NASA's Curious Universe - Plasma, Plasma, Everywhere!

Episode Date: August 9, 2021

The night sky is full of planets, satellites, and cosmic objects we can see with our eyes and telescopes. In between all that material there’s a huge amount of invisible matter and the vast majority of it is called plasma. Follow along with scientists Doug Rowland and Don Gurnett, as we journey through this mysterious and electrifying substance.

We think of space as being empty. And I don't mean like planets and stars. Of course, those things are out there. Even the space between the planets and the stars is full and it's rich and it's dynamic. You get all these different charged particles of the gas, the plasma. You get electric and magnetic fields. You get radiation. You get dust.

You know, you get all these different things up there. And yeah, they're so rarefied that you don't see it from the ground with your eye. There's this big invisible population. So space being empty is the biggest misconception, I think. It's just full and it's important and it's interesting. Just so many things that if we could see them, they'd be on the wall of every art museum. I mean, they are just glorious some of these things. This is NASA's curious universe.

Our universe is a wild and wonderful place. I'm Patty Boyd, and in this podcast, NASA is your tour guide. you're probably familiar with three states of matter, solids, liquids, and gases, like ice, water, and steam. Beyond gases, there's another state of matter, called plasma. And it makes up 99.9% of the observable universe. This is completely different from plasma in our blood. We're talking about a state of matter that's similar to a gas, but with different properties. We actually don't see this kind of plasma very often on Earth.

But when we do, it can be in beautiful and exciting ways. So what is this substance that is so common in our cosmos, but still puzzling scientists here on our home planet? Today, we are taking you on a tour of plasma, what it is and where we can find it. But before we get out in the world, the expanses of space, we have to start really, really small. My name is Don Gernett.

I'm an emeritus professor at the University of Ohio Department of Physics and Astronomy, where I've worked for something close to 65 years. I've been other places in between, though. Don Gernett has spent his career studying plasmas and plasma physics. To begin talking about plasmas, you have to start with a gas. And to turn that gas into a plasma, we've got to add a little bit of energy. On Earth's surface, we don't have any significant plasma. We have neutral gas, thankfully, because plasma would probably cause you health problems. Like all states of matter, a plasma is made up of atoms or molecules that have been excited with energy.

Those atoms are made up of three different particles. Neutrons, protons and electrons. In a neutral state, an atom or molecule has the same number of positively charged protons as negatively charged electrons. If you could strip the electron off of the atom so that the electrons are free, then you have electrons and positive ions. That's called a plasma. So you might ask the question, how do you strip the electron off of the atom?

there's at least two ways that I'll mention. One is to heat the gas up to a very high temperature, so high that the vibration of the molecules will break off an electron. And that happens when you get a ordinary gas to a high temperature, like in a flame. If you get up to like 1,500 or 2,000 degrees, there'll be a bit of a plasma there. Under more extreme circumstances, like an electric arc welder, you know, which makes a big spark, Well, that's a plasma, actually. While most plasma is found out in space,

there are a few instances where you can find it right here on Earth. Some of them you probably see every day, and others are more of a rare occurrence. On a daily basis, you can find plasma in fluorescent light bulbs, plasma screen TVs, and neon signs, but these are pretty small and contained cases. We don't start to see bigger instances of plasma until we head up into the Earth's atmosphere. When a lightning discharge occurs, you know, you see that flash across the sky.

Well, that flash is caused by an electrical current, which heats the ordinary gas up to a very high temperature and makes a plasma calm, which is glows, and that's what you see is the lightning flash. that example tells you another important thing about a plasma compared to an ordinary neutral gas. A plasma conducts electricity, and that's what makes a plasma really different from an ordinary gas. It involves electricity and magnetism effects. It might be hard to conceptualize a plasma because we don't interact with them very often compared to a solid, liquid, or gas. But a plasma is very similar to a gas, until you start looking at a plasma. looking at the magnetic or electric principles.

