous “Pale Blue Dot” picture of Earth (taken by Voyager 1 on its way out of the Solar System), or Cassini’s “The Day Earth Smiled” image, there’s a tremendous amount of significance in that small point of light.
The James Webb Telescope imaged from Earth. – January 24th, 2022. Credit: TVTP 2.0
The image of the JWST (shown above) was taken on January 24th using Elena. This robotic telescope tracked the apparent motion of the JWST automatically and acquired a single 300-single unfiltered exposure that shows the telescope’s position (indicated by an arrow in the center). When it was imaged, the JWST had reached its final destination (L2), placing it at a distance of about 1.4 million km (869,920 mi) from Earth.
In addition to the above image, the VTP also created a short GIF animation (below) that shows the JWST’s apparent motion against the stars. While it may look like little more than a tiny dot against a background of brighter dots (and the darkness of space), these images tell a story of an ambitious mission that was decades in the making. Work began on the telescope in 1996, and it was initially hoped that the James Webb would be launched by 2007 and with a budget of $500 million.
Unfortunately, there were many delays and cost overruns due to a major redesign, issues with the sunshield, and the Ariane 5 rocket that would launch it. The COVID-19 pandemic also imposed delays, as did the fact that the James Webb is the most complex and advanced space telescope ever conceived. Time and again, the origami-like nature of the telescope (where it has to fold up to fit within a payload fairing) required extensive testing runs, and the slightest issues required retesting and safety checks.
By 2016, construction was finally finished, but an extensive testing program still had to be completed. By late 2021, the telescope testing finished up, and the James Webb was shipped to Kourou, French Guiana, for integration with the Ariane 5 rocket. When the launch finally happened on Christmas Day, it went off without a hitch. Thomas Zurbuchen, NASA’s associate administrator for science missions, commented, “It’s truly Christmas with all the presents and everything and we have a space mission!”
The James Webb Space Telescope in motion against the stars. January 24th, 2022. Credit: TVTP 2.0
By 2016, construction was finally finished, but an extensive testing program still had to be completed. By late 2021, the telescope testing finished up, and the James Webb was shipped to Kourou, French Guiana, for integration with the Ariane 5 rocket. When the launch finally happened on Christmas Day, it went off without a hitch. NASA’s associate administrator for science missions Thomas Zurbuchen, “It’s truly Christmas with all the presents and everything and we have a space mission.”
Now that the mission is at L2, the mission team is waiting for the telescope to reach operational temperature. This will be followed by the activation of the telescope’s instruments, final testing, and calibration. Barring any issues, NASA anticipates that the James Webb will begin collecting its first light by June 2022. As NASA Administrator Bill Nelson said:
“Webb, welcome home! Congratulations to the team for all of their hard work ensuring Webb’s safe arrival at L2 today. We’re one step closer to uncovering the mysteries of the universe. And I can’t wait to see Webb’s first new views of the universe this summer!”
Just 4,000 light-years from Earth is a strange, star-sized object. It’s been observed by radio telescopes, but astronomers aren’t sure what it is. They call it a long period transient.
Transients are objects in the sky that change over some period of time. Fast transients are things such as pulsars, which emit a bright flash over a period of seconds or milliseconds. Slow transients are objects such as supernovae, which grow to extreme brightness over days or months. This new object is transient three times an hour. About every 18 minutes, it becomes one of the brightest radio objects in the sky, with its flash lasting anywhere from half a second to nearly a minute. Its long period and extreme brightness are what makes it so unusual.
One idea is that the object is a hypothetical object known as an ultra-long period magnetar. Magnetars are neutron stars, the same as pulsars, but magnetars have much stronger magnetic fields. Most magnetars are thought to rotate as quickly as pulsars, but their strong magnetic fields could interact with surrounding ionized gas in a way that causes it to slow down significantly. This would turn it into a kind of slow rotating pulsar. The problem with this idea is that astronomers have thought ultra-long period magnetars wouldn’t be nearly so bright. Another idea is that the object is a strange type of white dwarf, but it isn’t clear how a white dwarf could become so radio bright.
