The Roman Space Telescope will reveal the universe in a way the JWST and Hubble cannot
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Even if you aren’t the kind of person who often looks up the latest space images, it’s hard to navigate life (especially on the internet) without running into a few. Try choosing a new iPhone background and you’ll have your pick of sharp, gray moon portraits. Watch an old “Star Trek” episode and you may not realize how many of those translucent nebulas outside the spaceship’s windows were based on real, hard data.
When it comes to space, we’re spoiled. Mind-bending objects light-years away from us have managed to become integrated into our everyday lives — and though we’re still a ways away from understanding the true nature of the universe, we’re also the closest we’ve ever been. It’s in large part thanks to how impeccable our fleet of space telescopes is. In seconds, you can find a Hubble Space Telescope Deep Field with luminescent galaxies warped along the curvature of spacetime and James Webb Space Telescope images of strange hazy red objects from just after the dawn of time.
Moreover, what’s tremendously exciting is this fleet is constantly growing. Indeed, very soon, a new space telescope will launch from NASA’s Kennedy Space Center in Florida. It’s called the Nancy Grace Roman Space Telescope, and it should be able to unlock a new level in the astronomy layer of our lives. It will show us new types of images, reveal new types of data and lead us in directions we may not yet know are possible.
What is Roman?
To put it succinctly, the Nancy Grace Roman Space Telescope is an approximately 42-foot-long (12.7-meter-long), cylindrical metal observatory scheduled to lift off from our planet on Aug. 30 aboard a SpaceX Falcon Heavy rocket.
Across a five-year-long mission (a 10-year-long one if everything goes well), Roman is meant to use two powerful instruments — the Wide-Field Instrument (WFI) and Coronagraph Instrument — to image huge swaths of the cosmos and tackle some crucial questions. It will help scientists probe the mysteries of dark matter and dark energy, directly image exoplanets near and far, witness an extensive amount of stars exploding in colossal supernovas and more.
But whether or not it’s a fair thought, it’s hard not to want to compare the specifications of this space telescope to some of the others that have brought the cosmos down into our daily lives. This is particularly true for two of the major players right now: the James Webb Space Telescope and the Hubble Space Telescope.
What can Roman do that these two cannot?
Roman vs. Hubble
To start, one of the biggest benefits of Roman over Hubble is its processing power.
By numbers, that means Hubble has managed to gather about 400 terabytes of data over its approximately 35 years of service so far. Roman is expected to be able to create 500 terabytes of data every single year.
“Its surveying capabilities are over 1,000 times faster than Hubble, and can chart 200 times more sky in a single image,” NASA administrator Jared Isaacman said during a press conference about Roman in April. “What would take Hubble 2,000 years to process, Roman can do in a year — the images it captures will be so large there is not a screen in existence large enough to show them.”
Roman’s primary mirror is about 7.9 feet (2.4 meters) wide, which is actually the same as Hubble’s. Primary mirrors are arguably the most important aspect of a space telescope, because it’s how an observatory manages to gather light coming from the universe. Bigger mirrors can collect more light, which allows them to see dimmer or more distant objects. Interestingly, Roman’s primary mirror is also about 80% lighter than Hubble’s. Roman has a secondary mirror as well; it’s just under 2 feet (0.5 meters) wide. Hubble’s secondary mirror is very similar at exactly 12.2 inches (0.3 m) in width.
Yet even though Roman’s mirrors are so comparable to Hubble’s, because of Roman’s processing power as well as the capabilities of its WFI, it will be able to image a far wider stretch of sky than Hubble can.
Though Roman does have some visible light capabilities like Hubble, WFI specializes in infrared light — actually the kind of light the JWST works with, but we’ll get to that telescope comparison shortly — so we should compare it to Hubble’s infrared instrument. The WFI’s field of view is about 100 times greater than the Hubble infrared instrument’s field of view.
According to NASA, this view will allow Roman to measure light emanating from a billion galaxies and billions more cosmic phenomena over its years of service.
“Both observatories will perform spectroscopy,” NASA explains, “which involves splitting light into individual colors to study patterns that reveal detailed information. But Roman’s spectral studies will have lower resolution over a large area, while Hubble’s has higher resolution over a small area.”
This concept really sums up the difference between the two telescopes, and in fact foreshadows what we’ll soon discuss about the JWST.
Roman vs. the JWST
The main similarity between the Roman Space Telescope and the JWST is those infrared light goggles.
Infrared light, unlike visible light, is invisible to human eyes. You can think of it more like a heat signature. Firefighters, for instance, use infrared trackers on burning buildings from the outside to see where the source of the fire might lie within. And when it comes to astronomy, infrared light is priceless — that’s why the JWST’s strong infrared capabilities give it an advantage over Hubble.
Infrared light’s role in astronomy observations has to do with the way light moves throughout the universe. As light from a distant region of space moves toward us — through a continuously expanding universe, no less — those light wavelengths stretch out from tight, bluer ones into long, redder ones. Eventually, the wavelengths stretch out into the infrared region of the electromagnetic spectrum, which is the part of the spectrum we cannot see with our own eyes. Plus, any objects in our line of sight that are hidden behind dense clouds of interstellar dust or gas can only be seen via their infrared emissions.