This can make for some pretty strange effects and some pretty complicated science. Electric and magnetic fields are all around us, but they don't typically affect solids, liquids, and gases we interact with. They do shape plasma. And the further we start to get away from Earth's relatively neutral surface, the more often we can find these electrically charged gases. Hi, I'm Doug Rowland and I'm a scientist studying the Earth's upper atmosphere and that's an interesting region because it's where the Earth's atmosphere that we breathe turns into

a gas called plasma that's electrically charged. Doug studies the layers of gases in our Earth's atmosphere as we move out towards space. So once we get beyond our lightning and the things that happen right here on the ground, the first plasma you encounter would be something like 50 miles over here. head and it's different during the day and at night. During the day there be plasma at those altitudes and that's generated as the sunlight shines on that gas. It's a very tenuous gas so the sunlight shines on the ultraviolet light breaks those atoms apart. At night there's no sunlight so depending on where you are in the

world there's no other source of ionization so at night you wouldn't see plasma that one of the reasons plasma doesn't last long here on Earth is because those those atoms generally stay in their neutral form, and ions and electrons quickly come back together if they have been separated. However, with stronger forces from the Sun and fewer particles in our upper atmosphere, the ions and electrons don't come back together as quickly, resulting in an extended state of plasma. As you go up in altitude, the plasma can last for longer.

So once you generate it with the sun shining on it, once you get up to say 100 miles or 200 miles, that plasma can live for a long time. So even after that part of the Earth's atmosphere rotates into the night side, you can persist for a long time. There's another way plasmus can be formed, besides separating atoms or molecules, and that's by adding extra electrons to a neutral gas. You can also create plasma by slamming into them with other particles like electrons. And the way the aurora created is you get electrons coming in from outer space and they get shot down out of outer space into the atmosphere.

The aurora, which you might know as the northern lights or southern lights, are beautiful displays of light in the night sky. These shifting sheets of light and color in our Earth's atmosphere appear mostly near the North and South Poles. They can come in a wide variety of shapes and colors, and they happen when electrons from space collide with atoms in the Earth's atmosphere. And when they do that, they run into gas molecules, gas atoms depending on what are they And they can do two things.

They can excite those atoms or molecules and make them emit light, like red light or green light, like you might see in the aurora. And they can also sometimes break those atoms or molecules apart and make ions and electrons. The beautiful aurora are a visual side effect of some of the particles in Earth's atmosphere turning from a neutral gas into a plasma. But seeing the aurora isn't the only way we can experience a plasma.

I have gotten into kind of an unusual area of research, and that is to study waves in plasma. Again, this is Professor Don Gernett. You see, I'm talking here sound waves. That's the way I'm speaking. Plasma also has, it turns out, a wide variety of waves that can propagate in a plasma. We call them plasma waves. Since his time as an undergraduate at the University of Iowa, Don has been studying all the different ways we can hear plasma. And way back in like 1961, we had a visitor to come here and play some unusual sounds that they detected on the ground, things called Whistlers. And I got very interested in this, and I decided to build just down in the,

the basement of the physics building just for fun. I was an undergraduate engineering student then and I built this receiver to try to detect these these radio waves from space that people didn't know much about. Couldn't use it around the city because the city has so much 60-hertz power line noise. So I took my receiver out to my father's farm and we turned all the electricity off. And at first I I remember I was disappointed because I didn't hear anything, but just kind of a hissy noise, which is the noise of the receiver. But then I think it was on the third night I heard very distinctly.

I can't mimic that very well, but that's what it sounded like. So this was really exciting, not only to me, but a lot of people. And there are a lot of different things we can hear once we pick up sounds of plasma waves, including whistlers, hisses, and choruses. This is a whistler wave. Sounds pretty spacey, right? If you've got the right antenna out, you can hear those around lightning strikes.

A chorus wave happens when loose electrons hit a plasma. And a hiss? Not yet sure what exactly causes a hiss, but it could be similar to a whistler wave or a chorus wave. Analyzing sounds can help scientists better understand the different ways plasma behaves. There's still a lot to learn about this mysterious substance,

especially when you think about how much there is out in the observable universe. So it turns out that almost everything in our universe above an atmosphere altitude of about 100 kilometers is a plasma. Some people estimate that 99.9% of everything in the universe is a plasma. As we continue out on our plasma journey, the most significant source of plasma in our solar system is the sun.