An artist view of the object as a magnetar. Credit: ICRAR
Based on observations, we do know the object has an intense magnetic field. The radio light we see from the object is highly polarized. Charged particles emit highly polarized light when they interact with a strong magnetic field. We also know the transient can’t simply be a standard pulsar effect. Pulsars emit regular flashes because their rotation sweeps a beam of intense radio light across the sky. We see a radio flash every time the beam sweeps our way, similar to the flash of a lighthouse. This object would flash about every 18 minutes, but these flashes would only happen over the course of a few hours. The team saw the object shift between active and quiet periods during their observation runs. So some strange happenings are going on.
Of course, the most exciting idea is that the transient object is something we don’t expect. Perhaps a newly formed black hole, or a hypothetical quark star. With only one example, it’s difficult to narrow down the possibilities. So the team is searching for similar objects in order to solve the mystery they never expected to find.
Is this a closeup look at a tree stump, or an orbital view of an impact crater? At first glance, it might be hard to tell. But this image of a crater on Mars provides planetary scientists almost the same kind of climate history data about the Red Planet as tree rings provide to climate scientists here on Earth.
This picture was taken by the Colour and Stereo Surface Imaging (CaSSIS) camera onboard the ESA/Roscosmos ExoMars Trace Gas Orbiter (TGO), which arrived at Mars in 2016 and began its full science mission in 2018.
This unnamed crater is located in the vast northern plains of Acidalia Planitia. This plain is north of Valles Marineris, and the region contains the famous Cydonia region (where the “Face on Mars” butte is (it aoesn’t actually look like a face), and well as heavily cratered highland terrain.
So, why does this crater look so unusual? Scientist from the ExoMars mission say the interior of the crater is likely composed of ice-rich material, and the quasi-circular and polygonal patterns of fractures could be the result of seasonal changes in temperature that cause cycles of expansion and contraction of those materials, eventually leading to the development of fractures.
Along the crater rim on the left, possible gullies are also visible.
An unusual crater on Mars, as seen by the CaSSIS camera onboard the ESA/Roscosmos ExoMars Trace Gas Orbiter (TGO) on 13 June 2021 in the vast northern plains of Acidalia Planitia. Credit: ESA/Roscosmos/CaSSIS.
Any water-ice rich soil would have been laid down during an earlier time in Mars’ history when the inclination of the planet’s spin axis allowed such deposits to form at lower latitudes than it does today. Just like on Earth, Mars’ tilt gives rises to seasons, but unlike Earth its tilt has changed dramatically over long periods of time.
“Understanding the history of water on Mars and if this once allowed life to flourish is at the heart of ESA’s ExoMars missions,” say mission scientists. “The spacecraft is not only returning spectacular images, but also providing the best ever inventory of the planet’s atmospheric gases with a particular emphasis on geologically and biologically important gases, and mapping the planet’s surface for water-rich locations.”
This topographical map of Mars from the Mars Global Surveyor laser altimeter instrument shows the various regions on Mars.Acidalia Planitia can be see at the top near the center. Credit: MGS/MOLA.
The ExoMars orbiter will also provide data relay services for the second ExoMars mission which has the Russian built Kazachok lander that will bring the Rosalind Franklin rover to the surface of Mars. That mission is scheduled to launch in September of 2022. When it arrives on Mars in 2023, the rover will explore another region of Mars – not yet disclosed — thought once to have hosted an ancient ocean, and will search underground for signs of life.
Is Mars home to an underwater lake? Different researchers are reaching different conclusions. Some say remote sensing from the Mars Express orbiter shows liquid water in an underground lake at Mars’ south polar region. Other researchers say clays or minerals explain the data better.
Who’s right? Maybe none of them.
A new study says that volcanic rock can explain the Mars Express data and that it’s a more plausible explanation.
