Earth’s fleet of satellites is in a vulnerable position. When solar activity increases, high-energy particles are directed toward Earth. Our large fleet is in the direct path of all that energy, which can damage them or render them inoperable. But now we have another tool to help us protect our satellites.Continue reading “Space Weather Forecasts can now give Satellites One Whole Day of Warning when a Killer Solar Storm is Inbound”
In 2014 , the European Space Agency’s (ESA) Rosetta spacecraft made history when it rendezvoused with Comet 67P/Churyumov-Gerasimenko. This mission would be the first of its kind, where a spacecraft intercepted a comet, followed it as it orbited the Sun, and deployed a lander to its surface. For the next two years, the orbiter would study this comet in the hopes of revealing things about the history of the Solar System.
In this time, Rosetta’s science team also directed the orbiter to look for signs of the comet’s bow shock – the boundary that forms around objects as a result of interaction with solar wind. Contrary to what they thought, a recent study has revealed that Rosetta managed to detect signs of a bow shock around the comet in its early stages. This constitutes the first time in history that the formation of a bow shock has been witnessed in our Solar System. Continue reading “Rosetta Flew Through the Bow Shock of Comet 67P Several Times During its Mission”
When it comes to exploring our Solar System, there are few missions more ambitious than those that seek to study the Sun. While NASA and other space agencies have been observing the Sun for decades, the majority of these missions were conducted in orbit around Earth. To date, the closest any mission has ever come to the Sun was with the Helios 1 and 2 probes, which studied the Sun during the 1970s from inside of Mercury’s orbit at perihelion.
NASA intends to change all that with the Parker Solar Probe, the space probe that recently launched from Cape Canaveral, which will revolutionize our understanding of the Sun by entering its atmosphere (aka. the corona). Over the next seven years, the probe will use Venus’ gravity to conduct a series of slingshots that will gradually bring it closer to the Sun than any mission in the history of spaceflight!Continue reading “The Sun is Actually One of the Most Difficult Places to Reach in the Solar System. Here’s how the Parker Solar Probe Will Do It”
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.
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.
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.
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.
Every planet in our Solar System interacts with the stream of energetic particles coming from our Sun. Often referred to as “solar wind”, these particles consist mainly of electrons, protons and alpha particles that are constantly making their way towards interstellar space. Where this stream comes into contact with a planet’s magnetosphere or atmosphere, it forms a region around them known as a “bow shock”.
These regions form in front of the planet, slowing and diverting solar wind as it moves past – much like how water is diverted around a boat. In the case of Mars, it is the planet’s ionosphere that provides the conductive environment necessary for a bow shock to form. And according to a new study by a team of European scientists, Mars’ bow shock shifts as a result of changes in the planet’s atmosphere.
The study, titled “Annual Variations in the Martian Bow Shock Location as Observed by the Mars Express Mission“, appeared in the Journal of Geophysical Letters: Space Physics. Using data from the Mars Express orbiter, the science team sought to investigate how and why the bow shock’s location varies during the course of several Martian years, and what factors are chiefly be responsible.
For many decades, astronomers have been aware that bow shocks form upstream of a planet, where interaction between solar wind and the planet causes energetic particles to slow down and gradually be diverted. Where the solar wind meets the planet’s magnetosphere or atmosphere, a sharp boundary line is formed, which them extends around the planet in a widening arc.
This is where the term bow shock comes from, owing to its distinctive shape. In the case of Mars, which does not have a global magnetic field and a rather thin atmosphere to boot (less than 1% of Earth’s atmospheric pressure at sea level), it is the electrically-charged region of the upper atmosphere (the ionosphere) that is responsible for creating the bow shock around the planet.
At the same time, Mars relatively small size, mass and gravity allows for the formation of an extended atmosphere (i.e. an exosphere). In this portion of Mars’ atmosphere, gaseous atoms and molecules escape into space and interact directly with solar wind. Over the years, this extended atmosphere and Mars’ bow shock have been observed by multiple orbiter missions, which have detected variations in the latter’s boundary.
