Voyager 2 Has Left the (Interplanetary) Building

The NASA probe was launched in 1977 and has now joined its twin, Voyager 1, to begin a new chapter of interstellar discovery

Both Voyager 1 and 2 are sampling particles from the interstellar medium, becoming humanity’s furthest-flung missions into deep space [NASA/JPL-Caltech]

Carolyn Porco, planetary scientist and lead of the NASA Cassini mission imaging team, probably said it best:

Voyager 1 made us an interstellar species; 6 yrs later, Voyager 2 makes it look easy. While these are historic, soul-stirring achievements, I am most happy right now that Ed Stone, the best Project Scientist who ever lived, lived to see this moment. 

via Twitter

It can be easy to lump today’s announcement about Voyager 2 entering interstellar space as “simply” another magnificent science achievement for NASA — but that would be too narrow; the Voyager spacecraft have become so much more. They represent humanity at our best; our will to explore, our need to push boundaries, our excitement for expanding the human experience far beyond terrestrial shores. They also act as a means to understand the sheer scale of our solar system. And what better way to measure that scale than with a human life. 

Ed Stone started working on the Voyager Program in 1972 as a project scientist. Now, at 82 years old, he’s still working on the Voyagers nearly half a century later as they continue to send back data from the frontier beyond our solar system. When we start measuring space missions in half-centuries, or missions that have lasted entire careers, it becomes clear how far we’ve come. Not only does NASA build really tough space robots that surpass expectations routinely, returning new discoveries and revelations about the universe that surrounds us, the Voyagers have become a monument to the essence of being human, something with which Stone would probably agree.

Although most of the instruments aboard the Voyagers are no longer functional, both missions are still returning data from the shores of the interstellar ocean and, on Nov. 5, mission controllers noticed that one of Voyager 2’s instruments, the Plasma Science Experiment (PSE), had detected a rapid change in its surrounding environment. Used to being immersed the comparatively warm and tenuous solar wind flowing past it, its plasma measurements detected a change. The spacecraft had passed into a region of space where the plasma was now denser and cooler. Three other particle experiments also detected a dramatic change; solar wind particle counts were down, but cosmic ray counts precipitously increased. Voyager 1’s PSE failed in 1980, so couldn’t measure this boundary when it entered interstellar space in 2012, so Voyager 2 is adding more detail about what we can expect happens when a spacecraft travels from the heliosphere, through the heliopause and into interstellar space. 

[NASA/JPL-Caltech]

“There is still a lot to learn about the region of interstellar space immediately beyond the heliopause,” said Stone in a NASA statement.

The heliosphere can be imagined as a vast magnetized bubble that is generated by the Sun. This bubble is inflated by the solar wind, a persistent stream of solar particles that ebb and flow with the Sun’s 11-year cycle. When the Sun is at its most active, the bubble expands; at its least active, it contracts. This dynamic solar sphere of influence affects the flux of high-energy cosmic rays entering the inner solar system, but the physics at this enigmatic boundary is poorly understood. With the help of the Voyagers, however, we’re getting an in-situ feel for the plasma environment at the boundary of where the Sun’s magnetism hits the interstellar medium.

To achieve this, however, we had to rely on two spacecraft that were launched before I was born, in 1977. Voyager 2 is now 11 billion miles away (Voyager 1 is further away, at nearly 14 billion miles) and it took the probe 41 years just to reach our interstellar doorstep. Neither Voyagers have “left” the solar system, not by a long shot. The gravitational boundary of the solar system is thought to lie some 100,000 AU (astronomical units, where one AU is the average distance from the Earth to the Sun), the outermost limit to the Oort Cloud — a region surrounding the solar system that contains countless billions of icy objects, some of which become the long-period comets that intermittently careen through the inner solar system. Voyager 2 is barely 120 AU from Earth, so as you can see, it has a long way to go (probably another 30,000 years) before it really leaves the solar system — despite what the BBC tells us.

So, tonight, as we ponder our existence on this tiny pale blue dot, look up and think of the two space robot pioneers that are still returning valuable data despite being in deep space for over four decades. I hope their legacy lives on well beyond the life of their radioactive generators, and that the next interstellar spacecraft (no pressure, New Horizons) lives as long, if not longer, than the Voyagers.