The Martian lake hypothesis dates back to 2018 when a team of researchers published a paper presenting data from the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on the ESA’s Mars Express orbiter. The data showed a highly-reflective surface under the South Polar Layered Deposits (SPLD). In that paper, the researchers concluded that water was responsible for the signal and the Mars lake hypothesis gathered steam.
Then other researchers published other papers giving different explanations for the signal, showing how clays and minerals might be responsible. Then MARSIS data showed more reflective areas which scientists interpreted as more subsurface lakes. Recently the authors responsible for the 2018 paper that started it all published a research letter re-affirming their original interpretation of the data and refuting research that reached different conclusions.
Now a group of scientists published a paper saying the other researchers have it wrong. They conclude that volcanic rock is responsible for the MARSIS signal.
The title of their paper is “The Basal Detectability of an Ice-Covered Mars by MARSIS.” The journal Geophysical Research Letters published the paper, and the lead author is Cyril Grima, a planetary scientist at the University of Texas Institute for Geophysics (UTIG).
The hypothesis that there’s water under the SPLD relies on a couple of facts. The water must be briny to resist freezing, and the temperature can’t be too low. Obviously, there’s a lot more detail than that involved. But that’s the essence of it. The temperature is critical because different materials display different permittivity at different temperatures. And scientists don’t know exactly what the temperature is under the SPLD.
This is a map of the SPLD thickness, based on MARSIS measurements and MOLA surface topography. Image Credit: Plaut et al. 2007.
But this paper sets some of those concerns aside.
“For water to be sustained this close to the surface, you need both a very salty environment and a strong, locally generated heat source, but that doesn’t match what we know of this region,” lead author Cyril Grima said in a press release.
Rather than clays, minerals, or brines, this new research suggests that a type of volcanic rock that’s relatively common on Mars is responsible for the MARSIS data. If some of that volcanic rock were buried under the ice in the SPLD, then it would appear bright like water when MARSIS observed it.
In the study, Grima and his co-authors used computer models to add a global sheet of ice onto the Martian surface. This simulated one-mile-thick ice sheet allowed the researchers to compare features all across Mars’ surface with those under the real ice at the south pole. The SPLD is about 10% impure, and the team duplicated that in their simulated ice.
The result?
A radar map of Mars as seen through a mile of ice. UT Austin planetary scientist, Cyril Grima, built a computer model to cover the Red Planet in ice and observed how it changed the radar data. This caused volcanic plains (seen in red) to reflect radar in a manner that resembled liquid water. The finding challenges a 2018 study that appeared to find liquid water under Mars’ south polar cap. Credit: Cyril Grima
The team found bright reflections like those under the SPLD scattered across different latitudes. Many of them matched up with known locations of volcanic rock. Overall they found that between 0.3% and 2.0% of Mars’ surface could produce the same MARSIS signal detected under the SPLD. The bright terrains the team detected in their study are “… gathered within volcanic constructs of diverse geologic epoch,” the paper says.
Not all of Mars’ known volcanic terrains produce the same signal. But some pronounced volcanic features like shield volcanoes produced strong reflections. “A broad region of strong reflections is identified East of the Uranius Tholus interpreted as a shield volcano resulting from effusive eruptions of low viscosity lavas during the Hesperian-Amazonian transition,” the authors write.
The study showed a strong connection between known volcanic areas and reflectivity. This image shows the Uranius Tholus shield volcano in yellow. The team found strong reflections to the east of the volcano. Image Credit: Wikimedia
There’s a fascinating scientific debate playing out right now over the potential water under the SPLD. These results won’t end that debate, but they play a role. “It draws attention that the brightest terrains across the planet would produce basal echoes with a radiometric character in the range of the brightest ones observed at the SPLD by Orosei et al. (2018) and under similar assumptions for the composition of the overlying ice.” (Note: Orosei et al. 2018 is the original study presenting evidence for liquid water under the SPLD.)
“This radiometric similarity (or continuity) is indicative of the likelihood for a non-wet generic material currently available at Mars to be responsible for the bright basal SPLD reflection,” the paper’s conclusion says. The non-wet material is an iron-rich volcanic rock that’s common on Earth, too.