This is believed to be caused by multiple factors, not the least of which is distance. Because Mars has an relatively eccentric orbit (0.0934 compared to Earth’s 0.0167), its distance from the Sun varies quite a bit – going from 206.7 million km (128.437 million mi; 1.3814 AU) at perihelion to 249.2 million km (154.8457 million mi; 1.666 AU) at aphelion.
When the planet is closer, the dynamic pressure of the solar wind against its atmosphere increases. However, this change in distance also coincides with increases in the amount of incoming extreme ultraviolet (EUV) solar radiation. As a result, the rate at which ions and electrons (aka. plasma) are produced in the upper atmosphere increases, causing increased thermal pressure that counteracts the incoming solar wind.
Newly-created ions within the extended atmosphere are also picked up and accelerated by the electromagnetic fields being carried by the solar wind. This has the effect of slowing it down and causing Mars’ bowshock to shift its position. All of this has been known to happen over the course of a single Martian year – which is equivalent to 686.971 Earth days or 668.5991 Martian days (sols).
However, how it behaves over longer periods of time is a question that was previously unanswered. As such, the team of European scientists consulted data obtained by the Mars Express mission over a five year period. This data was taken by the Analyser of Space Plasma and EneRgetic Atoms (ASPERA-3) Electron Spectrometer (ELS), which the team used to examine a total of 11,861 bow shock crossings.
What they found was that, on average, the bow shock is closer to Mars when it is near aphelion (8102 km), and further away at perihelion (8984 km). This works out to a variation of about 11% during the Martian year, which is pretty consistent with its eccentricity. However, the team wanted to see which (if any) of the previously-studied mechanisms was chiefly responsible for this change.
Towards this end, the team considered variations in solar wind density, the strength of the interplanetary magnetic field, and solar irradiation as primary causes – are all of which decline as the planet gets farther away from the Sun. However, what they found was that the bow shock’s location appeared more sensitive to variations in the Sun’s output of extreme UV radiation rather than to variations in solar wind itself.
The variations in bow shock distance also appeared to be related to the amount of dust in the Martian atmosphere. This increases as Mars approaches perihelion, causing the atmosphere to absorb more solar radiation and heat up. Much like how increased levels of EUV leads to an increased amount of plasma in the ionosphere and exosphere, increased amounts of dust appear to act as a buffer against solar wind.
As Benjamin Hall, a researcher at Lancaster University in the UK and the lead author of the paper, said in an ESA press release:
“Dust storms have been previously shown to interact with the upper atmosphere and ionosphere of Mars, so there may be an indirect coupling between the dust storms and bow shock location… However, we do not draw any further conclusions on how the dust storms could directly impact the location of the Martian bow shock and leave such an investigation to a future study.”
In the end, Hall and his team could not single out any one factor when addressing why Mars’ bow shock shifts over longer periods of time. “It seems likely that no single mechanism can explain our observations, but rather a combined effect of all of them,” he said. “At this point none of them can be excluded.”
Looking ahead, Hall and his colleagues hope that future missions will help shed additional light on the mechanisms behind Mars shifting bowshock. As Hall indicated, this will likely involve “”joint investigations by ESA’s Mars Express and Trace Gas Orbiter, and NASA’s MAVEN mission. Early data from MAVEN seems to confirm the trends that we discovered.”
While this is not the first analysis that sought to understand how Mars’ atmosphere interacts with solar wind, this particular analysis was based on data obtained over a much longer period of time than any previously study. In the end, the multiple missions that are currently studying Mars are revealing much about the atmospheric dynamics of this planet. A planet which, unlike Earth, has a very weak magnetic field.
What we learn in the process will go a long way towards ensuring that future exploration missions to Mars and other planets that have weak magnetic fields (like Venus and Mercury) are safe and effective. It might even assist us with the creation of permanent bases on these worlds someday!
If you’ve read enough of our articles, you know I’ve got an uneasy alliance with the Sun. Sure, it provides the energy we need for all life on Earth. But, it’s a great big ongoing thermonuclear reaction, and it’s right there! As soon as we get fusion, Sun, in like, 30 years or so, I tell you, we’ll be the ones laughing.