Read more about today’s news in my article for HowStuffWorks.com.

  

Did a Solar Storm Detonate Dozens of Vietnam War Mines?

Some 25 underwater mines mysteriously exploded in the summer of 1972. A newly declassified report points its finger at a surprising culprit: the sun.

[NASA/SDO]

Something very strange happened on Aug. 4, 1972 in the waters near Vietnam. Dozens of undersea mines detonated for seemingly no reason. The matter was classified, as was a report trying to get to the bottom of what happened. Initial hypotheses focused on a malfunctioning self-destruct feature meant to prevent lost mines from posing an underwater hazard for decades after hostilities were over, but there was no corroborating evidence. Soviet subs might have accounted for one or two, but not systematic detonations across the whole minefield, not to mention their defensive countermeasures.

But one of the suggestions seemed to very neatly explain the observed phenomenon. The mines were magnetic, meaning that they reacted to the natural magnetism of metals in ships’ hulls and the changes in the strengths of their magnetic fields as those ships approached. It was an old, reliable technology and it would’ve taken a massive magnetic event to have set them off. And wouldn’t you know it, some of the most intense solar activity on record happened in that exact time frame, causing numerous power surges and telegraph outages across North America.

On the day Navy aircraft saw the mines go off, the sun erupted in what’s known as an X-class flare, a burst of energy more than 10,000 times more powerful than the high end of typical solar emissions. With the path to Earth cleared by supercharged solar winds, the resulting coronal mass ejection hit Earth in just 14.6 hours instead of the typical three days and caused massive magnetic and electrical disruptions in the atmosphere, quite possibly powerful enough to set off detectors on the underwater mines off the coast of Hon La Port as the plasma slammed into our planet.

So, case closed? Not exactly. We measure the intensity of the disruption in the Earth’s magnetic field caused by solar storms in negative nTs, or nano-Teslas. By itself, a nano-Tesla isn’t much. Your run of the mill fridge magnet is a million times stronger, although it’s only spread over tens of square centimeters, instead of millions of square kilometers like the fraction of a coronal mass ejection that hits Earth and lingers in the upper layers of the atmosphere. In 2003, a massive flare hit us with a magnetic disruption measuring almost -400 nT without melting anything down, although it did cause problems with air traffic.

By comparison, the ejection in 1972 measured a third of that at just -125 nT. Was it really strong enough to set off underwater mines? We’ll probably never know for sure, but it’s still entirely possible. Over the decades, we’ve learned much more about solar storms and what they can do, developed better shielding and early warning systems, more sophisticated equipment, and unwittingly created a shield of radio emissions to reroute charged particles from Earth. It’s quite plausible that older, less insulated technology was more sensitive to major solar storms and the trigger mechanisms for those mines were just one example.

[This article originally appeared on World of Weird Things]

Proxima Centauri Unleashes ‘Doomsday’ Flare

Proxima b just got roasted.

flarestar
Proxima b weather report: Sunny with the chance of a flare of doom (NASA)

Having a bad day? Well, spare a thought for any hypothetical aliens living on Proxima b.

Proxima Centauri is a small, dim M dwarf—commonly known as a red dwarf—located approximately 4.2 light-years away. Over the last couple of years, this diminutive star has spent a lot of time in the headlines after the discovery of a small rocky world, called Proxima b, inside the star’s habitable zone.

With the knowledge that there’s a potentially temperate world on our cosmic doorstep, speculation started to fly that this exoplanet could become a future interstellar destination for humanity or that it’s not just a “habitable” world, perhaps it’s inhabited, too.

Putting aside the fact that we have no idea whether this interesting exoplanet possesses water of any kind, let alone if it even has an atmosphere (two pretty important ingredients for life as we know it), it is certainly an incredible find. But there are some caveats to Proxima b’s habitability and the main one is the unpredictability of its star.

The problem with red dwarfs is that they are angry little stars. In fact, they have long been known as “flare stars” as, well, they produce flares. What they lack in energy output they certainly make up for in explosions. Really, really big explosions.

Last March, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile detected a cataclysmic stellar flare erupting from Proxima Centauri, and this thing put anything our Sun can produce to shame.

