An artist's conception of a violent flare erupting from the red dwarf star Proxima Centauri. Such flares can obliterate atmospheres of nearby planets. Credit: NRAO/S. Dagnello.
Proxima b, the closest exoplanet to our Solar System, has been a focal point of scientific study since it was first confirmed (in 2016). This terrestrial planet (aka. rocky) orbits Proxima Centauri, an M-type (red dwarf) star located 4.2 light-years beyond our Solar System – and is a part of the Alpha Centauri system. In addition to its proximity and rocky composition, it is also located within its parent star’s habitable zone (HZ).
Until a mission can be sent to this planet (such as Breakthrough Starshot), astrobiologists are forced to postulate about the possibility that life could exist there. Unfortunately, an international campaign that monitored Proxima Centauri for months using nine space- and ground-based telescopes recently spotted an extreme flare coming from the star, one which would have rendered Proxima b uninhabitable.
Sometimes the sun spits out high-energy particles which slam into the Earth, potentially disrupting our sensitive electronics. New research has found that these particles originate in the plasma of the sun itself, and are trapped there by strong magnetic fields. When those fields weaken, the particles blast out.
Flares from the sun are some of the nastiest things in the solar system. When the sun flares, it belches out intense X-ray radiation (and sometimes even worse). Predicting solar flares is a tricky job, and a new research paper sheds light on a possible new technique: looking for telltale ripples in the surface of the sun minutes before the blast comes.
X9.3 Flare blasts off the Sun. Image credit: NASA/GSFC/SDO
Since it launched in 2010, the Solar Dynamics Observatory has helped scientists understand how the Sun’s magnetic field is generated and structured, and what causes solar flares. One of the main goals of the mission was to be able to create forecasts for predicting activity on the Sun.
Using mission data from the past 10 years, SDO scientists have now developed a new model that successfully predicted seven of the Sun’s biggest flares from the last solar cycle, out of a set of nine.
GOES-17 Solar Ultraviolet Imager captures the Sun at different wavelengths. Credit: NOAA
Our Sun is the source of life on Earth. Its calm glow across billions of years has allowed life to evolve and flourish on our world. This does not mean our Sun doesn’t have an active side. We have observed massive solar flares, such as the 1859 Carrington event, which produced northern lights as far south as the Caribbean, and drove electrical currents in telegraph lines. If such a flare occurred in Earth’s direction today, it would devastate our electrical infrastructure. But fortunately for us, the Sun is mostly calm. Unusually calm when compared to other stars.
An artist's conception of a superflare event, on a dwarf star. Image credit: Mark Garlick/University of Warwick
Earthlings are fortunate. Our planet has a robust magnetic shield. Without out magnetosphere, the Sun’s radiation would’ve probably ended life on Earth before it even got going. And our Sun is rather tame, in stellar terms.
What’s it like for exoplanets orbiting more active stars?
An illustration of the powerful CME detected coming from OU Andromedae. Image Credit: NASA/CXC/INAF/Argiroffi, C. et al.
Illustration: NASA/GSFC/S. Wiessinger
For the first time ever, astronomers have witnessed a coronal mass ejection (CME) on a star other than our very own Sun. The star, named HR 9024 (and also known as OU Andromeda,) is about 455 light years away, in the constellation Andromeda. It’s an active, variable star with a strong magnetic field, which astronomers say may cause CMEs.
“This result, never achieved before, confirms that our understanding of the main phenomena that occur in flares is solid.”
Costanza Argiroffi, Lead Author, University of Palermo, and Associate Researcher at the National Institute for Astrophysics in Italy.
Artist's impression of a flaring red dwarf star, orbited by an exoplanet. Credit: NASA, ESA, and G. Bacon (STScI)
Since its discovery was announced in August of 2016, Proxima b has been an endless source of wonder and the target of many scientific studies. In addition to being the closest extra-solar planet to our Solar System, this terrestrial planet also orbits within Proxima Centauri’s circumstellar habitable zone (aka. “Goldilocks Zone”). As a result, scientists have naturally sought to determine if this planet could actually be home to extra-terrestial life.
Many of these studies have been focused on whether or not Proxima b could retain an atmosphere and liquid water on its surface in light of the fact that it orbits an M-type (red dwarf) star. Unfortunately, many of these studies have revealed that this is not likely due to flare activity. According to a new study by an international team of scientists, Proxima Centauri released a superflare that was so powerful, it would have been lethal to any life as we know it.