But to be honest, we still have so many questions about the Sun. For starters, we don’t fully understand the solar wind blasting out of the Sun. This constant wind of charged particles is constantly blowing out into space, but sometimes it’s stronger, and sometimes it’s weaker.
What are the factors that contribute to the solar wind? And as you know, these charged particles are not healthy for the human body, or for our precious electronics. In fact, the Sun occasionally releases enormous blasts that can damage our satellites and electrical grids.
How can we predict the intensity so that we can be better prepared for dangerous solar storms? Especially the Carrington-class events that might take down huge portions of our modern society.
Perhaps the biggest mystery with the Sun is the temperature of its corona. The surface of the Sun is hot, like 5,500 degrees Celsius. But if you rise up into the atmosphere of the Sun, into its corona, the temperature jumps beyond a million degrees.
The list of mysteries is long. And to start understanding what’s going on, we’ll need to get much much closer to the Sun.
Good news, NASA has a new mission in the works to do just that.
The mission is called the Parker Solar Probe. Actually, last week, it was called the Solar Probe Plus, but then NASA renamed it, and that reminded me to do a video on it.
It’s pretty normal for NASA to rename their spacecraft, usually after a dead astronomer/space scientist, like Kepler, Chandra, etc. This time, though, they renamed it for a legendary solar astronomer Eugene Parker, who developed much of our modern thinking on the Sun’s solar wind. Parker just turned 90 and this is the first time NASA has named it after someone living.
Anyway, back to the spacecraft.
The mission is due to launch in early August 2018 on a Delta IV Heavy, so we’re still more than a year away at this point. When it does, it’ll carry the spacecraft on a very unusual trajectory through the inner Solar System.
The problem is that the Sun is actually a very difficult place to reach. In fact, it’s the hardest place to get to in the entire Solar System.
Remember that the Earth is traveling around the Sun at a velocity of 30 km/s. That’s almost three times the velocity it takes to get into orbit. That’s a lot of velocity.
In order to be able to get anywhere near the Sun, the probe needs to shed velocity. And in order to do this, it’s going to use gravitational slingshots with Venus. We’ve talked about gravitational slingshots in the past, and how you can use them to speed up a spacecraft, but you can actually do the reverse.
The Parker Solar Probe will fall down into Venus’ gravity well, and give orbital velocity to Venus. This will put it on a new trajectory which takes it closer to the Sun. It’ll do a total of 7 flybys in 7 years, each of which will tweak its trajectory and shed some of that orbital momentum.
You know, trying to explain orbital maneuvering is tough. I highly recommend that you try out Kerbal Space Program. I’ve learned more about orbital mechanics by playing that game for a few months than I have in almost 2 decades of space journalism. Go ahead, try to get to the Sun, I challenge you.
Anyway, with each Venus flyby, the Parker Solar Probe will get closer and closer to the Sun, well within the orbit of Mercury. Far closer than any spacecraft has ever gotten to the Sun. At its closest point, it’ll only be 5.9 million kilometers from the Sun. Just for comparison, the Earth orbits at an average distance of about 150 million kilometers. That’s close.
And over the course of its entire mission, the spacecraft is expected to make a total of 24 complete orbits of the Sun, analyzing that plasma ball from every angle.
The orbit is also highly elliptical, which means that it’s going really really fast at its closest point. Almost 725,000 km/h.
In order to withstand the intense temperatures of being this close to the Sun, NASA has engineered the Parker Solar Probe to shed heat. It’s equipped with an 11.5 cm-thick shield made of carbon-composite. For that short time it spends really close to the Sun, the spacecraft will keep the shield up, blocking that heat from reaching the rest of its instruments.
And it’s going to get hot. We’re talking about more than 1,300 degrees Celsius, which is about 475 times as much energy as a spacecraft receives here on Earth. In the outer Solar System, the problem is that there just isn’t enough energy to power solar panels. But where Parker is going, there’s just too much energy.
Now we’ve talked about the engineering difficulties of getting a spacecraft this close to the Sun, let’s talk about the science.
