The Real Reason NASA Built This Telescope

The Nancy Grace Roman Space Telescope is on a five-year mission to seek out the invisible cosmic forces that have been shaping our universe from the moment of the Big Bang to the current day. And to accomplish this, NASA is not really just launching one telescope, they're kind of launching a hundred telescopes all at once. But that's what we need to solve one of the biggest mysteries that modern science has ever faced and the answers that Nancy Grace Roman finds will change the way that you see our universe forever. There are two space telescopes that most of us are already familiar with, Hubble and James Webb. Hubble was launched in the year 1990 and if you're like me and grew up in that decade, then you'll know how these images really shaped our view of outer space in those years. Images like the Pillars of Creation somehow managed to be even more beautiful than anything I'd ever watched on Star Trek. And at the same time, Hubble was doing more than just making art for posters and wall calendars. What it found out there would rewrite the book on what we think we know about the nature of our galaxy and the universe around us. Then in 2021, it was James Webb's turn to rewrite history, this time by looking deep into the ancient past and getting us closer to the Big Bang than ever before. The trouble is that in all of the answers that these two machines have provided us over the years, we have only found more questions. It's like the more we learn, the more we realize just how little we actually know. There is a gap in our understanding of the universe and it's only getting bigger with time. That is where the Nancy Grace Roman telescope comes in and its mission will be to fill that gap. Which is a big job for a telescope with a big name that honors a very important person in NASA's origin story and we'll tell you about her in a second. Okay so what makes this telescope so special is the size of the picture it can take. The widest and sharpest image of the night sky ever created. Now I'm a photography nerd so I'm going to use a camera analogy here but I'll assume we've all taken a photo recently. If you open up the camera app on any modern smartphone, you'll probably find at least two lens options, a wide angle and a zoom. The wide angle is great for taking a picture of a forest. You can see all of the trees but when you try and crop in on one of the branches, you find that there aren't really any details there, just mushy pixels. While the zoom lens is great for capturing those details on the branches, it won't let you see the forest. Think of Hubble and James Webb like the zoom lenses. They capture incredible detail in regions of space that are very far away but they can only observe one specific thing at a time. Then think of our ground based observatories like the wide angle lenses. They can see huge areas of the night sky all at once but they can never show us the details. What makes Nancy Grace Roman special is that it can do both jobs at the same time. If we look at some of the most famous images from the Hubble telescope, they are undeniably stunning but the primary camera onboard Hubble uses two image sensors that are each about 8 megapixels for a combined resolution of just over 16 megapixels which for 1990 was incredible but today that's much lower than most cell phone cameras. For James Webb, NASA upgraded the main camera to 8 image sensors each with just over 4 megapixels and a combined resolution of around 34 megapixels. Much better but in many cases still won't match the camera that you have in your pocket. Now this is the wide field instrument on Nancy Grace Roman. It is a collection of 18 image sensors each with over 16 megapixels for a combined resolution of 300 megapixels in one single image. Now you might notice that with so many image sensors there ends up being some gaps in between them. That's why the telescope will use a technique called dithering which is basically just rotating around as it takes photos to fill in the holes. So what we end up with is a final image that is 100 times wider than Hubble's field of view but still has the exact same level of detail. In other words it's like using 100 Hubble telescopes all at once and yet another way to look at it would be that Roman can do in a day what would take Hubble a year. Now what is NASA going to do with all of that information? Well they've got a few big plans for this telescope over the years to come but the most important of all is going to be investigating two of the fundamental yet invisible building blocks of the universe. Dark matter and dark energy. These are two astronomy terms that get thrown around a lot. They sound very similar and are often confused but they are two radically different things. So dark matter is kind of like an invisible glue that holds the universe together. We know that the universe is made of galaxies but those galaxies have a problem. They spin and they spin really fast. Too fast. In fact galaxies spin so fast that even with the billions of stars inside them there should not be enough gravity in there to hold them together. So in the same way that a rocket can fly away from the earth by accelerating to a very high speed the stars in the galaxy should be moving fast enough to just go flying out into space but they don't and the best explanation we can come up with is that there must be some invisible halo of mass that surrounds the galaxies and holds all of the stars in place. Hence dark matter. So we're pretty sure this stuff exists but we don't know what it is or where it came from and that's one mystery that we are going to solve. And then there's dark energy which has an opposite effect on the universe and is somehow even more puzzling. The first thing you need to know is that our universe is expanding. You've probably heard about this but less of us actually know what that means or how it works and that's fine because astronomers who dedicate their lives to studying this stuff don't really know either. See back in the 1920s this guy named Edwin Hubble started noticing that almost all of the galaxies he could see through his telescope were moving away from our galaxy and what Hubble saw was a very shocking thing because at the time Albert Einstein, you know the guy with the hair, he'd already published his theory of relativity and it said that the universe was static meaning that while moons moved around planets and planets moved around stars everything else remained in the same place unchanged over time. But this theory didn't quite make sense with his understanding of gravity which basically says that mass attracts other mass and if space is empty and it's full of these really heavy stars then they should all be getting pulled toward each other by gravity. So Einstein inserted anti-gravity into his theory to maintain the static universe a repulsive force that must exist in the space between and balance out the force of attraction. He named it the cosmological constant. Now what Hubble had just discovered threw a wrench into that perfectly balanced universe because if massive galaxies could actually move away from each other then the force pushing them apart must be even stronger than the gravity holding them together and the way that he tracked the movement of these galaxies would define the way that we look at space for the next hundred years. You see light travels in waves just like sound and in the same way that long waves of sound make the base that comes out of your subwoofer, long waves of light make infrared. These waves are so long that you can't see them with your eyes. They fall below what we call the visible spectrum which