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Scientific American
a day ago
- Science
- Scientific American
Gaia's Long Goodbye
This observatory has probably been the most transformative astronomy project of the 21st century, but there's a good chance you've never heard of it. Just last week, for instance, the Hayden Planetarium at the American Museum of Natural History (AMNH) in New York City debuted a new 'space show' called Encounters in the Milky Way —and this often overlooked spacecraft is its scientific superstar. But you're more likely to know about actor Pedro Pascal's narration in the show than you are to be familiar with the single space mission that serves as the presentation's backbone. The observatory is called Gaia. And, like so many good things, you wouldn't really miss it until it's gone—and now it is. Launched in 2013 by the European Space Agency (ESA), it ceased operations this past March, when it used what little fuel it had left to steer into a graveyard orbit around the sun. From its station in a quiescent region of deep space more than 1.6 million kilometers from Earth, Gaia's mission was, in essence, quite simple: it was designed to give us a better sense of where we are—a celestial 'reference frame' on overlapping interplanetary, interstellar and intergalactic scales. To do that, it used twin sky-sweeping telescopes and three instruments, including a billion-pixel camera, to painstakingly measure the distances, positions, motions, and more of about two billion celestial objects, most of them stars in our own galaxy. It made some three trillion observations in all, producing (among many other things) the largest, most precise three-dimensional map of the Milky Way ever made. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. 'Gaia was our best galactic cartographer, and I sometimes say that Encounters in the Milky Way is my love letter to it,' says Jackie Faherty, a senior research scientist at the AMNH, who curated the new space show and regularly works with Gaia data. 'It turns out you can learn a lot by determining where and how far off the stars are from you—and especially by how they are moving.... Gaia's creation of this map is something we all should celebrate because it's just as iconic and useful as the maps of Earth we all see in school or pull up on Google. Looking at it, you can find and explore all sorts of different things you want to know.' From Gaia's map, more than 13,000 peer-reviewed studies have already emerged, and many have concerned the fundamental structure and deep history of the Milky Way. Thanks to Gaia, scientists now can better gauge the amount of dark matter within our galaxy and have been able to track the Milky Way's growth and evolution across eons via relic streams of stars strewn from ancient mergers with other, smaller galaxies. 'Stars retain memories of their origins in their ages, motions and chemical compositions—all of which Gaia measured,' says Amina Helmi, an astronomer at the Kapteyn Astronomical Institute in the Netherlands. She and her colleagues used the mission's data to discover evidence of a major galactic merger that, some 10 billion years ago, shaped our home galaxy into the Milky Way we know today. 'With all that information, it was like a veil being lifted…. We could suddenly perform what's sometimes called 'galactic archaeology,' reconstructing the Milky Way's history to see when and how this merger happened with another, smaller galaxy that was about a third to a quarter of our galaxy's mass.... Gaia allows us to look billions of years into the Milky Way's history—before our solar system even formed—to see what actually happened back then, which is absolutely amazing.' Tracing perturbations from one more recent and ongoing merger, astronomers have even managed to reveal an apparent warp in the Milky Way's disk, offering a new twist—literally—on the classic image of our cosmic home. At smaller scales, the spacecraft has refined the orbits of more than 150,000 asteroids, surveilling hundreds of them to see if they have their own moons. It has spied hints of thousands of worlds and even a few black holes orbiting other stars. At larger scales, it has helped estimate the expansion rate of the universe, and it has also teased out the subtle tugging of the Milky Way's heart upon the solar system across tens of thousands of light-years. Gaia's sprawling cosmic reckoning is now a cornerstone for most state-of-the-art Earth- and space-based telescopes, which rely on the mission's target-dense celestial map to orient and calibrate their own observations and operations. Whether it's NASA's James Webb Space Telescope, ESA's Euclid mission, the ground-based, U.S.