The biggest question astronomers are looking to solve is, how does the corona get so hot. The surface is 5,500 Celsius. As you get farther away from the Sun, you’d expect the temperature to go down. And it certainly does once you get as far as the orbit of the Earth.
But the Sun’s corona, or its outer atmosphere, extends millions of kilometers into space. You can see it during a solar eclipse as this faint glow around the Sun. Instead of dropping, the temperature rises to more than a million degrees.
What could be causing this? There are a couple of ideas. Plasma waves pushed off the Sun could bunch up and release their heat into the corona. You could also get the crisscrossing of magnetic field lines that create mini-flares within the corona, heating it up.
The second great mystery is the solar wind, the stream of charged protons and electrons coming from the Sun. Instead of a constant blowing wind, it can go faster or slower. And when the speed changes, the contents of the wind change too.
There’s the slow wind, that goes a mere 1.1 million km/h and seems to emanate from the Sun’s equatorial regions. And then the fast wind, which seems to be coming out of coronal holes, cooler parts in the Sun’s corona, and can be going at 2.7 million km/h.
Why does the solar wind speed change? Why does its consistency change?
The Parker Solar Probe is equipped with four major instruments, each of which will gather data from the Sun and its environment.
The FIELDS experiment will measure the electric and magnetic fields and waves around the Sun. We know that much of the Sun’s behavior is driven by the complex interaction between charged plasma in the Sun. In fact, many physicists agree that magnetohydrodynamics is easily one of the most complicated fields you can get into.
Integrated Science Investigation of the Sun, or ISOIS (which I suspect needs a renaming) will measure the charged particles streaming off the Sun, during regular solar activity and during dangerous solar storms. Can we get any warning before these events occur, giving astronauts more time to protect themselves?
Wide-field Imager for Solar PRobe or WISPR is its telescope and camera. It’s going to be taking close up, high resolution images of the Sun and its corona that will blow our collective minds… I hope. I mean, if it’s just a bunch of interesting data and no pretty pictures, it’s going to be hard to make cool videos showcasing the results of the mission. You hear me NASA, we want pictures and videos. And science, sure.
And then the Solar Wind Electrons Alphas and Protons Investigation, or SWEAP, will measure type, velocity, temperature and density of particles around the Sun, to help us understand the environment around it.
One interesting side note, the spacecraft will be carrying a tiny chip on board with photos of Eugene Parker and a copy of his original 1958 paper explaining the Sun’s solar wind.
I know we’re still more than a year away from liftoff, and several years away before the science data starts pouring in. But you’ll be hearing more and more about this mission shortly, and I’m pretty excited about what it’s going to accomplish. So stay tuned, and once the science comes in, I’m sure you’ll hear plenty more about it.
Last week, ESA’s Schiaparelli lander smashed onto the surface of Mars. Apparently its descent thrusters shut off early, and instead of gently landing on the surface, it hit hard, going 300 km/h, creating a 15-meter crater on the surface of Mars.
Fortunately, the orbiter part of ExoMars mission made it safely to Mars, and will now start gathering data about the presence of methane in the Martian atmosphere. If everything goes well, this might give us compelling evidence there’s active life on Mars, right now.
It’s a shame that the lander portion of the mission crashed on the surface of Mars, but it’s certainly not surprising. In fact, so many spacecraft have gone to the galactic graveyard trying to reach Mars that normally rational scientists turn downright superstitious about the place. They call it the Mars Curse, or the Great Galactic Ghoul.
Mars eats spacecraft for breakfast. It’s not picky. It’ll eat orbiters, landers, even gentle and harmless flybys. Sometimes it kills them before they’ve even left Earth orbit.
At the time I’m writing this article in late October, 2016, Earthlings have sent a total of 55 robotic missions to Mars. Did you realize we’ve tried to hurl that much computing metal towards the Red Planet? 11 flybys, 23 orbiters, 15 landers and 6 rovers.
How’s our average? Terrible. Of all these spacecraft, only 53% have arrived safe and sound at Mars, to carry out their scientific mission. Half of all missions have failed.
Let me give you a bunch of examples.
