KOJO NNAMDIIf you think life on Earth is busy, you should take a look at space. There's a Rover headed to Mars equipped with a helicopter. A spacecraft is going to land on an asteroid and bring a chunk back to Earth. And don't worry if you miss this summer's media showers. There are more to be seen this year, plus a lunar eclipse.

KOJO NNAMDIWhether you already love space or you're just starting to learn about it, NASA astrophysicist Michelle Thaller is here today to guide us through the cosmos. Adults are welcome to listen, but only kids can call on Kojo for Kids. And the number is 800-433-8850. Michelle Thaller is an astrophysicist and science communicator at NASA's Goddard Space Flight Center. Michelle Thaller, thank you so much for joining us.

MICHELLE THALLERHey, it's great to be here, Kojo.

NNAMDIHelp me to correct the mistake I made in my billboard. You are a woman in astrophysics, and I misidentified you as a woman of color, because I know that's an issue that you are concerned about, that there aren't many women or people of color in the field. You think it's important that this changes.

THALLEROh, absolutely. I try to be, you know, a good ally. I'm actually serving on a couple committees at NASA about how to really grow more specifically African-American astrophysicists and space scientists all the way from, like, the middle school level and up. So, yeah, it's a big concern of ours.

NNAMDIYep, and that's, I guess, how we can make it happen, is you got to start in the middle school. Back to you. Where were you born, and where did you grow up?

THALLERI grew up in a place called Waukesha, Wisconsin which is not far from Milwaukee, Wisconsin. And so I then went to the Boston area, Cambridge, Massachusetts for college. I've lived in California. I worked at the jet propulsion laboratory. I lived in Atlanta. I got my doctorate from Georgia State University. So, I've kind of been around a little bit, but Wisconsin's still my home.

NNAMDIWhat kinds of things did you like to do as a kid?

THALLERWell, I certainly was very interested in science museums. I loved going there with my -- specifically my dad took me very often to the museums in Chicago. And Milwaukee has some excellent museums, too. I very much enjoyed the arts. You know, I wasn't a kid that just like one topic. You know, I loved history. I loved dressing up and going to renaissance fairs, you know. So, there were lots of things that I enjoyed. It wasn't just science.

NNAMDIAnd, you know, kids are calling already so let me go straight to eight-year-old Charlotte in Herndon, Virginia. Charlotte, you're on the air. Go ahead, please.

CHARLOTTEHow are stars formed?

THALLEROh, wow. That is an absolutely wonderful question, Charlotte. And, actually, I can link that a little bit to some of the things you can see in the sky, especially in the fall. So, stars are formed from giant clouds of dust and gas. Some of these clouds are actually trillions of miles across. They're just huge. And we observe stars forming in many places in our Milky Way Galaxy, which is a family of a couple hundred billion stars, all orbiting around together. And that's the Milky Way Galaxy that we live in.

THALLERIf you want to see stars forming in the sky, the best place -- just with your eye, and you don't even need a telescope, although a pair of binoculars is nice -- my favorite constellation is the constellation Orion. And Orion is a fall constellation. You see it in the fall and winter. Right now, it's rising pretty late in the night, so it'll be easier to see as the fall goes on. But, Charlotte, do you know the constellation Orion? Is that one you're familiar with?

THALLERWell, I'm sure someone can point it out to you in the sky, because you can find these three stars all sort of next to each other in the sky called the Belt of Orion. And if you go down, if you just move your eye down to the lowest of the stars, the way you see it, you'll see a glowing area which is actually an area where hundreds of new stars are being formed right now. It looks very dim to your unaided eye, just a little green smudge. But with a small telescope and even a pair of binoculars, you can see it's a glowing cloud of dust called the Orion Nebula. It's a beautiful, beautiful thing to see through a telescope.

THALLERAnd in there, there are clouds of dust and gas forming new stars. What happens is that gravity -- which wants to bring everything together, pull everything together -- gravity starts to pull on that gas and dust. And, eventually, it gets hot enough just by the crush of gravity, just by gravity crushing it all together, that it ignites a nuclear reaction and a new star turns on. And, like I said, if you can find the Orion Nebula, you can actually see a place where there are hundreds of new stars forming right now.

