Short Wave - NASA's newest telescope has a top secret past

Episode Date: August 28, 2026

The new Nancy Grace Roman space telescope is slated to launch this weekend. It was originally built for the National Reconnaissance Office as a spy satellite, but was never launched. Instead, NRO gave it to NASA about 15 years ago. After some major modifications, it’s set to begin its five-year mission peering at new supernovas, distant galaxies and planets orbiting stars outside our solar system. It should help scientists get a better understanding of the mysterious force known as dark energy – which will tell us about the fate of the universe.If you liked this episode, check out Regina’s reporting demystifying the mysterious red dots spotted by the James Webb Space Telescope.Interested in more space news? Email us your question at [e-mail] public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, shortwaiver is Regina Barbara here. Get ready because we're about to get an entirely new window into the universe. The Nancy Grace Roman Space Telescope called Roman by its friends is scheduled to launch at the end of August. So he called up an old friend of Shortwave, former NPR science correspondent Joe Palka, to talk about it. Hey, Joe. Hey, Gina. So I hear that astronomers are stoked about this thing.

I mean, I am. Yeah. is a pretty good way to put it. If it delivers on what we think, it will be the best thing ever. Yeah, that's a version of Stoked. That's Daniel Skolnick of Duke University, one of the scientists who will be using Roman data to unlock the mysteries of the universe.

Okay, so Joe, what have you been learning about the Roman telescope? Oh, lots of stuff. To start off, it was named after a woman you maybe never heard of. I hadn't. She was NASA's chief astroner back in the 60s and 70s, Nancy Grace Roman, and she gets credit for getting the Hubble Space Telescope from an idea to a reality. But one of the most unusual things I learned is that this Roman telescope wasn't originally built to look at the heavens. It was designed to be a spy satellite.

I am looking forward to hearing all about how that happened. Today on the show, a preview of the Roman Telescope mission and its curious origins. You're listening to Shortwave, the science podcast from NPR. So, Joe, I'm really intrigued by this spy satellite lore. How does a spy satellite become a space-based, like, telescope observatory? Yeah, well, some of the details are murky because it involves the National Reconnaissance Office. Right. And that's an agency of the government that manages surveillance assets.

And the office was once so secretive that government didn't even admit it existed. Wow. So the story goes, every 10 years, astronomers put together. a list of their top priorities for the coming decade. And in the 2010 Decadal Survey, astronomers agreed they wanted a telescope that could look for more examples of type 1A supernovas. These are a particular type of exploding stars. Yeah. So astronomers love these type 1A supernovas, these exploding stars, because they all seem to have the same brightness. So if you like catch one and it appears and you measure its brightness, you can tell how far away it is. They're called standard candles. It's kind of like if you had a candle next to you and the exact same candle down the street, the candle down the street is going to be dimmer. But how much dimmer is actually just due to that distance. Yeah. I called it a cosmological yardstick.

Yeah. It's a great tool. But anyway, that was what the 2011 Nobel Prize went for. And it was for using these standard candles to discover dark energy, a force that explains why the universe is expanding and accelerating when gravity suggests it should be slowing down or even contracting. Yeah. Anyway, going back to Dan, that astronomer or cosmologist we heard from earlier, he said one day, 15 years ago, when NASA was in the midst of planning to build this telescope to look for more of these supernovas, the agency got a call. The National Reconstance Office reached out to NASA saying we have this amazing satellite sitting in a hangar that we're not using. And what do you guys think about? Instead of pointing downwards, we point upwards and you guys use it. I love this so much. So like instead of spying on Earth, we're using it to spy on alien worlds. Right. And so it never actually got into space and it was sitting in a garage essentially in Rochester, New York until NASA got hold of it.

Nice. Well, how much did NASA have to modify it? Well, there were a lot of modifications, but some of the key bits like the main mirror for collecting light, that was already built. Right. Okay. So it has a mirror. What else does this telescope have going on for it? Like what instruments does it use to collect this data? Well, there's two main instruments. One is called a coronagraph, and Roman's coronagraph essentially cancels out the light from a star and allows a camera to see a much fainter object, like a planet orbiting nearby. It's a technology that's never been flown in space before, so it'll be interesting to see if it works and how well. I remember using Hubble Space Telescope images in grad school, and I had to manually do this, just cancel out, you know, light from something

really bright to see the dimmer things in the image. Yeah. And the other main instrument, that'll be used quite a lot as the wide field instrument, which is basically a 300 megapixel infrared camera for taking pictures of these huge numbers of stars that the telescope will see with each image. Right. Okay. So to that end, if the main mirror is about the size of the Hubble's main mirror, what can Roman do that Hubble just can't? I mean, other than being like newer. Yeah, no, newer is always good. But it has a much wider field of view, so it can see a much broader swath of the sky. And Julie McKenery says there's another key difference. Julie is Roman's project scientist. And at a recent news conference, she said that one of the observations the telescope will make is a survey of all the stars in the Milky Way galaxy.

Roman has broadly the same sensitivity and sharpness of vision as Hubble, but we survey the sky much faster. So that one month of observations to survey our Milky Way galaxy would take about a century with Hubble. This is so amazing. Surveys are so important to astronomy. This is great. Without a survey telescope, you just couldn't do that. And even the newer James Webb Space Telescope,

it has a bigger mirror, but it has a much smaller field of view, so it only looks at a small patch of sky at a time. Yeah. So getting the same amount of data from either of these telescopes would take longer than the lifespans of them being in space. Yeah.

