Millions of galaxies appear in new simulated images from NASA’s Nancy Grace Romanian Space Telescope






This image of the Roman Deep Field, which contains hundreds of thousands of galaxies, represents only 1.3 percent of the synthetic survey, which itself is just one percent of the planned Roman survey. The galaxies are color-coded – redder galaxies are farther away and whiter galaxies are closer. The simulation demonstrates Roman’s ability to perform large, deep surveys and to study the universe statistically in ways not possible with current telescopes. Credit: M. Troxel and Caltech-IPAC/R. Hurt

Scientists have created a huge synthetic survey that shows what we can expect from future observations by the Romanian Nancy Grace Space Telescope. Although it’s only a fraction of the real future survey, this simulated version contains an astonishing number of galaxies – 33 million of them, along with 200,000 stars foreground in our home galaxy.

The simulation will help scientists plan the best observational strategies, test different methods for mining the massive amounts of mission data, and explore what we can learn from tandem observations with other telescopes.

“The amount of data that Roman will return is unprecedented for a space telescope,” said Michael Troxell, associate professor of physics at Duke University in Durham, North Carolina. “Our simulation is a testing ground that we can use to make sure we’re getting the most out of the mission’s feedback.”

The team drew data from a fictitious universe originally developed to support science planning using the Vera C. Rubin Observatory, which is located in Chile and is scheduled to begin full operations in 2024. Because Roman and Rubin’s simulations use the same source, astronomers can compare them and see what They can expect to learn it from pairing telescope observations once they actively survey the universe.

A paper describing the results, led by Troxell, has been accepted for publication in Monthly Notices of the Royal Astronomical Society.


This video begins by showing the most distant galaxies in the simulated deep field image in red. As you zoom out, layers of nearby galaxies (yellow and white) are added to the frame. By studying different cosmic eras, Roman will be able to trace the history of the expansion of the universe, study how galaxies have evolved over time, and much more. Credit: Caltech-IPAC/R. Hurt and M. Troxel

cosmic construction

Roman’s wide-latitude region survey will consist of both imaging — the focus of the new simulation — and spectroscopy across the same vast swath of the universe. Spectroscopy involves measuring the intensity of light from cosmic bodies of various wavelengths, while Roman imaging will reveal precise locations and shapes of hundreds of millions of fainter galaxies that will be used to map dark matter. Although this mysterious substance is not visible, astronomers can infer its existence by observing its effects on ordinary matter.

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Anything with mass warps the fabric of space-time. The larger the mass, the greater the torsion. This creates an effect called gravitational lensing, which occurs when light from a distant source is distorted as it passes through intervening objects. When these lenticular objects are massive galaxies or galaxy clusters, the background sources can be smeared or appear as multiple images.

Less massive objects can create more subtle effects called weak lensing. Roman would be sensitive enough to use the weak lensing to see how clumps of dark matter distort the appearance of distant galaxies. By observing these lensing effects, scientists will be able to fill in more gaps in our understanding of dark matter.






This graphic compares the relative sizes of the synthetic image (inset, outlined in orange), the entire simulated region (top center box in green), and the size of the entire future survey that astronomers will perform (large square in lower left left outlined in blue ). The background, from the Digital Sky Survey, shows how much of the sky each area covers. The synthetic image covers as much of the sky as the full moon, and a future Roman survey will cover a much larger area than the Big Dipper. Whereas the Hubble Space Telescope or the James Webb Space Telescope would take about a millennium to image an area the size of a future survey, Roman would do so in just over seven months. Credit: NASA’s Goddard Space Flight Center and M. Troxel

said Chris Hirata, a professor of physics at Ohio State University in Columbus, and a fellow author of the paper.

“But predictions are statistical in nature, so we test them by observing vast regions of the universe. The Roman sphere, with its wide field of view, will be improved to scan the sky efficiently, complementing observatories such as the James Webb Space Telescope designed for deeper investigation of individual objects.”

Earth and space

The Roman Synthetic Survey covers 20 square degrees of the sky, which is roughly equivalent to 95 full moons. The actual survey will be 100 times larger, revealing more than a billion galaxies. Rubin will scan a larger area — 18,000 square degrees, roughly half the entire sky — but with a lower resolution because it will have to peer through Earth’s turbulent atmosphere.

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This animation shows the kind of science astronomers will be able to do with Roman deep field observations in the future. The gravity of the overlapping clusters of galaxies and dark matter can reflect light from distant objects, distorting their appearance as shown in the animation. By studying distorted light, astronomers can study the elusive dark matter, which can only be measured indirectly through gravitational effects on visible matter. As a bonus, this lens also makes it easier to see distant galaxies whose light is magnified. Credit: Caltech-IPAC/R. Hurt

The coupling of the Roman and Rubin simulations provides the first opportunity for scientists to attempt to detect the same objects in both sets of images. This is important because terrestrial observations are not always sharp enough to distinguish multiple nearby sources as separate objects. Sometimes they fade together, affecting poor lens measurements. Now, scholars can determine the difficulties and benefits of “unpacking” such objects into Robin’s images by comparing them to Roman objects.

With Roman’s massive cosmogonic view, astronomers will be able to accomplish much more than the survey’s primary goals, which are to study the structure and evolution of the universe, map dark matter, and distinguish between leading theories that attempt to explain why the universe is expanding. The universe is accelerating. Scientists can comb through the new simulated Romanian data to get a taste of the additional science that would come from seeing so much of the universe in such exquisite detail.

“With Roman’s enormous field of view, we anticipate many different scientific opportunities, but we will also have to learn to expect the unexpected,” said Julie McEnery, lead project scientist for the Roman mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. . “The mission will help answer critical questions in cosmology while revealing entirely new mysteries for us to solve.”

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