“March 24, 2017, was no ordinary day for Proxima Cen,” said astronomer Meredith MacGregor, of the Carnegie Institution for Science in Washington D.C., in a statement.

Over just ten seconds on that special day, a powerful flare boosted Proxima Centauri’s brightness by over 1,000 times greater than normal. This mega-flare event was preceded by a smaller flare event and both flares occurred over a two minute period.

nrao18cb03b
The brightness of Proxima Centauri as observed by ALMA over the two minutes of the event on March 24, 2017 (Meredith MacGregor, Carnegie)

Although astronomers have little idea where Proxima b was in relation to the flaring site, it would have undoubtedly received one hell of a radiation dose from the eruption.

“It’s likely that Proxima b was blasted by high energy radiation during this flare,” said MacGregor. “Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilized the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water.”

The habitable zone around any star is the distance at which a world must orbit to receive just the right amount of energy to maintain water in a liquid state. Liquid water, as we all know, is necessary for life (as we know it) to evolve. Whereas the Earth orbits the Sun at an average distance of nearly 100 million miles (a distance that unsurprisingly puts us inside our star’s habitable zone), for a star as cool as Proxima Centauri, its habitable zone is closer. Much, much closer. This means Proxima b, with an orbital distance of approximately 4.6 million miles, is nearly 22 times closer to its star than the Earth is to the Sun. Orbiting so close to a star pumping out a flare ten times more powerful than the largest flare our Sun can generate is the space weather equivalent of sitting inside the blast zone of a nuclear weapon.

As MacGregor argues, Proxima Centauri is known to generate these kinds of flares, and Proxima b has been bathed in its radiation for eons. It doesn’t seem likely that the exoplanet would be able to form an atmosphere, let alone hold onto one.

So, what of Proxima b’s hypothetical aliens? Well, unless they’ve found a niche deep under layers of ice and/or rock, it seems that this “habitable” world is anything but.

For more on why Proxima b would be a bad place to take your honeymoon, read
Sorry, Proxima Centauri Is Probably a Hellhole, Too.

Sun Erupts With a Monster X9-Class Solar Flare — Earth Feels Its Punch

Sept_6_X9_Blend_131-171_print
Credit: NASA/SDO

This morning, the sun erupted with the most powerful solar flare in a decade, blasting the Earth’s upper atmosphere with energetic X-ray and extreme ultraviolet (EUV) radiation.

The flare was triggered by intense magnetic activity over an active region called AR2673 that has been roiling with sunspot activity for days, threatening an uptick in space weather activity. As promised, that space weather brought an explosive event at 1202 UTC (8:02 a.m. PT) that ionized the Earth’s upper atmosphere and causing a shortwave radio blackout over Europe, Africa and the Atlantic Ocean, reports Spaceweather.com.

blackoutmap
Radio blackout map: When the Earth’s ionosphere is energized by X-ray and EUV radiation from solar flares, certain radio frequencies are absorbed by increased ionization of certain layers of the atmosphere, posing issues for global radio communications (NOAA)

The powerful X9.3-class flare came after an earlier X2.2 blast from the same active region, a significant flare in itself. X-class flares are the most powerful type of solar flares.

The electromagnetic radiation emitted by flaring events affect the Earth’s ionosphere immediately, but now space weather forecasters are on the lookout for a more delayed impact of this eruption.

x-class-solar-flare
The powerful X9-class solar flare erupted from the active region (AR) 2673, a large cluster of sunspots — seen here by NASA’s Solar Dynamics Observatory (NASA/SDO)

Solar flares can create magnetic instabilities that may launch coronal mass ejections (CMEs) — basically vast magnetized bubbles of energetic solar plasma — into interplanetary space. Depending on the conditions, these CMEs may take hours or days to reach Earth (if they are Earth-directed) and can generate geomagnetic storms should they collide and interact with our planet’s global magnetic field.

Update: According to observations gathered by NASA’s STEREO-A spacecraft, the flare did produce a CME and space weather forecasters are determining its trajectory to see whether it is Earth-directed. Also, NASA has produced a series of beautiful images from the SDO, showing the flare over a range of frequencies.