In the early 1960s, the Soviets tried to capture the space exploration high ground to send missions to Mars. They started with the Mars 1M probes. They tried launching two of them in 1960, but neither even made it to space. Another in 1962 was destroyed too.
They got close with Mars 1 in 1962, but it failed before it reached the planet, and Mars 2MV didn’t even leave the Earth’s orbit.
Five failures, one after the other, that must have been heartbreaking. Then the Americans took a crack at it with Mariner 3, but it didn’t get into the right trajectory to reach Mars.
Finally, in 1964 the first attempt to reach Mars was successful with Mariner 4. We got a handful of blurry images from a brief flyby.
For the next decade, both the Soviets and Americans threw all kinds of hapless robots on a collision course with Mars, both orbiters and landers. There were a few successes, like Mariner 6 and 7, and Mariner 9 which went into orbit for the first time in 1971. But mostly, it was failure. The Soviets suffered 10 missions that either partially or fully failed. There were a couple of orbiters that made it safely to the Red Planet, but their lander payloads were destroyed. That sounds familiar.
Now, don’t feel too bad about the Soviets. While they were struggling to get to Mars, they were having wild success with their Venera program, orbiting and eventually landing on the surface of Venus. They even sent a few pictures back.
Finally, the Americans saw their greatest success in Mars exploration: the Viking Missions. Viking 1 and Viking 2 both consisted of an orbiter/lander combination, and both spacecraft were a complete success.
Was the Mars Curse over? Not even a little bit. During the 1990s, the Russians lost a mission, the Japanese lost a mission, and the Americans lost 3, including the Mars Observer, Mars Climate Orbiter and the Mars Polar Lander.
There were some great successes, though, like the Mars Global Surveyor and the Mars Pathfinder. You know, the one with the Sojourner Rover that’s going to save Mark Watney?
The 2000s have been good. Every single American mission has been successful, including Spirit and Opportunity, Curiosity, the Mars Reconnaissance Orbiter, and others.
But the Mars Curse just won’t leave the Europeans alone. It consumed the Russian Fobos-Grunt mission, the Beagle 2 Lander, and now, poor Schiaparelli. Of the 20 missions to Mars sent by European countries, only 4 have had partial successes, with their orbiters surviving, while their landers or rovers were smashed.
Is there something to this curse? Is there a Galactic Ghoul at Mars waiting to consume any spacecraft that dare to venture in its direction?
Flying to Mars is tricky business, and it starts with just getting off Earth. The escape velocity you need to get into low-Earth orbit is about 7.8 km/s. But if you want to go straight to Mars, you need to be going 11.3 km/s. Which means you might want a bigger rocket, more fuel, going faster, with more stages. It’s a more complicated and dangerous affair.
Your spacecraft needs to spend many months in interplanetary space, exposed to the solar winds and cosmic radiation.
Arriving at Mars is harder too. The atmosphere is very thin for aerobraking. If you’re looking to go into orbit, you need to get the trajectory exactly right or crash onto the planet or skip off and out into deep space.
And if you’re actually trying to land on Mars, it’s incredibly difficult. The atmosphere isn’t thin enough to use heatshields and parachutes like you can on Earth. And it’s too thick to let you just land with retro-rockets like they did on the Moon.
Landers need a combination of retro-rockets, parachutes, aerobraking and even airbags to make the landing. If any one of these systems fails, the spacecraft is destroyed, just like Schiaparelli.
If I was in charge of planning a human mission to Mars, I would never forget that half of all spacecraft ever sent to the Red Planet failed. The Galactic Ghoul has never tasted human flesh before. Let’s put off that first meal for as long as we can.
Remember the movie Sunshine, where astronomers learn that the Sun is dying? So a plucky team of astronauts take a nuclear bomb to the Sun, and try to jump-start it with a massive explosion. Yeah, there’s so much wrong in that movie that I don’t know where to start. So I just won’t.
Seriously, a nuclear bomb to cure a dying Sun?
Here’s the thing, the Sun is actually dying. It’s just that it’s going to take about another 5 billion years to run of fuel in its core. And when it does, Cillian Murphy won’t be able to restart it with a big nuke.