The sun is very hot, and it's a plasma. Stars, like our sun, are made of very hot gases. The sun is so hot that most of its gas has been, been ionized into a plasma. When those plasma particles leave the sun and head out in all directions into space, we call that solar wind. And we now know that every planet in our solar system encounters some of that plasma. We must talk about Voyager.

In the late summer of 1977, two unmanned spacecraft, Voyager 1 and 2, lifted off from Cape Canaveral atop Titan-Sentaur rockets. The Voyager 1 and 2 spacecraft were launched in 1977 and have explored further into space than anything else we've sent out into the universe. Traveling uninterrupted through interstellar space, the voyagers will endure forever. Long after everything man has ever built has crumbled into dust. The Voyagers journeyed to the furthest planets in our solar system. They were also the first objects to go beyond the boundary of interstellar space.

where the plasma from our sun gives way to the plasma that fills the spaces between the stars. Well, we flew by with Voyager with a plasma wave instrument for the first time. We flew by Jupiter, Saturn, Uranus, and Neptune with Voyager 2. Voyager 1 only went to Jupiter and Saturn. At those flybys, we detected many of the same things that we detected at Earth.

That was the first evidence of lightning at a planet other than Earth. So we now know that plasmas can be found in Earth's atmosphere, the sun, and the lightning strikes of other planets. But where is this 99.9% figure coming from? You have to remember that space is really big, and so much of our universe isn't made up of planets or stars, but is the really, really vast spaces in between those objects. Most of interstellar space, the space between solar systems, is full of hydrogen and helium plasmas. These interstellar plasmas are the result of exploded giant stars millions of years ago. Overall, plasmas make up more matter than all of the solids, liquids, and gases in our universe

combined. It's fascinating to look into the night sky and remember that the stars and the spaces between them are mostly made of this wild and energetic substance. Here on Earth, we're surrounded by solids, liquids, and gases, and on a much larger scale, we're actually surrounded by plasmas. Our journey through this fascinating fourth state of matter started at some of the smallest particles and ends with the vastest distances in our universe. And isn't it wonderful that there's still so much to learn? This is NASA's Curious Universe. This episode was written and produced by Christina Dana.

Our executive producer is Katie Atkinson. The Curious Universe team includes Maddie Arnold, Kate Steiner, and Michaela Sosby, with support from Emma Edmund and Priya Mettal. Our theme song was composed by Matt Russo and Andrew Santaguita of System Sounds. Special thanks to Calla Cofield, Sarah Frazier, Miles Hatfield, Rylind Heggy, Joy Eng, Nick Tom Lonovic, Lena Tran, and the Heliophysics team. If you liked this episode, please let us know by leaving us a review, tweeting about the show at NASA, and sharing NASA's curious universe with a friend.

Learn more about plasma and heliophysics. by visiting science.nasa.gov slash heliophysics. Still curious about NASA? You can send us questions about this episode or a previous one, and we'll try to track down the answers. You can email a voice recording or send a written note to NASA-curiousuniverse at mail.nastna.gov. Go to nassah.gov slash curious universe for more information.

Well, my dad was an engineer back in the day, and he was always building things. they were kind of very concrete things. Like we built a TV antenna for our house. We get television back in the day before cable. We built things like that. And when I went to college, I said, well, I'm going to do something technical. I wasn't sure.

I heard that a summer internship program was opening up for a team that was doing balloon research. And this was a group that was doing astronomy. I said, astronomy, what does that have to do with balloons? And it turned out they were doing gammaery astronomy. And they developed a new kind of camera that could take pictures of the universe and camera rays and they flew it on this gigantic balloons out of Fort Sumner, New Mexico. And they needed a roadie. And I said, I'm going to be the roadie. I'm going to go along and drive the truck basically for them and carry all their stuff. It was really fun because

he got to see kind of a small group of people who were really dedicated, really excited about something, working really closely together at a high level of performance and just having that camaraderie and that. So it's really the people that attracted me, not the science per se.