sits in between infrared and ultraviolet with UV waves being too short for our eyes to see. But we have tools that can measure all of these different kinds of light and that is what Hubble was using back then. So what we came to understand was that the further away a galaxy is the deeper into the infrared spectrum its light waves would dip and the explanation that we settled on was that the waves must be moving through expanding space that stretches them out more and more as they travel. In simple terms this tells us that the universe cannot be static it is expanding and because the light from the furthest galaxies experiences the largest amount of stretch it means that the rate of expansion is not constant it's actually accelerating over time. This is how we end up with our current model for the Big Bang. If everything in the universe is moving outward right now then by rewinding that back to the beginning we'd see the universe contract back down to one single point of origin. Makes sense right? Except if it all started with a Big Bang and everything expanded out through empty space then the seed of expansion should remain constant from that bang but it doesn't. So the best explanation we can come up with is that there must be some invisible force in the empty space that is actively creating more empty space. We call that dark energy and the crazy thing about this one is that if space keeps expanding at a faster and faster pace then eventually everything will become so spread out that no new galaxies can form and then no new stars can form and then inevitably the universe becomes a cold dark wasteland. That's a pretty bleak future but luckily it's also just a theory and one that the Nancy Grace Roman telescope might be able to prove wrong by providing more answers about the true nature of dark energy. Okay before we get into any more technical details let's talk about who Nancy Grace Roman was and how she got a space telescope named after herself. Nancy first became an astronomer in the 1940s and completed her PhD at the University of Chicago. Then she would go on to publish one of the most important and most cited papers in all of modern 20th century astronomy. It was basically a guide on how to locate different types of stars within the Milky Way galaxy, identify the different characteristics of old stars and new stars, and helped us start figuring out how our galaxy came to be. This was impressive enough to land her a job at NASA right when the space agency was first created in 1959 and by 1960 Nancy Grace Roman became NASA's first ever chief of astronomy giving her the authority to choose which scientific projects the agency would pursue and making her responsible for organizing the human resources and funding necessary to make those projects successful with one of the final major things she worked on being the development of the first ever space telescope which is why she's often remembered as the mother of Hubble. So after her passing in 2018 at the age of 93 it only seemed fitting that NASA's true successor to the Hubble telescope would be named in her honor and this is where we can get into how the Nancy Grace Roman telescope works because it is pretty much identical to Hubble in terms of size and function just with a much higher resolution. Now this is very different from the James Webb Space Telescope which most people probably think of as an upgraded Hubble but it's actually a very different instrument that is trying to achieve a very different goal. So both Hubble and Roman see in the same visible light spectrum as the human eye plus they get down into the near infrared zone so remember that the further light travels the more it gets stretched down into infrared. This means that these two instruments can see things in space that are close to our galaxy and kind of into the middle distance as well. On the other hand James Webb sees from near infrared light to medium infrared meaning that it's a little bit blind to anything that's close by. That's why Webb's images of nearby planets like Jupiter look all weird and ghostly it's just the infrared light but this does mean Webb can see far into the distant universe. So a Hubble class telescope and a Webb class telescope are complementary instruments meaning you actually get the best most complete picture when you combine the two together. Now as Hubble reaches the end of its useful lifespan Roman and Webb are going to begin working hand in hand with Roman's wide field of view being able to spot new and interesting regions of space and then Webb zooming in to look deep through the visible surface layer and into the dark. On its own Roman will conduct the search for dark matter and dark energy by hunting for two distinct features in the visible universe bubbles and supernovas. Bubbles in space help us to locate dark matter that's because a large enough concentration of gravity has the power to bend light just like a magnifying glass so you'll actually see the effect of this cosmic lens in the visible light and it ends up creating a kind of distortion like a bubble. Wherever we see one of those distortions in a region of space that looks otherwise empty we know that a cluster of dark matter is hiding. Now supernovas help us find dark energy by providing a reliable measure of distance because we know that the brightness of an exploding star is pretty consistent we call that a standard candle and if you think about the type of candle that you light at home you know that the closer the flame is the brighter the light will appear and the further away you get the dimmer the light will appear. The same idea works in space with these supernovas so the differences that we see in their brightness give us a way to measure how far away they are and when we combine that visual observation with an instrument called a spectrograph which measures the wavelengths of light we can not only get the distance of the supernova we can also tell how fast the galaxy around it is moving away from our location. That reveals how much dark energy is located in the space between. These bubbles and supernovas are not easy to spot. With a telescope like Hubble you pretty much have to be looking in the right place at the right time but when Roman can see 100 times more space than Hubble we are going to find 100 times more anomalies. So by using these tricks we are able to transform a two-dimensional view of space into a three-dimensional image that reveals the hidden invisible forces that exist between the visible galaxies and then once we have this gigantic map that shows us where dark energy and dark matter are located in the universe we can use the deeper view of James Webb to follow that map back to where all of this stuff came from in the first place and hopefully that starts to provide us with an explanation into what these invisible forces actually are. Fortunately we won't have to wait very long for this journey to start. After launching on a Falcon Heavy rocket in late summer the Roman telescope will travel out past the moon and arrive at the L2 Lagrange point. This is like a gravitational parking spot and it's the same one where we've already parked the James Webb telescope. Now unlike James Webb Roman won't have to go through a complex unfolding and calibration process so we expect to be seeing the first images arrive by early December. Once Roman begins its survey the telescope will be downloading about 1.4 terabytes of information per day back to earth all of which will be publicly available and it's almost certain that Roman will capture so much data that people will spend decades sorting through it all and making new discoveries well into the future.