But the Sun doesn’t have to die so soon. It’s made of the same hydrogen and helium as the much less massive red dwarf stars. And these stars are expected to last for hundreds of billions and even trillions of years.
Is there anything we can do to save the Sun, or jump-start it when it runs out of fuel in the core?
First, let me explain the problem. The Sun is a main sequence star, and it measures 1.4 million kilometers across. Like ogres and onions, the Sun is made of layers.
The innermost layer is the core. That’s the region where the temperature and pressure is so great that atoms of hydrogen are mashed together so tightly they can fuse into helium. This fusion reaction is exothermic, which means that it gives off more energy than it consumes.
The excess energy is released as gamma radiation, which then makes its way through the star and out into space. The radiation pushes outward, and counteracts the inward force of gravity pulling it together. This balance creates the Sun we know and love.
Outside the core, temperatures and pressures drop to the point that fusion can no longer happen. This next region is known as the radiative zone. It’s plenty hot, and the photons of gamma radiation generated in the core of the Sun need to bounce randomly from atom to atom, maybe for hundreds of thousands of years to finally escape. But it’s not hot enough for fusion to happen.
Outside the radiative zone is the convective zone. This is where the material in the Sun is finally cool enough that it can move around like a lava lamp. Hot blobs of plasma pick up enormous heat from the radiative zone, float up to the surface of the Sun, release their heat and then sink down again.
The only fuel the Sun can use for fusion is in the core, which accounts for only 0.8% of the Sun’s volume and 34% of its mass. When it uses up that hydrogen in the core, it’ll blow off its outer layers into space and then shrink down into a white dwarf.
The radiative zone acts like a wall, preventing the mixing convective zone from reaching the solar core.
If the Sun was all convective zone, then this wouldn’t be a problem, it would be able to go on mixing its fuel, using up all its hydrogen instead of this smaller fraction. If the Sun was more like a red dwarf, it could last much longer.
In order to save the Sun, to help it last longer than the 5 billion years it has remaining, we would need some way to stir up the Sun with a gigantic mixing spoon. To get that unburned hydrogen from the radiative and convective zones down into the core.
One idea is that you could crash another star into the Sun. This would deliver fresh fuel, and mix up the Sun’s hydrogen a bit. But it would be a one time thing. You’d need to deliver a steady stream of stars to keep mixing it up. And after a while you would accumulate enough mass to create a supernova. That would be bad.
But another option would be to strip material off the Sun and create red dwarfs. Stars with less than 35% the mass of the Sun are fully convective. Which means that they don’t have a radiative zone. They fully mix all their hydrogen fuel into the core, and can last much longer.
Imagine a future civilization tearing the Sun into 3 separate stars, each of which could then last for hundreds of billions of years, putting out only 1.5% the energy of the Sun. Huddle up for warmth.
But if you want to take this to the extreme, tear the Sun into 13 separate red dwarf stars with only 7.5% the mass of the Sun. These will only put out .015% the light of the Sun, but they’ll sip away at their hydrogen for more than 10 trillion years.
But how can you get that hydrogen off the Sun? Lasers, of course. Using a concept known as stellar lifting, you could direct a powerful solar powered laser at a spot on the Sun’s surface. This would heat up the region, and generate a powerful solar wind. The Sun would be blasting its own material into space. Then you could use magnetic fields or gravity to direct the outflows and collect them into other stars. It boggles our imagination, but it would be a routine task for Type III Civilization engineers on star dismantling duty.
So don’t panic that our Sun only has a few billion years of life left. We’ve got options. Mind bendingly complicated, solar system dismantling options. But still… options.
NASA has spotted an enormous black blotch growing on the surface of the Sun. It looks eerie, but this dark region is nothing to fear, though it does signal potential disruption to satellite communications.
The dark region is called a coronal hole, an area on the surface of the Sun that is cooler and less dense than the surrounding areas. The magnetic fields in these holes are open to space, which allows high density plasma to flow out into space. The lack of plasma in these holes is what makes them appear dark. Coronal holes are the origin of high-speed solar winds, which can cause problems for satellite communications.