What this means is that very, very distant objects as well as concealed objects in space are pretty much invisible to us, hiding in the infrared part of the spectrum. We therefore need infrared decoders, like the JWST’s suite of tools or Hubble’s infrared instrument, to reveal them.
The JWST has already made absolute strides in this regard, revealing to us peculiar objects from the early years of the universe, consistently breaking its own record while finding the most distant galaxies we’ve ever seen and revamping Hubble portraits like the spectacular Pillars of Creation with its infrared filter. It’s even reintroduced us to our own solar system with crisp views of Neptune‘s frail, oft-forgotten rings and Saturn‘s big, bright ones.
When it comes to mirrors, the JWST’s iconic golden primary mirror made of 18 hexagonal segments is a beautiful 21 feet and 4 inches (6.5 meters) across, which is much larger than Roman’s. This means the JWST can collect tons more light than Roman can, which makes a lot of sense because it was built to see as deep into the ancient universe as possible.
But where the JWST lacks is, you guessed it, its field of view. This is on purpose. The whole point of JWST is to pierce into the universe with a highly narrow view in order to get great resolution on whatever it’s looking at. Roman definitely won’t be getting that same resolution, as its images will be shallower than the JWST’s, but its WFI will see a region 50 times wider than what the JWST can see.
To be clear, there are indeed other survey telescopes that are able to image huge amounts of the sky at once, but Roman’s version of doing this is expected to be with higher clarity. For example, the ground-based Rubin Observatory is revolutionary for the vast amounts of data it’s able to collect while scanning a new section of the sky every 40 seconds. However, Rubin is on the ground. A space telescope sits above Earth’s atmosphere, and therefore has less atmospheric interference to sift through. This makes the observations way better.
Okay, you’ve probably figured out the moral of the story at this point: Roman’s reach is shallower than Hubble’s and the JWST’s, but extremely wide. So, what’s the benefit of this enormity?
The promise of Roman
Imaging huge amounts of the universe in one go is of foremost importance because things in the universe happen simultaneously. A supernova on one end might be worth checking out, but a fleeting fast radio burst buzzing on the other end of the cosmos could be just as vital to study. Yet, with a narrow field of view, you’d have to select which target to zoom in on. And if you aren’t sure which targets are even options, while perusing an ancient black hole with immense resolution you will most definitely miss an even older one that lurks 50 frames or so away.
With Roman, scientists won’t have to be as selective about which parts of the sky they scan. Roman is designed to be able to capture the supernovas, fast radio bursts, black hole emissions and warped galaxy candidates all at once. For example, NASA explains how Roman will be able to spot colliding neutron stars — stellar corpses so dense a tablespoon of one is equal to the weight of Mount Everest — with its infrared view. The JWST would likely never even come across such an event due to its tunnel vision.
Of course, Roman won’t be able to image these objects with as much depth as the JWST or Hubble — or several other telescopes for that matter, like maybe SPHEREx or Euclid — but it will be able to notice that these objects exist.
The next step would be to have one of those other telescopes follow up on the targets. You can think of Roman as creating the Google Maps of hotspot locations in the universe that the JWST, Hubble or another telescope may want to examine someday.
Big field of view means big science
Furthermore, capturing information from billions of objects in such a short period of time will enable specific kinds of research, such as the hunt for the truth about dark matter and dark energy. Despite collectively making up about 95% of the universe’s contents, dark matter and dark energy aren’t visible to us. However, we know dark energy exists because it appears to be applying a force that accelerates the expansion of our universe and we know dark matter exists because it seems to be the glue around galaxies that prevents them from falling apart like horses on a merry-go-round spinning too fast.
What this means is imaging tons of galaxies at once could allow scientists to have a better picture of how those interactions between the dark universe and our regular universe play out. Roman will also be able to create time-lapse “movies” of the universe in three dimensions and offer scientists the chance to see how other observations fit into that picture.
It would also be remiss not to mention what Roman’s other instrument can do: the coronagraph. The telescope’s coronagraph is actually one-of-a-kind. You can think of it like a special artificial eclipse that brings objects into view that would otherwise be obscured by bright starlight. No other space observatory in service right now has the ability to directly image exoplanets like Roman will be able to using that coronagraph. It would take an entire other article to explain the awesome complexities of this instrument — an article that you can definitely expect soon — but to go through the basics, this tool will block out the glare of distant stars and then measure the polarization of light around them in order to help scientists tease out exoplanets orbiting those stars.
According to NASA, Roman’s coronagraph will be able to detect planets 100 million times fainter than their stars. That capability is about 100 to 1,000 times better than existing space-based coronagraphs. This will give scientists the opportunity to study planets beyond our solar system that are dimmer, colder, farther and more elusive than what we’re currently able to see.
With all this in mind, there is an important concept to remember.
When the JWST first entered service in the year 2022, everyone (including me) started comparing it to Hubble and thinking of it as Hubble’s upgrade. It’s hard not to, especially when the images rolling out of a shiny new telescope are so utterly gorgeous. But “upgrade” couldn’t be farther from reality. The JWST is just different. Impressive, sure, but different. The goal is for all of these telescopes to work together, each one giving us a new sheet of the universe to explore. Stack up all the sheets, and you’ll get the full picture.
Roman will simply be offering us one breathtaking new sheet.
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