The Sun Just Unleashed a Massive Explosion — at Mars

cme_c3_anim
NASA/ESA/SOHO

The Earth and Mars are currently on exact opposite sides of the sun — a celestial situation known as “Mars solar conjunction” — a time when we have no way of directly communicating with satellites and rovers at the Red Planet. So, when the Solar and Heliospheric Observatory (SoHO) spotted a huge (and I mean HUGE) bubble of superheated plasma expand from the solar disk earlier today (July 23), it either meant our nearest star had launched a vast coronal mass ejection directly at Earth or it had sent a CME in the exact opposite direction.

As another solar observatory — the STEREO-A spacecraft — currently has a partial view of the other side of the sun (it orbits ahead of Earth’s orbit, so it can see regions of the sun that are out of view from our perspective), we know that this CME didn’t emanate from the sun’s near side, it was actually launched away from us and Mars will be in for some choppy space weather very soon.

It appears the CME emanated from active region (AR) 2665, a region of intense magnetic activity exhibiting a large sunspot.

“If this explosion had occurred 2 weeks ago when the huge sunspot was facing Earth, we would be predicting strong geomagnetic storms in the days ahead,” writes Tony Phillips of Spaceweather.com.

CMEs are magnetic bubbles of solar plasma that are ejected at high speed into interplanetary space following a magnetic eruption in the lower corona (the sun’s lower atmosphere). From STEREO-A’s unique vantage point, it appears the CME detected by SoHO was triggered by a powerful solar flare that generated a flash of extreme-ultraviolet radiation (possibly even generating X-rays):

stereoa
Observation by STEREO-A of the flaring event that likely triggered today’s CME (NASA/STEREO)

When CMEs encounter Earth’s global magnetic field, the radiation environment surrounding our planet increases, posing a hazard for satellites and unprotected astronauts. In addition, if the conditions are right, geomagnetic storms may commence, creating bright aurorae at high latitudes. These storms can overload power grids on the ground, triggering mass blackouts. Predicting when these storms will occur is of paramount importance, so spacecraft such as SoHO, STEREO and others are constantly monitoring our star’s magnetic activity deep inside the corona and throughout the heliosphere.

Mars, however, is a very different beast to Earth in that it doesn’t have a strong global magnetosphere to shield against incoming energetic particles from the sun, which the incoming CME will be delivering very soon. As it lacks a magnetic field, this CME will continue to erode the planet’s thin atmosphere, stripping some of the gases into space. Eons of space weather erosion has removed most of the Martian atmosphere, whereas Earth’s magnetism keeps our atmospheric gases nicely contained.

When NASA and other space agencies check in with their Mars robots after Mars solar conjunction, it will be interesting to see if any recorded the space weather impacts of this particular CME.

h/t Spaceweather.com

TRAPPIST-1: The ‘Habitable’ Star System That’s Probably a Hellhole

trappist-1-star
Red dwarfs can be angry little stars (NASA/GSFC/S. Wiessinger)

There are few places that elicit such vivid thoughts of exotic habitable exoplanets than TRAPPIST-1 — a star system located less than 40 light-years from Earth. Alas, according to two recent studies, the planetary system surrounding the tiny red dwarf star may actually be horrible.

For anyone who knows a thing or two about red dwarfs, this may not come as a surprise. Although they are much smaller than our sun, red dwarfs can pack a powerful space weather punch for any world that orbits too close. And, by their nature, any habitable zone surrounding a red dwarf would have to be really compact, a small detail that would bury any “habitable” exoplanet in a terrible onslaught of ultraviolet radiation and a blowtorch of stellar winds. These factors would make the space weather environment around TRAPPIST-1 extreme to say the least.

“The concept of a habitable zone is based on planets being in orbits where liquid water could exist,” said Manasvi Lingam, a Harvard University researcher who led a Center for Astrophysics (CfA) study, published in the International Journal of Astrobiology. “This is only one factor, however, in determining whether a planet is hospitable for life.”