The images were captured by the Solar Dynamics Observatory (SDO) on July 11th. Tom Yulsman at Discover’s ImaGeo blog created a gif from several of NASA’s images.
High-speed solar winds are made up of solar particles which are travelling up to three times faster than the solar wind normally does. Though satellites are protected from the solar wind, extremes like this can still cause problems.
Coronal holes may look like a doomsday warning; an enormous black hole on the surface of our otherwise placid looking Sun is strange looking. But these holes are a part of the natural life of the Sun. And anyway, they only appear in extreme ultraviolet and x-ray wavelengths.
The holes tend to appear at the poles, due to the structure of the Sun’s magnetosphere. But when they appear in more equatorial regions of the Sun, they can cause intermittent problems, as the high-speed solar wind they generate is pointed at the Earth as the Sun rotates.
In June 2012, a coronal hole appeared that looked Big Bird from Sesame Street.
The Big Bird hole was the precursor to an extremely powerful solar storm, the most powerful one in 150 years. Daniel Baker, of the University of Colorado’s Laboratory of Atmospheric and Space Physics, said of that storm, “If it had hit, we would still be picking up the pieces.” We were fortunate that it missed us, as these enormous storms have the potential to damage power grids on the surface of the Earth.
It seems unlikely that any solar wind that reaches Earth as a result of this current coronal hole will cause any disruption to us here on Earth. But it’s not out of the question. In 1989 a solar storm struck Earth and knocked out power in the province of Quebec in Canada.
It may be that the only result of this coronal hole, and any geomagnetic storms it creates, are more vivid auroras.
Those are something everyone can appreciate and marvel at. And you don’t need an x-ray satellite to see them.
We here at Earth are fortunate that we have a viable atmosphere, one that is protected by Earth’s magnetosphere. Without this protective envelope, life on the surface would be bombarded by harmful radiation emanating from the Sun. However, Earth’s upper atmosphere is still slowly leaking, with about 90 tonnes of material a day escaping from the upper atmosphere and streaming into space.
And although astronomers have been investigating this leakage for some time, there are still many unanswered questions. For example, how much material is being lost to space, what kinds, and how does this interact with solar wind to influence our magnetic environment? Such has been the purpose of the European Space Agency’s Cluster project, a series of four identical spacecraft that have been measuring Earth’s magnetic environment for the past 15 years.
Understanding our atmosphere’s interaction with solar wind first requires that we understand how Earth’s magnetic field works. For starters, it extends from the interior of our planet (and is believed to be the result of a dynamo effect in the core), and reaches all the way out into space. This region of space, which our magnetic field exerts influence over, is known as the magnetosphere.
The inner portion of this magnetosphere is called the plasmasphere, a donut-shaped region which extends to a distance of about 20,000 km from the Earth and co-rotates with it. The magnetosphere is also flooded with charged particles and ions that get trapped inside, and then are sent bouncing back and forth along the region’s field lines.
At its forward, Sun-facing edge, the magnetosphere meets the solar wind – a stream of charged particles flowing from the Sun into space. The spot where they make contact is known as the “Bow Shock”, which is so-named because its magnetic field lines force solar wind to take on the shape of a bow as they pass over and around us.
As the solar wind passes over Earth’s magnetosphere, it comes together again behind our planet to form a magnetotail – an elongated tube which contains trapped sheets of plasma and interacting field lines. Without this protective envelope, Earth’s atmosphere would have been slowly stripped away billions of years ago, a fate that is now believed to have befallen Mars.
That being said, Earth’s magnetic field is not exactly hermetically sealed. For example, at our planet’s poles, the field lines are open, which allows solar particles to enter and fill our magnetosphere with energetic particles. This process is what is responsible for Aurora Borealis and Aurora Australis (aka. the Northern and Southern Lights).
At the same time, particles from Earth’s upper atmosphere (the ionosphere) can escape the same way, traveling up through the poles and being lost to space. Despite learning much about Earth’s magnetic fields and how plasma is formed through its interaction with various particles, much about the whole process has been unclear until quite recently.