NNAMDIThere's a task for you, Charlotte. Thank you so much for your call. You, too, can give us a call, 800-433-8850. Do you have a favorite planet? What makes it special to you? Call if you're a kid. Michelle Thaller, you went to Harvard and decided to study astrophysics. But one of your advisers attempted to steer you away from the subject. Why did that adviser try to do that, and what made you, nevertheless, stick with it?

THALLER(laugh) Yeah, it was kind of unfortunate because when I went there -- this would've been in the late 1980s -- they assigned me a mentor who was a very famous and amazing woman astronomer named Margaret Geller. And Margaret is absolutely incredible. The generation of women who were in front of me, I think, had a much, much harder time, that they faced a lot more discrimination than I did. I mean, I certainly may have faced some, but I think they had it much harder than I did.

THALLERAnd she saw that I was, you know, a very social young woman. I was looking forward in college to studying all kind of things. I wanted to study languages and philosophy. I wanted to study history and the arts. And she didn't think I was focused enough or really driven enough to be an astronomer. And she said in years later she was sort of sorry that she said that, but she said she was trying to, in a way, be kind to me, because she didn't think I liked the intensity of being a scientist.

THALLERAnd when you think about diversity, diversity and inclusion means lots of things. And one of the things that it means is that you don't have to be a certain personality to be a scientist. That is just something left over from another age, you know, back in the Victorian era when it was pretty much only, you know, men, the very driven men that were in this.

THALLERThe idea that you have to be -- you have to work yourself to death, you have to be very, very focused, very logical, there's only one type of personality to be a scientist, that completely discounted the fact that I loved science ever since I was a little kid. And the universe doesn't care what personality you have or what age you are or what color your skin is. I mean, everybody has this curiosity, I think, at first.

THALLERAnd so it took me a while to sort of accept myself as not fitting into the stereotype of a scientist. And then that's what I tell people today. I have a lot of young people who come to me and say, you know, if I'm a scientist, do I have to work hard all the time? You know, is it always grueling? Is it always difficult? And, you know, of course, anything worth doing, there are hard parts and difficult parts. But I've loved being a scientist. So, yeah, that's the idea. She didn't think I was the right personality.

NNAMDI(laugh) Is there a distinction to be made between an astrophysicist and an astronomer?

THALLERWell, these days, professionally, the two pretty much mean the same. I think the biggest difference is that astronomer, also, to me, very, very much includes people in the amateur astronomy groups. And they may not have a formal physics degree, but they know the night sky far better than I do. You know, I'm a physicist and I studied things for my doctorate in physics that involved stars and the way stars evolve.

THALLERBut then the people who, you know, are in these amateur astronomy communities and the people who actually are just absolutely wonderful and how much they know the sky and how much they're able to sort of, you know -- they know the sky, like I said, better than I do. They're astronomers, too. So, in astrophysicists I have a degree, but the amateur astronomers often have far more experience with the sky.

NNAMDIOkay. Here we move on to 12-year-old Charlie in Washington, D.C. Charlie, you're on the air. Go ahead, please.

CHARLIECan you hear me?

NNAMDIYep, we hear you, Charlie.

THALLERYes. Hi, Charlie.

CHARLIESo, my dad told me that the universe is expanding. And I know that it's expanding into nothingness, but I don't really, like, wrap my head around what that means. Like, how can there be no, like, space or time or anything?

THALLEROh, wow, is that ever a great question. And, you know, there's some things that I'm not really able to describe very well, because, like you, you know, I look at things through a human brain, and I'm a three-dimensional creature. So, sometimes it's very difficult to visualize what these things are like. Let me start by saying, so your father's right. The universe is expanding. That was discovered about 100 years ago, by Edwin Hubble. And one of the real misconceptions about this, something that astronomers really don't like, is this idea that the universe is expanding into nothingness.