The habitable zone around any star is the distance at which a small rocky world can orbit and receive just the right amount of heating to maintain liquid water on its hypothetical surface. Orbit too close and the water vaporizes; too far and it freezes. As life needs liquid water to evolve, seeking out exoplanets in their star’s habitable zone is a good place to start.

trappist-1-planet
The peaceful surface of a TRAPPIST-1 habitable zone exoplanet as imagined in this artist’s rendering (NASA/JPL-Caltech)

For the sun-Earth system, we live in the middle of the habitable zone, at a distance of one astronomical unit (1 AU). For a world orbiting a red dwarf like TRAPPIST-1, its orbital distance would be a fraction of that — i.e. three worlds orbit TRAPPIST-1 in the star’s habitable zone at between 2.8% and 4.5% the distance the Earth orbits the sun. This is because red dwarfs are very dim and produce meager heating — for a world to receive the same degree of heating that our planet enjoys, a red dwarf world would need to snuggle up really close to its star.

But just because TRAPPIST-1 is dim, it doesn’t mean it holds back on ultraviolet radiation. And, according to this study, the three “habitable” exoplanets in the TRAPPIST-1 system are likely anything but — they would receive disproportionate quantities of damaging ultraviolet radiation.

“Because of the onslaught by the star’s radiation, our results suggest the atmosphere on planets in the TRAPPIST-1 system would largely be destroyed,” said co-author Avi Loeb, who also works at Harvard. “This would hurt the chances of life forming or persisting.”

Life as we know it needs an atmosphere, so the erosion by UV radiation seems like a significant downer for the possible evolution of complex life.

That’s not the only bad news for our extraterrestrial life dreams around TRAPPIST-1, however. Another study carried out by the CfA and the University of Massachusetts in Lowell (and published in The Astrophysical Journal Letters) found more problems. Like the sun, TRAPPIST-1 generates stellar winds that blast energetic particles into space. As these worlds orbit the star so close, they would be sitting right next to the proverbial nozzle of a stellar blowtorch — models suggest they experience 1,000 to 100,000 times stellar wind pressure than the solar wind exerts on Earth.

And, again, that’s not good news if a planet wants to hold onto its atmosphere.

“The Earth’s magnetic field acts like a shield against the potentially damaging effects of the solar wind,” said Cecilia Garraffo of the CfA and study lead. “If Earth were much closer to the sun and subjected to the onslaught of particles like the TRAPPIST-1 star delivers, our planetary shield would fail pretty quickly.”

trappist-1-system
The TRAPPIST-1 exoplanet family. TRAPPIST-1 e, f and g are located in the system’s habitable zone (NASA/JPL-Caltech)

So it looks like TRAPPIST-1 e, f and g really take a pounding from their angry little star, but the researchers point out that it doesn’t mean we should forget red dwarfs as potential life-giving places. It’s just that life would have many more challenges to endure than we do on our comparatively peaceful place in the galaxy.

“We’re definitely not saying people should give up searching for life around red dwarf stars,” said co-author Jeremy Drake, also from CfA. “But our work and the work of our colleagues shows we should also target as many stars as possible that are more like the sun.”

Vast Magnetic Canyon Opens up on the Sun — Choppy Space Weather Incoming?

A “live” view of our sun’s corona (NASA/SDO)

As the sun dips into extremely low levels of activity before the current cycle’s “solar minimum”, a vast coronal hole has opened up in the sun’s lower atmosphere, sending a stream of fast-moving plasma our way.

To the untrained eye, this observation of the lower corona — the sun’s magnetically-dominated multi-million degree atmosphere — may look pretty dramatic. Like a vast rip in the sun’s disk, this particular coronal hole represents a huge region of “open” magnetic field lines reaching out into the solar system. Like a firehose, this open region is blasting the so-called fast solar wind in our direction and it could mean some choppy space weather is on the way.

As imaged by NASA’s Solar Dynamics Observatory today, this particular observation is sensitive to extreme ultraviolet radiation at a wavelength of 193 (19.3 nanometers) — the typical emission from a very ionized form of iron (iron-12, or FeXII) at a temperature of a million degrees Kelvin. In coronal holes, it looks as if there is little to no plasma at that temperature present, but that’s not the case; it’s just very rarefied as it’s traveling at tremendous speed and escaping into space.

The brighter regions represent closed field lines, basically big loops of magnetism that traps plasma at high density. Regions of close fieldlines cover the sun and coronal loops are known to contain hot plasma being energized by coronal heating processes.

