Dean chats with Dr. Gerard van Belle a tenured astronomer and the director of science at the Lowell Observatory in Flagstaff, Arizona. Listen to find out how the star Altair got its "oddball" shape.
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Additional resources referenced in this episode:
- Altair, spinning animation
- Imaging The Surface Of Altair
- Meet an Astronomer | First Light for the QWSSI Instrument with Dr. Gerard van Belle
Episode Transcript:
Looking Up is transcribed using a combination of AI speech recognition and human editors. It may contain errors. Please check the corresponding audio before quoting in print.
Dean Regas: In the movie from the year 2000 called Pitch Black, Vin Diesel and a miscellaneous crew crashed land on a mysterious planet. They quickly learn some astronomy and as the planet has six suns in the sky, one by one, the suns start to set. It gets darker and darker. Until finally all six suns are gone from the sky and plunges them into pitch blackness,
[Pitch Black Movie Audio]: …A total eclipse, we're gonna lose everybody out here.
Dean Regas: So is there really a planet like this? Is there a place with four, five, or even six suns in the sky?
[Pitch Black Movie Audio]: You can't leave. Gotta say goodnight.
Dean Regas: From the studios of Cincinnati Public Radio, I'm your host, Dean Riga, and this is Looking Up, the show that takes you deep into the cosmos or just to the telescope in your backyard, to learn more about what makes this amazing universe of ours, so great. My guest today is Dr. Gerard van Belle, a tenured astronomer and the director of science at the Lowell Observatory in Flagstaff, Arizona.
So is there really like a planet like Pitch Black with six suns? Well, kind of. Now there's a star system that's like this and there's a bright star you see in the winter and sometimes the springtime sky called Castor. It's the second brightest twin star in the constellation Gemini, and it has a similar situation to what Vin Diesel saw in Pitch Black.
It consists of at least six stars that circle each other. So these are six suns of different sizes, temperatures, colors, and so, there's still the question, are there any planets around Castor? Hmm. It's unknown as of now. Unlikely because you got all those stars around there, but we can't rule it out because we have found planets around multi-star systems.
Many stars in the sky you see at night, are actually a little more like Castor than like our sun, because more stars up in the sky are really two, three, four or more stars circling each other. Between 60 and 70% of the stars in our section of the Milky Way galaxy are double stars or more. They just look like a single point of light to our naked eye, and that puts our solitary sun, our star, in the center of our solar system in the minority.
Well, what other oddball stars are out there? I think my guest today can help us since he often stares off into the distant horizon like Luke Skywalker on Tattooine.
Dr. Gerard van Belle: Hello there. My name is Dr. Gerard van Belle. I am the Director of Science at the Lowell Observatory in Flagstaff, Arizona. I'm one of the tenured faculty astronomers here, and I work on fundamental stellar properties and astronomical instrumentation.
Dean Regas: Gerard, thanks so much for joining me today. Now, one of your many expertises is in observational astronomical interferometry and designing the equipment to do that. So what kind of unique designs are you most proud of and how do they work?
Dr. Gerard van Belle: So an interferometer is a telescope you build when you don't have enough money to build the telescope you really wanna build. So what you do is you get a bunch of smaller telescopes and you link them together and you can synthesize a single bigger telescope.
And so this has been done for many years on the radio. If you've seen contact with Jodi Foster, she's out there with her headset on in New Mexico and listening to, you know, all these telescopes that are working together,
[Contact Movie Audio]: You can see over there we're building 45 brand new dishes, and that means that when you put them together with all the different radio telescopes all over the world, then we get to hear farther into space than anybody's ever heard before.
Dr. Gerard van Belle: It's easier in the radio because the wavelengths of light are longer, and when you start working in the optical, like I do the, you know, sort of colors of light that your eyes can see, then your mechanical tolerances have to be basically a fraction of the wavelength of lights. But if you can do it, then you can get more zoom out of your telescope than you could get with even the largest single conventional telescopes.
Dean Regas: The way that I understand interferometry is you connect these telescopes over great distances or maybe not so great distances. And whatever their distances apart, you essentially have that size of a telescope. Is that right? Or is that a little too simplified?
Dr. Gerard van Belle: Nope, that's exactly right. And in the case of radio, they're actually able to do it for say, the whole earth.
One key consideration when you're doing optical interferometry is that with radio you can collect the light. And detect the light. And then after the fact, mix it in the optical. You have to collect the light carefully, bring it back together and, and mix it, and then you have to detect it.
And so in the optical, the telescopes are all on a single site, but it's, it's still actually is a big wind because it's like you have a telescope that's a hundred meters in size or a thousand meters in size, and you can see much more detail than the current biggest single telescopes, which only are about 10 meters across.
Dean Regas: And you've worked on both ground-based and space-based instruments.What are the pros and cons of space-based versus earth-based?
Dr. Gerard van Belle: The big win in space is there's no atmosphere, and the big win on the ground is that it's easy to build, easy to test. There actually hasn't really been a significant interferometer ever put in space yet. This is one of the things that I'm pushing on with ground-based things.
You can get them to work, but you're sitting on the surface of the earth, at the bottom of a turbulent, boiling atmosphere, and you basically have to do all of your work in an amount of time where that boiling motion can be frozen out.
If you make a really fast exposure time, you can't necessarily fix it, but you can at least freeze it out and then maybe track it out. You know, it's a lot like if you have a, let's say a coin at the bottom of a swimming pool and you're trying to look at it and it's kind of dancing around. It appears to be dancing around because somebody jumped in the pool and that's what the atmosphere does to you.