THALLERBecause the Big Bang -- you know, that's how we think the universe began, that there was this sort of -- people portray it often as a giant explosion. But when you think about explosion, you think about everything flying away from an empty center. Like, you know, if a firework goes off, right, the firework sparks go off in every direction, but away from this empty center. And that's not the way it works at all.

THALLERThe universe is full of galaxies everywhere. There is no empty center. We can see galaxies as far away as, you know, 12 billion light years away, where a light year is 6 trillion miles, the distance light travels in one year. Instead, it seems to be that it's a property of space itself. I mean, everywhere. The space, you know, right inside you, the space, you know, right inside your hands, everything, space has a property, that it seems to just expand. And, you know, we don't really understand yet why space wants to do that, but that was the discovery.

THALLERNow, lucky for us, this force is fairly gentle. So, you and I are held together by stronger forces. There are chemical bonds that hold our molecules together. There's electromagnetism that actually holds us together, as well. Gravity holds us to the Earth. We're not expanding away from the Earth right now. But out between the galaxies where there really isn't much stuff, that's where you really notice this, that all of space seems to want to expand.

THALLERSo, the galaxies are not flying off into nothingness. Instead, in every direction all at once, space itself is expanding. So, that's one thing. You know, we do wonder about are there other dimensions in space that we don't experience directly, you know, because we're three-dimensional creatures. And some modern physics ideas require that and say that there should be more dimensions that we don't know of. But as far as the expansions of the universe, you don't really need that.

THALLERInstead, think of it as just every bit of space everywhere is trying to expand. It's gentle, so, you know, the solar system is not getting bigger, because gravity holds us in an orbit around the sun. But out where there isn't anything you really notice this, and all the galaxies seem to be getting farther apart from every other galaxy in the sky. So, that's the wonderful thing about it. Everything's expanding away from everything else, and there's no empty center at all. Does that make a little more sense?

CHARLIEYeah.

THALLERYeah, so as long as you realize there's no empty center, the Big Bang was not an explosion, the way we think of it. It was a change from the universe being really, really hot and dense to it getting less dense overtime because somehow space itself wants to expand. And that's one of the biggest questions is why, or what caused the space to expand? Or what set off the big bang? Those are things we're working on right now and I hope you become an astronomer and (laugh) work on it with me because we need help.

NNAMDIThank you very much for your call, Charlie. We move on now to 11-year-old Ben, in Maryland. Ben, you're on the air. Go ahead, please.

BENI wonder what would happen if a piece of regular matter were to touch a piece of dark matter.

THALLERAh, okay. That's a great question, Ben. Okay. What would happen if a piece of regular matter touched a piece of dark matter? Well, lucky for you, you can tell me right now, because, right now, there are actually billions of, we think, dark matter particles going through you right at this second.

THALLERThere was this amazing discovery and one of the people who, you know, really got this going in the 1960s and '70s was a woman named Vera Rubin. And Vera Rubin I met a couple times, so she has since passed away, but she used to try to go work at the Mount Wilson Observatory in California. And they wouldn't let her go because there weren't any women's restrooms up there, they said. And I've worked there many nights, and we're all okay with the same restrooms, actually.

THALLERBut it's a great question. She discovered something called dark matter, that the galaxy that we live in, the Milky Way, seems to have a lot more mass than we can account for. If we add up all the stars and all the material and the gas between the stars and all the black holes, add it all up, and the Milk Way is still missing, like, 80 percent of its matter. And so we see this everywhere now in space.

THALLERSo, there's this form of matter called dark matter. And the only way we can see it is by looking for its effects. It seems to only have the property of gravity. So, we can actually watch it changing the way a galaxy rotates. And the Hubble Space Telescope has even got really good at mapping it over the entire universe, because gravity has the property of bending light. And this is what Albert Einstein showed you. And you can actually see distortions in the background light of the universe that this dark matter causes.