The study, titled “The First Naked-Eye Superflare Detected from Proxima Centauri“, recently appeared online. The team was led by Howard Ward, a PhD candidate in physics and astronomy at the UNC Chapel Hill, with additional members from the NASA Goddard Space Flight Center, the University of Washington, the University of Colorado, the University of Barcelona and the School of Earth and Space Exploration at Arizona State University.
Artist impression of a red dwarf star like Proxima Centauri, the nearest star to our sun. New analysis of ALMA observations reveal that Proxima Centauri emitted a powerful flare that would have created inhospitable conditions for planets in that system. Credit: NRAO/AUI/NSF; D. Berry
As they indicate in their study, solar flare activity would be one of the greatest potential threats to planetary habitability in a system like Proxima Centauri. As they explain:
“[W]hile ozone in an Earth-like planet’s atmosphere can shield the planet from the intense UV flux associated with a single superflare, the atmospheric ozone recovery time after a superflare is on the order of years. A sufficiently high flare rate can therefore permanently prevent the formation of a protective ozone layer, leading to UV radiation levels on the surface which are beyond what some of the hardiest-known organisms can survive.”
In addition stellar flares, quiescent X-ray emissions and UV flux from a red dwarf star can would be capable of stripping planetary atmospheres over the course of several billion years. And while multiple studies have been conducted that have explored low- and moderate-energy flare events on Proxima, only one high-energy event has even been observed.
Artist’s impression of Proxima b, which was discovered using the Radial Velocity method. Credit: ESO/M. Kornmesser
As the team indicates in their study, the March 2016 superflare was the first to be observered from Proxima Centauri, and was rather powerful:
“In March 2016 the Evryscope detected the first-known Proxima superflare. The superflare had a bolometric energy of 10^33.5 erg, ~10× larger than any previously-detected flare from Proxima, and 30×larger than any optically measured Proxima flare. The event briefly increased Proxima’s visible-light emission by a factor of 38× averaged over the Evryscope’s 2-minute cadence, or ~68× at the cadence of the human eye. Although no M-dwarfs are usually visible to the naked-eye, Proxima briefly became a magnitude-6.8 star during this superflare, visible to dark-site naked-eye observers.”
The superflare coincided with the three-month Pale Red Dot campaign, which was responsible for first revealing the existence of Proxima b. While monitoring the star with the HARPS spectrograph – which is part of the 3.6 m telescope at the ESO’s La Silla Observatory in Chile – the campaign team also obtaining spectra on March 18th, 08:59 UT (just 27 minutes after the flare peaked at 08:32 UT).
The team also noted that over the last two years, the Evryscope has recorded 23 other large Proxima flares, ranging in energy from 10^30.6 erg to 10^32.4 erg. Coupled with rates of a single superflare detection, they predict that at least five superflares occur each year. They then combined this data with the high-resolution HARPS spectroscopy to constrain the superflare’s UV spectrum and any associated coronal mass ejections.
The Red Dots project is successor to the Pale Red Dot project, which discovered Proxima b last summer. Credit: ESO
The team then used the HARPS spectra and the Evryscope flare rates to create a model to determine what effects this star would have on a nitrogen-oxygen atmosphere. This included how long the planet’s protective ozone layer would be able to withstand the blasts, and what effect regular exposure to radiation would have on terrestrial organisms.
“[T]he repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years. We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100× the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares.”
Essentially, this and other studies have concluded that any planets orbiting Proxima Centauri would not be habitable for very long, and likely became lifeless balls of rock a long time ago. But beyond our closest neighboring star system, this study also has implications for other M-type star systems. As they explain, red dwarf stars are the most common in our galaxy – roughly 75% of the population – and two-thirds of these stars experience active flare activity.
As such, measuring the impact that superflares have on these worlds will be a necessary component to determining whether or not exoplanets found by future missions are habitable. Looking ahead, the team hopes to use the Evryscope to examine other star systems, particularly those that are targets for the upcoming Transiting Exoplanet Survey Satellite (TESS) mission.
Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO
“Beyond Proxima, Evryscope has already performed similar long-term high-cadence monitoring of every other Southern TESS planet-search target, and will therefore be able to measure the habitability impact of stellar activity for all Southern planetsearch-target M-dwarfs,” they write. “In conjunction with coronal-mass-ejection searches from long- wavelength radio arrays like the [Long Wavelength Array], the Evryscope will constrain the long-term atmospheric effects of this extreme stellar activity.”