As Arnaud Masson, ESA’s Deputy Project Scientist for the Cluster mission stated in an ESA press release:
“The question of plasma transport and atmospheric loss is relevant for both planets and stars, and is an incredibly fascinating and important topic. Understanding how atmospheric matter escapes is crucial to understanding how life can develop on a planet. The interaction between incoming and outgoing material in Earth’s magnetosphere is a hot topic at the moment; where exactly is this stuff coming from? How did it enter our patch of space?“
Given that our atmosphere contains 5 quadrillion tons of matter (that’s 5 x 1015, or 5,000,000 billion tons), a loss of 90 tons a day doesn’t amount to much. However, this number does not include the mass of “cold ions” that are regularly being added. This term is typically used to described the hydrogen ions that we now know are being lost to the magnetosphere on a regular basis (along with oxygen and helium ions).
Since hydrogen requires less energy to escape our atmosphere, the ions that are created once this hydrogen becomes part of the plasmasphere also have low energy. As a result, they have been very difficult to detect in the past. What’s more, scientists have only known about this flow of oxygen, hydrogen and helium ions – which come from the Earth’s polar regions and replenish plasma in the magnetosphere – for a few decades.
Prior to this, scientists believed that solar particles alone were responsible for plasma in Earth’s magnetosphere. But in more recent years, they have come to understand that two other sources contribute to the plasmasphere. The first are sporadic “plumes” of plasma that grow within the plasmasphere and travel outwards towards the edge of the magnetosphere, where they interact with solar wind plasma coming the other way.
The other source? The aforementioned atmospheric leakage. Whereas this consists of abundant oxygen, helium and hydrogen ions, the cold hydrogen ions appear to play the most important role. Not only do they constitute a significant amount of matter lost to space, and may play a key role in shaping our magnetic environment. What’s more, most of the satellites currently orbiting Earth are unable to detect the cold ions being added to the mix, something which Cluster is able to do.
In 2009 and in 2013, the Cluster probes were able to characterize their strength, as well as that of other sources of plasma being added to the Earth’s magnetosphere. When only the cold ions are considered, the amount of atmosphere being lost o space amounts to several thousand tons per year. In short, its like losing socks. Not a big deal, but you’d like to know where they are going, right?
This has been another area of focus for the Cluster mission, which for the last decade and a half has been attempting to explore how these ions are lost, where they come from, and the like. As Philippe Escoubet, ESA’s Project Scientist for the Cluster mission, put it:
“In essence, we need to figure out how cold plasma ends up at the magnetopause. There are a few different aspects to this; we need to know the processes involved in transporting it there, how these processes depend on the dynamic solar wind and the conditions of the magnetosphere, and where plasma is coming from in the first place – does it originate in the ionosphere, the plasmasphere, or somewhere else?“
The reasons for understanding this are clear. High energy particles, usually in the form of solar flares, can pose a threat to space-based technology. In addition, understanding how our atmosphere interacts with solar wind is also useful when it comes to space exploration in general. Consider our current efforts to locate life beyond our own planet in the Solar System. If there is one thing that decades of missions to nearby planets has taught us, it is that a planet’s atmosphere and magnetic environment are crucial in determining habitability.
Within close proximity to Earth, there are two examples of this: Mars, which has a thin atmosphere and is too cold; and Venus, who’s atmosphere is too dense and far too hot. In the outer Solar System, Saturn’s moon Titan continues to intrigue us, mainly because of the unusual atmosphere. As the only body with a nitrogen-rich atmosphere besides Earth, it is also the only known planet where liquid transfer takes place between the surface and the atmosphere – albeit with petrochemicals instead of water.
Moreover, NASA’s Juno mission will spend the next two years exploring Jupiter’s own magnetic field and atmosphere. This information will tell us much about the Solar System’s largest planet, but it is also hoped to shed some light on the history planetary formation in the Solar System.
In the past fifteen years, Cluster has been able to tell astronomers a great deal about how Earth’s atmosphere interacts with solar wind, and has helped to explore magnetic field phenomena that we have only begun to understand. And while there is much more to be learned, scientists agree that what has been uncovered so far would have been impossible without a mission like Cluster.
Further Reading: ESA