How Do You Science | Meet a Black Hole Scientist

I learned all about black holes from WSU observational astrophysicist Vivienne Baldassare. 

• Check out Dr. Baldassare's favorite black hole
• Learn more about galaxies, black holes, and exoplanets from NASA
• Peep the Vera C. Rubin Observatory in Chile
• Explore the NASA exoplanet database
• Dig into NASA's search for life outside our universe

 As always, submit burning questions at askdruniverse.wsu.edu.  Who knows where your questions will take us next.

Transcript

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Dr. Universe: Hey friends, I'm Dr. Universe. And if you're anything like me, you've got lots of big questions about our world. Today I'm talking with Vivienne Baldassare, an astrophysicist at Washington State University. She studies black holes. I can't wait for you to hear all about it. Let's get started. 

So, you are an observational astrophysicist. What does that mean? 

Vivienne Baldassare: It means that I work with observations from telescopes on the ground and in space to study different aspects of the universe. 

Dr. Universe: What does an observation look like? 

Vivienne Baldassare: It can look like a lot of different things. And we take all different kinds of observations—from observations using X-ray telescopes to observations that collect images similar to what we might see with our eyes. But sometimes an observation is just a picture of a galaxy or a star in a particular wavelength of light. 

Dr. Universe: Does an image from an X-ray telescope look like an X-ray? Like when you get your arm broken? 

Vivienne Baldassare: No. They actually are not very exciting looking. So they tend to be fairly low resolution. And the X-ray images that I work with, where we're trying to detect X-rays from around massive black holes, just look like basically little dots of light. So, they're not very exciting. 

Dr. Universe: So, you specifically study black holes? 

Vivienne Baldassare: Yes. 

Dr. Universe: What is a black hole? 

Vivienne Baldassare: I like to think of a black hole as an object that is so dense, even if you could jump away from it at the speed of light, you would always fall back down. 

So, every object has an escape speed, which is the speed that you would need to jump off of its surface in order for its gravity not to tug you back down. 

Dr. Universe: That's like how when they took the Artemis 2, they had to go with the rocket looking thing to escape Earth's gravity?

Vivienne Baldassare: Yeah, that's exactly the same concept. So, for Artemis two, they didn't quite exceed the escape speed of Earth, since they weren't trying to get very far away from it. But for missions that are leaving the Earth—maybe they're going to Mars or the outer solar system—they would have to exceed the Earth's escape speed in order to not come back to Earth. 

And so, for a black hole, that escape speed is the speed of light. And so nothing can move faster than the speed of light. So, nothing can get away from a black hole. 

Dr. Universe: And the reason that it's so suck-y is just because it's big or heavy?

Vivienne Baldassare: Black holes are very dense. So you have a lot of matter that is packed into a very small space. And black holes aren't necessarily sucking in everything. It's just that if you happen to get close enough to it, then you will eventually fall into the black hole.

Dr. Universe: Which would be bad. 

Vivienne Baldassare: Yes, it would be bad. 

Dr. Universe: Kids are always asking me what would happen if you fell in. 

Vivienne Baldassare: Yeah, it's a very intense gravitational field close to a black hole. So, unfortunately, you would actually get kind of stretched apart as you got close enough. It wouldn’t be a good place to go visit, but we don't have anything to fear because there are no black holes that are close enough to us to be a concern. 

Dr. Universe: Such a relief. So, you study really, really big black holes. Is that right? 

Vivienne Baldassare: I study a particular kind of black hole that is the smallest of the big black holes. We kind of observe black holes in two different classes. We see black holes that are a few times the mass of the sun. And those are all over our galaxy. And then we have supermassive black holes that are millions or billions of times the mass of the sun. And I look for black holes that are in between those two classes. So, kind of the smallest of the big black holes. 

Dr. Universe: It's really hard to imagine something that is a billion times the size of the sun. 

Vivienne Baldassare: It is. There are some galaxies that are smaller than black holes that are a billion times the mass of the sun. It's impossible to grasp something of that magnitude. 

Dr. Universe: How does a black hole get there? Have they always been there? 

Vivienne Baldassare: Great question. And that's something that my research is trying to address—how do these supermassive black holes form? And we kind of don't know whether they start off small when really big stars die. That's how we know the little black holes form. 

So, the supermassive black holes could start off small and then have to do a lot of growing, have to eat a lot of stuff to reach the supermassive black hole size. Or there could be special conditions that occur in the early universe that allow black holes at that time to form much bigger, and then they wouldn't have to necessarily grow as much to reach the supermassive sizes that we observe. 