For those who hoped that humanity might find evidence of extra-terrestrial life in their lifetimes, this latest study is certainly a letdown. It’s also disappointing considering that in addition to being the most common type of star in the Universe, some research indicates that red dwarf stars may be the most likely place to find terrestrial planets. However, even if two-thirds of these stars are active, that still leaves us with billions of possibilities.
It is also important to note that these studies help ensure that we can determine which exoplanets are potentially habitable with greater accuracy. In the end, that will be the most important factor when it comes time to decide which of these systems we might try to explore directly. And if this news has got you down, just remember the worlds of the immortal Carl Sagan:
“The universe is a pretty big place. If it’s just us, seems like an awful waste of space.”
The darker area on this image of the Sun's surface is the southern extension of the northern hemisphere polar corona. The coronal hole is a source of fast-moving streams of particles from the Sun, which can cause auroras here on Earth. Image: NASA/SDO
To the naked eye, the Sun puts out energy in a continual, steady state, unchanged through human history. (Don’t look at the sun with your naked eye!) But telescopes tuned to different parts of the electromagnetic spectrum reveal the Sun’s true nature: A shifting, dynamic ball of plasma with a turbulent life. And that dynamic, magnetic turbulence creates space weather.
Space weather is mostly invisible to us, but the part we can see is one of nature’s most stunning displays, the auroras. The aurora’s are triggered when energetic material from the Sun slams into the Earth’s magnetic field. The result is the shimmering, shifting bands of color seen at northern and southern latitudes, also known as the northern and southern lights.
This image of the northern lights over Canada was taken by a crew member on board the ISS in Sept. 2017. Image: NASA
There are two things that can cause auroras, but both start with the Sun. The first involves solar flares. Highly-active regions on the Sun’s surface produce more solar flares, which are sudden, localized increase in the Sun’s brightness. Often, but not always, a solar flare is coupled with a coronal mass ejection (CME).
A coronal mass ejection is a discharge of matter and electromagnetic radiation into space. This magnetized plasma is mostly protons and electrons. The CME ejection often just disperses into space, but not always. If it’s aimed in the direction of the Earth, chances are we get increased auroral activity.
The second cause of auroras are coronal holes on the Sun’s surface. A coronal hole is a region on the surface of the Sun that is cooler and less dense than surrounding areas. Coronal holes are the source of fast-moving streams of material from the Sun.
Whether it’s from an active region on the Sun full of solar flares, or whether it’s from a coronal hole, the result is the same. When the discharge from the Sun strikes the charged particles in our own magnetosphere with enough force, both can be forced into our upper atmosphere. As they reach the atmosphere, they give up their energy. This causes constituents in our atmosphere to emit light. Anyone who has witnessed an aurora knows just how striking that light can be. The shifting and shimmering patterns of light are mesmerizing.
The auroras occur in a region called the auroral oval, which is biased towards the night side of the Earth. This oval is expanded by stronger solar emissions. So when we watch the surface of the Sun for increased activity, we can often predict brighter auroras which will be more visible in southern latitudes, due to the expansion of the auroral oval.
This photo is of the aurora australis over New Zealand. Image: Paul Stewart, Public Domain, CC 1.0 Universal.
Something happening on the surface of the Sun in the last couple days could signal increased auroras on Earth, tonight and tomorrow (March 28th, 29th). A feature called a trans-equatorial coronal hole is facing Earth, which could mean that a strong solar wind is about to hit us. If it does, look north or south at night, depending on where your live, to see the auroras.
Of course, auroras are only one aspect of space weather. They’re like rainbows, because they’re very pretty, and they’re harmless. But space weather can be much more powerful, and can produce much greater effects than mere auroras. That’s why there’s a growing effort to be able to predict space weather by watching the Sun.
A powerful enough solar storm can produce a CME strong enough to damage things like power systems, navigation systems, communications systems, and satellites. The Carrington Event in 1859 was one such event. It produced one of the largest solar storms on record.
That storm occurred on September 1st and 2nd, 1859. It was preceded by an increase in sun spots, and the flare that accompanied the CME was observed by astronomers. The auroras caused by this storm were seen as far south as the Caribbean.