THALLERDark matter has gravity, and so we think that everywhere in the universe, where there's like a local strong gravity field, like the sun, the sun has a lot of gravity, we probably have a lot of dark matter around us, too. The galaxy is probably absolutely full of it. And there are filaments of dark matter that connect the galaxies together into galaxy clusters, filaments that are invisible to us except by the influence of gravity.

THALLERSo, you might be thinking of something -- if people have heard the word antimatter, and that's something different. You know, antimatter is regular matter particles that have different properties, different properties of the subatomic particles. And when matter and antimatter meet, they annihilate. They turn each other into pure energy. You know, that's sort of the Star Trek engine idea, using antimatter.

THALLERBut dark matter is right here with you in the room right now, probably billions and billions of particles of it. It just has gravity. And so, you know, we think that, you know, it's changing the way the sun orbits around the Milky Way. It changes the way the Milky Way actually flies through space and how it's joined to other galaxies. So, you are interacting with dark matter right now, but you can't touch it and you can't smell it. And there's nothing you can do except measure its gravity.

THALLERAnd so, you know, astronomers and also physicists, particular physicists that study very tiny elementary particles, we're all trying to find an example of what this dark matter really is. We're looking for it in our particle accelerators. You know, we're trying to figure out if there's more in the center of the Milky Way than there should be. We're trying to have some signals from it.

THALLERIt's really mysterious stuff, but right now, we think that it makes up, of all the matter in the universe, it makes up about 80 percent of the matter in the universe. So, you know, you and I are just kind of a little bit of dust going along on the ride above all the dark matter. So, yes, you're actually touching dark matter right now, just all it has is gravity.

NNAMDIBen, thank you so much for your call. We move on now to 11-year-old Pandora in Washington, D.C. Pandora, it's your turn.

PANDORAHello. I wanted to ask if there are aliens in space.

THALLERHi, Pandora, that's a great question.

NNAMDIAre there aliens in space? (laugh)

THALLERDid you say aliens in space, right?

NNAMDIYes.

PANDORAYes.

THALLERYes. Okay. Yeah, so this is a big deal at NASA. We would really, really love to find evidence of life outside the Earth. This is one of our major science goals. And the answer right now, you know, as of this moment, is we don't know. We have never found evidence strong enough that we could say absolutely we have detected life outside the Earth. But I think there most likely is. And I think most astronomers would agree with me that, when you think about how many stars in our one galaxy, hundreds of billions of stars, and almost every star seems to have its own solar system.

THALLERSo, you know, in our galaxy alone, hundreds of billions of planets and then, of course, you know, with the Hubble Space Telescope, we can actually see, with enough time, trillions of galaxies. So, there must be life out there. There are places in our own solar system that we think might be friendly environments for life. And one of our big goals in the next couple of years is to send more spacecraft out there to study this. So, my favorite place is to look for life.

THALLERThere are two moons in the outer solar system that have oceans of warm salt water that are protected by a shell of ice. One is a moon of Jupiter called Europa. And underneath the icy crust of Europa, there is more liquid water than on Earth, more liquid water. And there's a moon of Saturn called Enceladus, which is much the same.

THALLERIn the case of Enceladus, the ice is cracking along the south pole and water is gushing out, turning into icy, frozen water vapor as it goes into space. And the Cassini spacecraft, which spent about 15 years around Saturn, actually flew through these plumes of ice crystals, and we detected the presence of organic molecules, which is the same kind of chemistry that you and I have.

THALLERThere's another moon of Saturn called Titan. Titan is huge. Titan means a really big giant. Titan is nearly the size of the planet Mars. It has a thick atmosphere, and it's raining right now on Titan. There's rain and rivers, and there are lakes that we see. All of that rain and the lakes are made of actually liquid methane, liquid natural gas. And we think that there could be life there, based not so much on water, but on methane.

THALLERWe also are looking for life on Mars. We just sent the Mars Perseverance Rover to join the Mars Curiosity Rover. And they both look for signs of life. Mars once had oceans like the Earth. It was much more Earth-like and friendly to life, you know, hundreds of millions of years ago. So, what I want to have happen is I want your question to be answered in my lifetime. I would really love to have strong scientific proof that there's life outside the Earth. Even if it's a tiny little germ, a little bacteria-like thing, I think that's amazing.