Dr. Universe: If something gets close enough to the black hole that it can't escape from the black hole, does the black hole become that much bigger? 

Vivienne Baldassare: Yes. The matter that falls into a black hole will then contribute towards the overall mass. And black holes can grow in two different ways. They can either consume material. So you'll have sometimes a disk of gas that's swirling around the black hole and falling in over time. And then black holes can also actually merge with other black holes and grow that way. So, we have kind of those two ways for a black hole to grow. 

Dr. Universe: Do they last forever? 

Vivienne Baldassare: So, there are some theories that suggest black holes may evaporate very slowly over time. This is called Hawking radiation after Stephen Hawking, and basically suggests that black holes will very, very slowly release energy. 

But if this is happening, then the time scale for this to happen would be much longer than the age of the universe for the types of black holes that we observe. So theoretically, black holes could evaporate over time, but we haven't observed this. And if it were happening, it would take so long that it wouldn't really be relevant to us. So, for our purposes, if there's a black hole there, it's going to stick around. 

Dr. Universe: What is your favorite thing about black holes? 

Vivienne Baldassare: I love the idea of searching for something by looking for the influence that it has on the material around it, because we will never know what's going on inside of a black hole. And to study them, we have to look at the impact that a black hole has on the stars or the gas in its immediate vicinity. 

And so, it's kind of like putting together a little puzzle, trying to figure out where a black hole might be, and figure out what we can learn about it by looking at its impact on its surroundings. I find that really exciting. 

Dr. Universe: Is that because the light can't escape? So, it's not like it's shining or something, right? 

Vivienne Baldassare: Nothing can leave the black hole because again, the escape speed is the speed of light. And nothing in our universe can move faster than the speed of light. So, nothing—even information, a communication signal, nothing—would ever be able to leave the black hole. And if somehow we were able to send something into a black hole, we would never be able to get the information out, so we can't know what's going on inside. And so, in order to learn about them, we just have to look at the impact that they have on the stuff around them. 

Dr. Universe: What kind of clues do you look for? 

Vivienne Baldassare: Yeah. I look for the signature of gas that is swirling around the black hole. So, when you have a black hole that is consuming a lot of material very quickly, that material will collect in a disk around the black hole and will swirl into the black hole over time. And those disks are really bright and really hot. And they're also fairly turbulent. And so, I look for light from these disks. And that light from the disk, because the disk is so turbulent, will vary over time in a characteristic way. And if you take many, many images of the same galaxy over a year or many years, you can actually detect those little variations from the disc that is feeding the black hole in the galaxy. And so that's what I look for. 

Dr. Universe: How do you tell the size of the black hole to know if it's one of your black holes or not? 

Vivienne Baldassare: That's a great question. So, we think that the time scale of that variability—so how fast or how slow those variations occur—is related to the mass of the black hole. And it gets very tricky because the smaller the black hole, the faster that variability is. 

And so, you need to take maybe multiple observations of the same galaxy per night or every night. And so you really need to be diligent with your observations and collect a lot of data for those systems to be able to say whether there's one of these small supermassive black holes. 

Dr. Universe: What does your day as an astrophysicist look like? 

Vivienne Baldassare: I do a lot of different things. So, any day there will be a combination of analyzing data, writing a proposal for a telescope to collect new observations, working with my students who all have different projects related to studying black holes. And then also preparing for and teaching the courses that I teach. 

Dr. Universe: When you're looking at data, is that like sitting at a computer and looking at numbers or pictures? 

Vivienne Baldassare: Yeah, it's usually taking the images or the observations that we make. Sometimes you need to do some work basically to calibrate them and get them ready to make scientific measurements. And then actually a lot of coding to extract information from those observations and be able to draw conclusions. 

Dr. Universe: What is your favorite part of your job? 

Vivienne Baldassare: My favorite part of my job is definitely working with data and trying to make new discoveries and piece together little puzzles for each galaxy of whether there's a black hole there. I love pulling together different pieces of evidence to try to make these discoveries of these small supermassive black holes. And then using those to try to inform our overall understanding of how black holes form and grow. I find that all really fun. 

Dr. Universe: Do you have a favorite black hole? 

Vivienne Baldassare: I do, actually. When I was a graduate student, I made a discovery of a black hole that is 50 thousand times the mass of the sun. And at the time, this was the smallest supermassive black hole that had ever been discovered. It's in a galaxy called RGG 118. And since then, there have been a couple of similar sized black holes that have been discovered—but that one holds a special place in my heart. 

Dr. Universe: Do you get to name them when you discover them? 