Sunspots are dark areas on the surface of the Sun that are cooler than the surrounding areas. They form where magnetic fields are particularly strong. The highly active magnetic fields near sunspots often cause solar flares. Image: NASA/SDO/AIA/HMI/Goddard Space Flight Center
The same storm today, in our modern technological world, would wreak havoc. In 2012, we almost found out exactly how damaging a storm of that magnitude could be. A pair of CMEs as powerful as the Carrington Event came barreling towards Earth, but narrowly missed us.
We’ve learned a lot about the Sun and solar storms since 1859. We now know that the Sun’s activity is cyclical. Every 11 years, the Sun goes through its cycle, from solar maximum to solar minimum. The maximum and minimum correspond to periods of maximum sunspot activity and minimum sunspot activity. The 11 year cycle goes from minimum to minimum. When the Sun’s activity is at its minimum in the cycle, most CMEs come from coronal holes.
NASA’s Solar Dynamics Observatory (SDO), and the combined ESA/NASA Solar and Heliospheric Observatory (SOHO) are space observatories tasked with studying the Sun. The SDO focuses on the Sun and its magnetic field, and how changes influence life on Earth and our technological systems. SOHO studies the structure and behavior of the solar interior, and also how the solar wind is produced.
Several different websites allow anyone to check in on the behavior of the Sun, and to see what space weather might be coming our way. The NOAA’s Space Weather Prediction Center has an array of data and visualizations to help understand what’s going on with the Sun. Scroll down to the Aurora forecast to watch a visualization of expected auroral activity.
NASA’s Space Weather site contains all kinds of news about NASA missions and discoveries around space weather. SpaceWeatherLive.com is a volunteer run site that provides real-time info on space weather. You can even sign up to receive alerts for upcoming auroras and other solar activity.
A massive prominence erupts from the surface of the sun. Credit: NASA Goddard Space Flight Center
In today’s modern, fast-paced world, human activity is very much reliant on electrical infrastructure. If the power grids go down, our climate control systems will shut off, our computers will die, and all electronic forms of commerce and communication will cease. But in addition to that, human activity in the 21st century is also becoming increasingly dependent upon the infrastructure located in Low Earth Orbit (LEO).
Aside from the many telecommunications satellites that are currently in space, there’s also the International Space Station and a fleet of GPS satellites. It is for this reason that solar flare activity is considered a serious hazard, and mitigation of it a priority. Looking to address that, a team of scientists from Harvard University recently released a study that proposes a bold solution – placing a giant magnetic shield in orbit.
The study – which was the work of Doctor Manasavi Lingam and Professor Abraham Loeb from the Harvard Smithsonian Center for Astrophysicist (CfA) – recently appeared online under the title “Impact and Mitigation Strategy for Future Solar Flares“. As they explain, solar flares pose a particularly grave risk in today’s world, and will become an even greater threat due to humanity’s growing presence in LEO.
Solar flares have been a going concern for over 150 years, ever since the famous Carrington Event of 1859. Since that time, a great deal of effort has been dedicated to the study of solar flares from both a theoretical and observational standpoint. And thanks to the advances that have been made in the past 200 years in terms of astronomy and space exploration, much has been learned about the phenomena known as “space weather”.
At the same time, humanity’s increased reliance on electricity and space-based infrastructure have also made us more vulnerable to extreme space weather events. In fact, if the Carrington event were to take place today, it is estimated that it would cause global damage to electric power grids, satellites communications, and global supply chains.
The cumulative worldwide economic losses, according to a 2009 report by the Space Studies Board (“Severe Space Weather Events–Understanding Societal and Economic Impacts”), would be $10 trillion, and recovery would take several years. And yet, as Professor Loeb explained to Universe Today via email, this threat from space has received far less attention than other possible threats.
“In terms of risk from the sky, most of the attention in the past was dedicated to asteroids,” said Loeb. “They killed the dinosaurs and their physical impact in the past was the same as it will be in the future, unless their orbits are deflected. However, solar flares have little biological impact and their main impact is on technology. But a century ago, there was not much technological infrastructure around, and technology is growing exponentially. Therefore, the damage is highly asymmetric between the past and future.”
Artist’s concept of a large asteroid passing by the Earth-Moon system. Credit: A combination of ESO/NASA images courtesy of Jason Major/Lights in the Dark.