This is a telescope that was built to do surveys. Right. So it takes broad pictures of this. sky instead of focusing on one or two objects. And Julie says that meant rethinking how the telescope would be used. Our model isn't the traditional astronomers write proposals and get time on the telescope and go off and do a thing. I mean, we do that as well, but that's not the primary way to use Roman. So what we did over the last few years was to work with the scientific community all over the world and ask them for their ideas on how we should use Roman. And what they

came up with is several surveys that will collect data over months or years that scientists will all get equal access to. And they can just like download it from their website. This was kind of similar to Hubble. There was a lot of archival data and people got degrees from that data. Yeah, anybody can get it. And when I say anybody, Julie McHenry says, yeah, really anybody. You can be a teacher in a high school in Kentucky and your students have the opportunity to see Roman data, new Roman data, new Roman discoveries at the same time as a professor in Princeton. That's so cool. Some of these surveys are what are called time domain surveys, which means they look at the

same patch of sky over and over. And if you're wanting to find type 1A supernovas, you have to keep checking the same patch of sky because you don't know when an exploding star is going to appear. Yeah, so you look at these images, you know, separated by hours. or weeks, and you look for things that aren't in the earlier images, like if something popped up. Yeah, exactly. They say things that go bump in the night. I like that. Yeah. So do you have an idea of how many type 1A supernova, these special exploding stars, how many they might find? Right. I asked Dan that researcher from Duke we heard from earlier,

and he said he expects it'll be in the thousands. Yeah. And he says finding them will help scientists better understand how fast the universe is expanding and could confirm our discredit the current model of the entire universe that scientists currently reference. In the last few years, there have been measurements saying that model might be wrong. And that's something that Roman will absolutely nail. Roman will just hit really hard. I cannot wait. Okay.

So in addition to finding more of these supernovae, like what else do astronomers hope to learn from the surveys that Roman will be doing? Well, one of the surveys is this line to look for galaxies and galaxy clusters. Oh, that's my bread and butter. The distribution of these should reveal important information about the nature of dark matter and how it interacts with these giant objects. But they're also hunting for exoplanets. Exoplanets, the planets that orbit, distant stars, you know, not planets in our solar system, but orbiting some other star that is in our sun. Right. And there are several techniques for doing this. The most common one that people may have

heard of is using something called transits where light dims when a planet passes in front of the star. But that only works if the planet's orbit causes it to pass in front of the star as we see it from Earth. Yeah, it's super important, like the angle you're looking at this planet, because it's eclipsing the star, basically. Right. But Roman is going to use a different technique called microlensing, which involves measuring the deflection of light from a star when a closer star with orbiting planets passes in front of it.

The technique was famously described by Albert Einstein in a 9th. 1936 paper, although he thought this would never be a useful thing because it would be too hard to measure. But Scott Gowdy helped prove him wrong. Scott is an astronomer who co-developed this thing called gravitational microlensing technique. Since Roman will be looking at hundreds of millions of stars, the expectation is they'll see tens of thousands of these microlensing events. We're looking for planets that are just completely undetectable by any other method, including planets that are, you know, at the center of our galaxy and planets that are very analogous to our own solar system planets like Jupiter, Saturn, Uranus, and Neptune.

I think it's fascinating that, like, the curvature of space and it bending can help us find planets. Like, this is so sci-fi to me, you know, like microlensine was something I learned in grad school, not related to planets. So this is so cool. Okay. Yeah. And it's pretty interesting that you can use the same telescope.

to do such different kinds of surveys, one looking for exoplanets and the other looking for supernovas. And basically, they have the same observational needs. But Scott told me there are some slight differences in the way the surveys are conducting, depending on what you're looking for, maybe the frequency with which you survey the same patch of sky. And that has led to what he describes as some friendly tension between astronomers who are interested in exoplanets and those who are interested in finding supernovae. Oh, yeah. I can see that.

Then it gets into these very existential questions like which science is more interesting, exoplanets or measuring the equation of state of the universe, which of course, there's no way to actually objectively answer that question. I mean, I kind of agree with them. It's really hard. I do not want to be in one of those camps. I'm not. No. Well, I'm definitely not. So don't point at me.

Okay. So neither of us are going to join that, like, debate. But, Joe, is there a particular area of astronomy that you're excited about? that's going to come out of this telescope. What I like are the things that we don't know what to get excited about. No one knew what the Hubble telescope would find when it started looking at an empty patch of sky for 100 hours. And suddenly the deep field surveys revealed that the sky was anything but empty. It was filled with galaxies.

And now the James Webb Space Telescope has found what they're calling little red dots. And no one is sure what the heck those are. There was a paper earlier this month in nature saying these might actually be an entirely new. class of celestial objects. Yeah, the little red dots have been like everywhere in astronomy. Oh, I just did a story in a past episode about these, these little red dots and how they could be this like new maybe black hole star. We'll link to that in our show notes in case anyone else wants to hear about it.

Well, I'm just saying that I want to call them Joe dots. So there's a memorable name. Sounds like a donut hole and like a cup of Joe. It's just breakfast. Joe Dots, come on. So how soon will we see results from these surveys Roman is doing? Like these new celestial objects, we don't even know we're going to find. Right.

Well, it's going to take Roman about 100 days after it leaves Earth to cruise to this L2 Lagrange point, which is a spot where it can go into a stable orbit. It's about a million miles from Earth. And then, of course, they start the surveys, and these take a while. So there may be a while before we get the full results from Roman, but the first dribs should trickle in probably three or four months after launch. Joe, thank you so much for bringing us the sneak peek of the Roman Telescope, and we're excited to have you back when there's data.

Yeah, exactly. Hope so. This episode was produced by Burley McCoy and edited by a showrunner Rebecca Ramirez. It was fact-checked by Tyler Jones, and the audio engineer was Jimmy Keely. I'm Regina Barber. Thank you for listening to Sherwin. from NPR.