Vivienne Baldassare: No. They're usually named based on some catalogue of galaxies, and often there's numbers that are related to the position of the galaxy on the sky. So no, I did not get to name it. 

Dr. Universe: How does it feel to discover something like that? 

Vivenne Baldassare: It's incredibly rewarding. And I can remember sitting at my computer—and I happened to be working late at home because I was so excited about this particular system—and programming and realizing what I had found. And having a really special moment where you realize that you've discovered something that no one else has seen before and getting to really treasure that for a moment before sharing it with the rest of the world. 

Dr. Universe: Did you always know you wanted to be an astrophysicist? 

Vivienne Baldassare: No. It came kind of later on for me. I knew that I loved physics and math in high school. But it wasn't until I was in college, and I had the opportunity to do some research with a professor at my undergraduate institution in astronomy, that I considered that this was a career possibility for me. But ever since that experience, I have been hooked. And so, it was a really fortunate undergraduate research experience that led me on this path. 

Dr. Universe: Did you always know you wanted to be a scientist? 

Vivienne Baldassare: I think I was always drawn to more scientific careers, although my dream growing up was to be a veterinarian. I am still very passionate about animals, so that was kind of my childhood dream. So I've always been excited by math and science. 

Dr. Universe: Now you're a doctor for black holes instead of kittens. If you had any advice for a kid who wants a cool job like yours someday, what's your advice? 

Vivienne Baldassare: I would just say to stay curious and ask questions about everything that you can—everything that you're even a little interested in or makes you go, “Hmm, I wonder what that could be.” Just observe the world around you and ask lots of questions, and you never know where that might lead you. 

Dr. Universe: I think sometimes we think of black holes as kind of like scary. Do you find them scary? Like the idea of a black hole? 

Vivienne Baldassare: I don't find them scary. I do find them mysterious. And it's a really interesting idea, I think, that there are places in the universe that will never be accessible to us—that there's things that, on some level, we will never understand. But I also think that there's something kind of beautiful about that. That we can't know everything, and that's okay. We can still study them. We can learn what we're able to and kind of accept that there are things we won't know. 

Dr. Universe: I love that so much, especially now. It feels like information is like right there. You can get an answer really, really fast. It's kind of cool to think there's a place we're never going to visit or really get. 

Vivienne Baldassare: Yeah, yeah, it is. 

Dr. Universe: I would love to know about new telescopes and new discoveries. 

Vivienne Baldassare: Yeah. There's a new telescope that I'm extremely excited about called the Vera Rubin Observatory. This is a new telescope in Chile that is going to take images of the entire visible night sky every three nights. And so, this telescope is specially designed to study things that change, or transients or things that move in the night sky.

And so, this is perfect for the kind of work that I do where we're looking for these little variations over time. So, I'm really excited about this new telescope, which is operating and starting to collect data now. And hopefully we'll have exciting new results in the next couple of years from this telescope. 

Dr. Universe: Is astronomy the kind of thing where people share a lot of their telescopes and data and all of that. 

Vivienne Baldassare: Yeah, that's a great question. There are some telescopes where you'll apply for time and are awarded time to take your observation. But there are also a lot of telescopes that are more like shared facilities. And these might be nationally funded. And then they take data, and they make them available to the entire community and to the public. And so there's a really nice balance of both types of facilities, and I work with both types of data. And it's really great. 

Dr. Universe: What's your favorite resource like that that a kid could go and look at if they wanted to see some stuff?

Vivienne Baldassare: All of the NASA missions have amazing websites where you can look at recent discoveries. And one of the cool resources I've been looking at lately for my class is the NASA exoplanet database, where they post all of their new exoplanets. These are planets outside of our solar system that have been discovered and all the properties of each planet. And that's so much fun to be able to see what other worlds are out there. 

Dr. Universe: I have to ask: do you think there's intelligent life out there other than us? 

Vivienne Baldassare: Great question. I would say I feel like it's likely just because one of the things we've learned in the last 5 to 10 years is that we think every star has at least one planet. And there are hundreds of billions of stars in our galaxy. There are hundreds of billions of galaxies. And it's hard for me to think that in all of those worlds that there wouldn't be intelligent life somewhere else. Do I think that we will find it? Probably not in my lifetime. But I do think that there is life. 

Dr. Universe: That's all for this episode, friends. Big thanks to Vivienne Baldassare for this window into black holes. 

As always, if you've got a science question for me, you can submit it at askdruniverse.wsu.edu. That's A S K D R U N I V E R S E dot W S U dot E D U. 

Who knows where your questions will take us next?