To address this, Lingham and Loeb developed a simple mathematical model to assess the economic losses caused by solar flare activity over time. This model considered the increasing risk of damage to technological infrastructure based on two factors. For one, they considered the fact that the energy of a solar flares increases with time, then coupled this with the exponential growth of technology and GDP.
What they determined was that on longer time scales, the rare types of solar flares that are very powerful become much more likely. Coupled with humanity’s growing presence and dependence on spacecraft and satellites in LEO, this will add up to a dangerous conjunction somewhere down the road. Or as Loeb explained:
“We predict that within ~150 years, there will be an event that causes damage comparable to the current US GDP of ~20 trillion dollars, and the damage will increase exponentially at later times until technological development will saturate. Such a forecast was never attempted before. We also suggest a novel idea for how to reduce the damage from energetic particles by a magnetic shield. This was my idea and was not proposed before.”
To address this growing risk, Lingham and Loeb also considered the possibility of placing a magnetic shield between Earth and the Sun. This shield would be placed at the Earth-Sun Lagrange Point 1, where it would be able to deflect charged particles and create an artificial bowshock around Earth. In this sense, this shield would protect Earth’s in a way that is similar to what its magnetic field already does, but to greater effect.
Illustration of the proposed magnetic deflector placed at the Earth-Sun L1 Lagrange Point. Credit: Lingam and Loeb, 2017
Based on their assessment, Lingham and Loeb indicate that such a shield is technically feasible in terms of its basic physical parameters. They were also able to provide a rudimentary timeline for the construction of this shield, not to mention some rough cost assessments. As Loeb indicated, such a shield could be built before this century is over, and at a fraction of the cost of what would be incurred from solar flare damage.
“The engineering project associated with the magnetic shield that we propose could take a few decades to construct in space,” he said. “The cost for lifting the needed infrastructure to space (weighting 100,000 tons) will likely be of order 100 billions of dollars, much less than the expected damage over a century.”
Interestingly enough, the idea of using a magnetic shield to protect planets has been proposed before. For example, this type of shield was also the subject of a presentation at this year’s “Planetary Science Vision 2050 Workshop“, which was hosted by NASA’s Planetary Science Division (PSD). This shield was recommended as a means of enhancing Mars’ atmosphere and facilitating crewed mission to its surface in the future.
During the course of the presentation, titled “A Future Mars Environment for Science and Exploration“, NASA Director Jim Green discussed how a magnetic shield could protect Mars’ tenuous atmosphere from solar wind. This would allow it to replenish over time, which would have the added benefit of warming Mars up and allowing liquid water to again flow on its surface. If this sounds similar to proposals for terraforming Mars, that’s because it is!
Artist’s impression of a flaring red dwarf star, orbited by an exoplanet. Credit: NASA, ESA, and G. Bacon (STScI)
Beyond Earth and the Solar System, the implications for this study are quite overwhelming. In recent years, many terrestrial planets have been found orbiting within nearby M-type (aka. red dwarf) star systems. Because of the way these planets orbit closely to their respective suns, and the variable and unstable nature of M-type stars, scientists have expressed doubts about whether or not these planets could actually be habitable.
In short, scientists have ventured that over the course of billions of years, rocky planets that orbit close to their suns, are tidally-locked with them, and are subject to regular solar flares would lose their atmospheres. In this respect, magnetic shields could be a possible solution to creating extra-solar colonies. Place a large shield in orbit at the L1 Lagrange point, and you never have to worry again about powerful magnetic storms ravaging the planet!
On top of that, this study offers a possible resolution to the Fermi Paradox. When looking for sign of Extra-Terrestrial Intelligence (ETI), it might make sense to monitor distant stars for signs of an orbiting magnetic shield. As Prof. Leob explained, such structures may have already been detected around distant stars, and could explain some of the unusual observations astronomers have made:
“The imprint of a shield built by another civilization could involve the changes it induces in the brightness of the host star due to occultation (similar behavior to Tabby’s star) if the structure is big enough. The situation could be similar to Dyson’s spheres, but instead of harvesting the energy of the star the purpose of the infrastructure is to protect a technological civilization on a planet from the flares of its host star.”
It is a foregone conclusion that as time and technology progress, humanity’s presence in (and reliance on) space will increase. As such, preparing for the most drastic space weather events the Solar System can throw at us just makes sense. And when it comes to the big questions like “are we alone in the Universe?”, it also makes sense to take our boldest concepts and proposals and consider how they might point the way towards extra-terrestrial intelligence.