And up in space you don't have that. And so you could actually take a very long picture, and that means you can see very, very faint things. If you can get an interferometer up there.
Dean Regas: Some of your research is kind of on oddball stars, you know, like variable stars, low mass stars. But the one that I'm kind of drawn to is your work with Altair and rapidly rotating stars. What did you find with some of these rapid rotators?
Dr. Gerard van Belle: So in interferometry, since we're limited to bright things, one of the things that we do is we basically figure out what is bright enough to see and then we declare it is therefore interesting. And one of these was Altair, which is one of the three stars of the summer triangle. You can walk outside during the summertime and it's one of the, the bright ones of that triangle in the sky. And we, we looked at it closely.
One of the things that I have done over the course of my career is looking at Stars and seeing them as say a disc, it's the same challenge as if, you know you have an orange here in Flagstaff, Arizona, but you managed to put it all the way over in New York City and you can still read, ‘Sunkist’ off that orange.
That's the kind of resolution that we have. We looked at this star and we measured it across one axis, and then had the telescope effectively turn itself around and we measured in a different direction and we got different numbers. So the first thing you're like, oh, well that's crazy and you know, is our instrumentation working correctly?
But it turns out that Altair, unlike our sun, which is a nice round sphere, almost a perfect sphere, in fact, Altair is a lot like a beach ball if you held it in your hands and squished and it kind of popped out at the sides. And the reason for that is Altair, if you compare it to our sun, it's about twice as massive there.
Unlike the sun, which is, you know, in a very stately fashion, rotating every 30 days or so, Altair is spinning every 12 hours. And so it's trying to rip itself apart. It's like you're on a merry-go-round and you're spinning it real fast and you're at the edge of it. It's kind of throw you off and, and so this centrifugal acceleration is at play here, and it's, it's actually significant enough that it's starting to compete with gravity in holding the star together.
And so the middle part of the stars is kind of bulging out. And this was an observation that I did with a team of mine back in 2001, and we were the first ones to ever directly see this.
Dean Regas: Well, it's one thing talking about oddball stars. How about the things that are really, really common, but maybe people don't know very much about it? And I'm talking about low mass stars, you know, mainly like red dwarf stars. They happen to be really quite numerous in our galaxy. And so why are there so many of these low mass stars and what can they help us learn a little bit more about stellar evolution?
Dr. Gerard van Belle: Yeah, there are a lot of these smaller stars. If you look at the range of masses in which we find stars, you'll find things like the sun and you'll find things that are maybe 10 times, even a hundred times greater. Mass than the sun. But then going the other direction, you'll get things that are a quarter, maybe a 10th, maybe even down to 8%, the mass of the sun, and that's kind of where stars bottom out.
But if you look at the pile up of which stars exist, there's a very small number of the big ones. But way on the small end, about 75% of the stars are much, much smaller than the sun. If you were to like a headcount, but if you were to walk outside tonight when it's dark and look for one of these low mass stars, you wouldn't see any because even the very nearest low mass star, they're actually pretty dim.
So the closest one to us is still not bright enough to be seen with our own eyes and to do meaningful work. And so one of the things that I like about being here at the Lowell Observatory, my institution, is that we have our Lowell Discovery Telescope. This is a 4.3 meter telescope that's about an hour outside town.
And I'm able to look at these stars and study them. And there's a lot of interesting things that you can find out on things that. Have been so faint that they haven't been studied a lot, that you've needed a bigger telescope up until now.
Dean Regas: Well, Gerard, this has been a lot of fun chatting about stars, planets, all sorts of things. I really appreciate you taking the time. Thanks so much.
Dr. Gerard van Belle: My pleasure. It's a lot of fun chatting and come to Lowell again. It'd be good to see you out here in Flagstaff again.
Dean Regas: Well, it was great talking with Gerard about the kind of weirder stars out there. Every once in a while there's like a story on the news of like, oh, Betelgeuse has already exploded and it's coming our way. No, no, no.
We have no idea of when it's gonna happen. We have no idea if it happened already. It could have, we don't know. But I hope it does happen in my lifetime. Somebody asked me what is the one thing that I would like to see more than anything in the sky. Now, of course, total solar eclipses definitely, but I've seen three of those.
I've never seen a supernova explosion, and the last really good one was in the year 1604. So, come on Betelgeuse, let's get going on this. I wanna do this. I wanna see this in my lifetime.
The other star I just wanna talk about really briefly is Altair that Gerard was talking about. This is the one that spins really fast and this is a star that you can definitely look for up in the night sky. It's one of the brightest stars up in the summer sky. Altair is really fun, because of how fast it spins. I know Gerard talked about this because of his studies and his research. Take a star, like our sun, it spins about once every month and Altair spins about once every nine or 10 hours, and it's a bigger star than our son.
So check out some of the animations and the videos of some of the work that Gerard did. And it's really kind of cool to see this fast spinning Altair that squishes itself out like an M&M.
Looking Up what Dean Regas is a production of Cincinnati Public Radio. Kevin Reynolds and I created the podcast in 2017. Ella Rowen produces and edits our show and is a rapidly spinning superstar, especially when the deadlines are approaching. Jenell Walton is our Vice President of content, and Ronny Salerno is our digital platforms manager. Our theme song is Possible Light by Ziv Moran. Our social media coordinator is Hannah McFarland, and our cover art is by Nicole Tiffany. I'm Dean Regas. Keep looking up.