THALLERBecause we'll be able to ask questions like, does it have DNA like we do? Is it very similar to us? Is it very different to us? So, you know, again, this is one of the questions I would love to answer. It's a great question. I hope I'm going to answer it pretty soon. (laugh) Thank you, Pandora.

NNAMDIThank you so much -- thank you so much for asking it, Pandora. Here is six-year-old Beatrice. Beatrice, it's your turn.

BEATRICEHi.

THALLERHi.

BEATRICEHow are black holes made?

THALLEROh, that's a great question. I love black holes. So, easily put, there are different kinds of black holes. Some are only a couple times the mass of the sun, and those are small ones. That seems like a silly thing to say, right. Basically, it's something that's several times the mass of our sun, but that's a small one. And those are formed when stars that are bigger than our sun actually have more mass, maybe like, you know, five or more times the mass of our sun. When they die, they actually collapse violently, that the core of the star used to be really hot, because all of these wonderful nuclear reactions were going on. That's what makes a star shine.

THALLERWhen those go out, and they all do, stars die, just like everything else. They're born, they live a lifetime, and then they die. And when these big stars die, the core turns off. There's no more energy, and the whole star collapses in on itself. And that forms such a density of gravity, so much gravity, that it's actually able to bend space and time itself. It basically closes off this area, bending space and time back on itself and nothing can get out.

THALLERAnd it's amazing to think that nothing can get out, not even light. But the reason is that, you know, space itself are bent in. That's just an incredible idea. That idea is a hundred years old. You know, it goes back to Albert Einstein. But we observe many black holes. We observe relatively small ones. We observe ones being formed. There was a star recently that the Hubble Space Telescope saw it just disappear. It was this big star, and it didn't even explode. It just collapsed and we think that's because it formed a black hole when it died.

THALLERBut then black holes that are much bigger than that. You and I are actually spinning around a black hole right now at about half a million miles an hour. And that black hole is in the very heart of our galaxy, the Milky Way galaxy. And that black hole is about 4 million times the mass of the sun all squeezed together.

THALLERAnd then some of them get even bigger than that. There's a wonderful picture that was done a little more than a year ago, where you could actually see the black part where light is actually getting sucked into a big black hole in another galaxy far away. The galaxy's called M87, and that black hole, we think, is about 5 billion times the mass of the sun. It's really relatively small. You could fit all of that inside our own solar system, 5 billion times the mass of our sun.

THALLERNow, these smaller black holes, you know, we see these being formed when stars die. The really, really big ones, billions of times the mass of the sun, we're not entirely sure exactly how they do form. Because one of the things that's sort of crazy is that we see these things very far away in space. So far away that the light took a long time to get to us. Light travels at 186,000 miles per second.

NNAMDIOnly have about a minute left, but go ahead, please.

THALLEROkay, right. So -- but even at that speed it took billions of years to get to us. So, there are these giant black holes way far away in the universe, and they formed way back in time. And those, we're not really sure how they formed yet.

NNAMDIAnd so thank you very much for your call, Beatrice. And, Michelle Thaller, thank you very much for joining us and for your time.

THALLERIt's been wonderful. Thank you so much, Kojo.

NNAMDIMichelle Thaller's an astrophysicist and science communicator at NASA's Goddard Space Flight Center. Kojo for Kids with NASA astrophysicist Michelle Thaller was produced by Lauren Markoe. And our conversation about postal problems in the election was produced by Richard Cunningham. Coming up tomorrow, in June, D.C.'s mayor commissioned a local muralist to paint Black Lives Matter in 35' high letters leading up to the White House and renamed the space Black Lives Matter Plaza.

NNAMDISince then, Black Lives Matter Plaza has taken on a life of its own. We'll talk about what the space means to local Washingtonians and how it will be used in the years to come. That all starts tomorrow, at noon. Until then, thank you for listening and stay safe. I'm Kojo Nnamdi.