When a coronal hole such as this rotates into view, we know that a stream of high-speed plasma is on the way and, in a few days, could have some interesting effects on Earth’s geomagnetic field. This same coronal hole made an appearance when it last rotated around the sun, generating some nice high-latitude auroras. Spaceweather.com predicts that the next stream will reach our planet on March 28th or 29th, potentially culminating in a “moderately strong” G2-class geomagnetic storm. The onset of geomagnetic storms can generate impressive auroral displays at high latitudes. Although not as dramatic as an Earth-directed coronal mass ejection or solar flare, the radiation environment in Earth orbit will no doubt increase.

The sun as seen right now by the SDO’s HMI instrument (NASA/SDO)

The sun is currently in a downward trend in activity and is expected to reach “solar minimum” by around 2019. As expected, sunspot numbers are decreasing steadily, meaning the internal magnetic dynamo of our nearest star is starting to ebb, reducing the likelihood of explosive events like flares and CMEs. This is all part of the natural 11-year cycle of our sun and, though activity is slowly ratcheting down its levels of activity, there’s still plenty of space weather action going on.

Mystery Mars Cloud: An Auroral Umbrella?

The strange cloud-like protursion above Mars' limb (around the 1 o'clock point). Credit: Wayne Jaeschke.
The strange cloud-like protursion above Mars' limb (around the 1 o'clock point). Credit: Wayne Jaeschke.

Last week, amateur astronomer Wayne Jaeschke noticed something peculiar in his observations of Mars — there appeared to be a cloud-like structure hanging above the limb of the planet.

Many theories have been put forward as to what the phenomenon could be — high altitude cloud? Dust storm? An asteroid impact plume?! — but it’s all conjecture until we can get follow-up observations. It is hoped that NASA’s Mars Odyssey satellite might be able to slew around and get a close-up view. However, it appears to be a transient event that is decreasing in size, so follow-up observations may not be possible.

For the moment, it’s looking very likely that it is some kind of short-lived atmospheric feature, and if I had to put money on it, I’d probably edge more toward the mundane — like a high-altitude cloud formation.

But there is one other possibility that immediately came to mind when I saw Jaeschke’s photograph: Could it be the effect of a magnetic umbrella?

Despite the lack of a global magnetic field like Earth’s magnetosphere, Mars does have small pockets of magnetism over its surface. When solar wind particles collide with the Earth’s magnetosphere, highly energetic particles are channeled to the poles and impact the high altitude atmosphere — aurorae are the result. On Mars, however, it’s different. Though the planet may not experience the intense “auroral oval” like its terrestrial counterpart, when the conditions are right, solar particles my hit these small pockets of magnetism. The result? Auroral umbrellas.

The physics is fairly straight forward — the discreet magnetic pockets act as bubbles, directing the charged solar particles around them in an umbrella fashion. There is limited observational evidence for these space weather features, but they should be possible.

As the sun is going through a period of unrest, amplifying the ferocity of solar storms, popping off coronal mass ejections (CMEs) and solar flares, could the cloud-like feature seen in Jaeschke’s photograph be a bright auroral umbrella? I’m additionally curious as a magnetic feature like this would be rooted in the planet’s crust and would move with the rotation of the planet. It would also be a transient event — much like an atmospheric phenomenon.

The physics may sound plausible, but it would be interesting to see what amateur astronomers think. Could such a feature appear in Mars observations?

For more information, see Jaeschke’s ExoSky website.

Want to Feel Good? Watch the Aurora Borealis in HD

The Aurora from Terje Sorgjerd on Vimeo.

I actually posted this jaw-dropping video on Discovery News last month, but today it got picked up on Digg, so I was reminded why I had to feature it.

The video is actually composed of 22,000 high-definition photographs, stitched together is a finely crafted time lapse video. The photographer in question is Terje Sorgjerd who braved -22C temperatures in the Arctic Circle to bring us this stunning perspective of the Aurora Borealis, or the Northern Lights. Throw in the Hans Zimmer “Gladiator” theme tune “Now We Are Free” and we get a timeless classic video that can be watched over and over again and never get bored.

So, sit back and enjoy the Sun-Earth interaction at its most spectacular.

For more of Sorgjerd’s work, check out his Facebook page.

Special thanks to my good friend Geir Barstein, science journalist at the Norwegian newspaper Dagbladet for originally writing about Sorgjerd’s work.