What do scientists on the other side of this issue think?
Dr. David Stillman is a geophysicist at the Southwest Research Institute (SwRI.) He’s a co-author of papers in support of the liquid water hypothesis.
He told Universe Today that Grima et al. is a robust study. “The Grima paper is very good,” Dr. Stillman said. But he identifies some potential discrepancies if we can call them that, and points them out.
“His paper makes the assumption that surface MARSIS amplitudes can be compared even though they were processed onboard Mars Express when Mars’ magnetosphere was varying. The reflectivity data used by the Italian group (Orosei et al. 2018) was not processed onboard so that amplitudes could be compared when Mars’ magnetosphere was varying (another issue with assumptions).” Dr. Stillman is referring to assumptions about Mars that all scientists have to make when studying the planet. In particular, scientists must work with assumptions about the subsurface temperature under the SPLD. The temperature affects the reflectivity of different compounds, altering the MARSIS signal.
Grima and his co-authors used a figure to present some of their findings in their paper. It highlights four areas on the surface of Mars that show high reflectivity under the simulated ice sheet and shows how volcanic rock can account for the signal.
This figure from the study shows the relative basal echo strength of Mars if the surface was entirely covered by a 1.4-km dirty ice sheet (10% volume impurity rate). Bottom inserts display only positive values for better identifications relative to the regional landforms. Image Credit: Grima et al. 2022.
According to Grima et al., the fact that these four regions are spread across longitudes is a significant strength in their results. “Four insets in Figure 3 highlight some of those regions where a positive Pss/Ps signature is consistent across longitudes instead of just being confined locally along an orbit (an indicator of possible data glitch),” the paper says.
But Dr. Stillman said there’s another possibility for those signals.
“Additionally, if you look at Fig 3 of Grima’s paper you will see very high surface reflection in the northern plains of Mars that likely does not have massive lava flows, but are due to artifacts due to the onboard processing,” he said.
“All those arrows point to high reflectivity that is likely just artifacts as the majority of these are in what we think are sediments and could not have high dielectric values or reflectivity,” Stillman pointed out. “Solis Planum also has pretty random high values, does this mean the whole thing has a high reflectivity or just like 10% of it?”
This won’t be the end of the debate, but it does reveal how intricate the problem is.
This issue is important to many in the planetary science community. If you scan the internet you can see it gets lots of attention and lots of commentary from other researchers even though Martian polar scientists form a fairly small, tightly-knitted community.
The coloured dots in this image represent sites where the ESA’s Mars Express Orbiter spotted bright radar reflections at Mars’ south polar cap. Some researchers interpret the reflections as subsurface liquid water, but other researchers have different explanations. Credits: ESA/NASA/JPL-Caltech
Isaac Smith is a Mars geophysicist at York University who’s not involved in any of these studies. In a press release, Smith explained that the highly reflective signal could be explained by a type of clay dissolved in water. This phenomenon is present on Earth and could be on Mars, too.
Smith also points out that if Grima is right about the reflective signal, it’s not all bad when it comes to the larger issue of Martian water.
“I think the beauty of Grima’s finding is that while it knocks down the idea there might be liquid water under the planet’s south pole today, it also gives us really precise places to go look for evidence of ancient lakes and riverbeds and test hypotheses about the wider drying out of Mars’ climate over billions of years,” Smith said.
We’re in a position between competing hypotheses. But we’re not stuck. This is how science works.
“Science isn’t foolproof on the first try,” said Smith. “That’s especially true in planetary science where we’re looking at places no one’s ever visited and relying on instruments that sense everything remotely.”
Dr. Stillman seems to agree and points out that everyone is forced to make some assumptions when it comes to Mars.
“Honestly, I do not know which assumptions are correct because we are studying a planet so far away with very limited data,” he told Universe Today.
None of the papers published so far proves there’s water, and none prove there isn’t. Instead, we’re inching our way toward knowing for sure.
We need better data, which means we need another mission to Mars.