Screaming Exoplanets: Detecting Alien Magnetospheres

Exoplanets may reveal their location through radio emissions (NASA)
Exoplanets may reveal their location through radio emissions (NASA)

In 2009, I wrote about a fascinating idea: in the hunt for “Earth-like” exoplanets, perhaps we could detect the radio emissions from a distant world possessing a magnetosphere. This basically builds on the premise that planets in the solar system, including Earth, generate electromagnetic waves as space plasma interacts with their magnetospheres. In short, with the right equipment, could we “hear” the aurorae on extra-solar planets?

In the research I reviewed, the US Naval Research Laboratory scientist concluded that he believed it was possible, but the radio telescopes we have in operation aren’t sensitive enough to detect the crackle of distant aurorae. According to a new study presented at the RAS National Astronomy Meeting in Llandudno, Wales, on Monday, this feat may soon become a reality, not for “Earth-like” worlds but for “Jupiter-like” worlds.

“This is the first study to predict the radio emissions by exoplanetary systems similar to those we find at Jupiter or Saturn,” said Jonathan Nichols of the University of Leicester. “At both planets, we see radio waves associated with auroras generated by interactions with ionised gas escaping from the volcanic moons, Io and Enceladus. Our study shows that we could detect emissions from radio auroras from Jupiter-like systems orbiting at distances as far out as Pluto.”

Rather than looking for the magnetospheres of Earth-like worlds — thereby finding exoplanets that have a protective magnetosphere that could nurture alien life — Nichols is focusing on larger, Jupiter-like worlds that orbit their host stars from a distance. This is basically another tool in the exoplanet-hunters’ toolbox.

Over 500 exoplanets have been confirmed to exist around other stars, and another 1,200 plus exoplanetary candidates have been cataloged by the Kepler Space Telescope. The majority of the confirmed exoplanets were spotted using the “transit method” (when the exoplanet passes in front of its host star, thereby dimming its light for astronomers to detect) and the “wobble method” (when the exoplanet gravitationally tugs on its parent star, creating a very slight shift in the star’s position for astronomers to detect), but only exoplanets with short orbital periods have been spotted so far.

The more distant the exoplanet from its host star, the longer its orbital period. To get a positive detection, it’s easy to spot an exoplanet with an orbital period of days, weeks, months, or a couple of years, but what of the exoplanets with orbits similar to Jupiter (12 years), Saturn (30 years) or even Pluto (248 years!)? If we are looking for exoplanets with extreme orbits like Pluto’s, it would be several generations-worth of observations before we’d even get a hint that a world lives there.

“Jupiter and Saturn take 12 and 30 years respectively to orbit the Sun, so you would have to be incredibly lucky or look for a very long time to spot them by a transit or a wobble,” said Nichols.

By assessing how the radio emissions for a Jupiter-like exoplanet respond to its rotation rate, the quantity of material falling into the gas giant from an orbiting moon (akin Enceladus’ plumes of water ice and dust being channeled onto the gas giant) and the exoplanet’s orbital distance, Nichols has been able to identify the characteristics of a possible target star. The hypothetical, “aurora-active” exoplanet would be located between 1 to 50 AU from an ultraviolet-bright star and it would need to have a fast spin for the resulting magnetospheric activity to be detectable at a distance of 150 light-years from Earth.

What’s more, the brand new LOw Frequency ARray (LOFAR) radio telescope should be sensitive enough to detect aurorae on Jupiter-like exoplanets, even though the exoplanets themselves are invisible to other detection methods. Nice.

As we’re talking about exoplanets, magnetospheres and listening for radio signals, let’s throw in some alien-hunting for good measure: “In our Solar System, we have a stable system with outer gas giants and inner terrestrial planets, like Earth, where life has been able to evolve. Being able to detect Jupiter-like planets may help us find planetary systems like our own, with other planets that are capable of supporting life,” Nichols added.

Although Nichols isn’t talking about directly detecting habitable alien worlds (just that the detection of Jupiter-like exoplanets could reveal Solar System-like star systems), I think back to the 2009 research that discusses the direct detection of habitable worlds using this method: Aliens, if you’re out there, you can be as quiet as you like (to avoid predators), but the screaming radio emissions from your habitable planet’s magnetosphere will give away your location…