-built Vera C. Rubin Observatory or Europe's under-construction Extremely Large Telescope, practically all of the world's most exciting starlight-gathering telescopes will, in some sense, be guided by Gaia. And stunningly, the best is yet to come. More than two thirds of the mission's treasure trove of data is still under wraps. It is being prepared in a time-consuming process for two major upcoming milestones: about half of Gaia's total data are targeted for release next year, and the mission's full data are set to arrive no earlier than 2030. But because it didn't beam back images ready-made for lush wall posters and desktop backgrounds, Gaia was destined from the start to be 'criminally under-recognized outside astronomy,' says Mark McCaughrean, an astronomer and former senior adviser to ESA. 'And because Gaia provided utterly essential, if mundane, information such as precise stellar distances, it's been doomed with this curse of simultaneous ubiquity and obscurity as many people use its data but take it for granted as just 'coming from a catalog.'' Anthony Brown, an astronomer at Leiden University in the Netherlands, who leads the mission's data processing and analysis group, puts it most succinctly: 'For astronomers, Gaia has become almost like the air you breathe,' he says. At the heart of Gaia's mapmaking is a technique called astrometry, the measurement of celestial positions and motions in the plane of the sky. Paired with a phenomenon called parallax—the apparent shift of an object's position when viewed from two vantage points—astronomers can use Gaia for determining distances, too. You can see the parallax effect with your own two eyes: hold your thumb out at arm's length and watch as it appears to jump around as you blink one eye and then the other. The closer the object is, the bigger its displacement will be. And the bigger your baseline is between two vantage points, the smaller the displacement will be that you can discern. Your eyes have a baseline of about six centimeters; Gaia's was 300 million kilometers, set by the opposite sides of Earth's orbit around the sun. A Gaia predecessor, ESA's Hipparcos mission, used that same gigantic baseline to survey the sky from 1989 until it ran out of fuel in 1993. But the technology of the time limited Hipparcos's astrometric reckoning to a precision of about one milliarcsecond, with high-quality measurements only for about 100,000 objects within about 200 parsecs (650 light-years) of the solar system. (A single arc second is a very small angular slice of the heavens, making Hipparcos's milliarcsecond precision all the more noteworthy. The moon, for instance, takes up about 1,800 arc seconds in Earth's sky.) As impressive as Hipparcos was, Gaia shattered the records set by its precursor—although not without challenges, such as precision-threatening sprays of stray light that leaked around the edges of the spacecraft's sun shield and through a hole punched by an errant micrometeoroid. But ultimately, Brown says, Gaia's measurements achieved on the order of 100 times greater precision—reaching about 10 microarcseconds. And within the Milky Way, the spacecraft's view encompassed 100 times more volume and included 10 times more targets. The numbers underpinning Gaia are so alien to everyday experience that they border on nonsensical, says Michael Perryman, a former ESA researcher, who has served as project scientist for Hipparcos and Gaia and played a crucial developmental role for both missions. He likens Hipparcos's precision to discerning a second's worth of growth of a human hair from a distance of one meter. Gaia's 100-times-better view, he says, is more like measuring the width of a single hydrogen atom from the same distance. Another comparison involves the size of the two missions' datasets. When the Hipparcos team printed out its complete catalog, Perryman recalls, it comprised five thick volumes—almost enough to fill a single shelf of a bookcase. Printing out the full Gaia catalog with the same density of information per page, he says, would require about 10 kilometers of shelf space. 'The mind boggles,' he says. 'It's almost incomprehensible; these are numbers and dimensions we're simply not equipped to visualize, so even the analogies are very difficult to grasp.' The best example of the heights such precision can reach may be Gaia's tour de force determination of the solar system's acceleration with respect to a vast, sky-encompassing field of quasars. Quasars are the conspicuously bright cores of remote galaxies that harbor actively feeding supermassive black holes. As such, quasars are among the most powerful beacons astronomers can use to probe distant regions of the universe. Gaia pinpointed the positions of more than one and a half million of them to establish a fixed backdrop of sorts, against which various minuscule motions of our solar system or other nearby celestial objects could be seen. One motion Gaia managed to measure was an astonishingly small acceleration of just 0.232 nanometer per second squared—a continuous atom-scale deflection in the solar system's 220-kilometer-per-second trajectory through the Milky Way, attributed to the gravitational pull from our galaxy's center some 26,000 light-years away. Writ large, the displacement adds up to less than a meter per day—and essentially reflects the real-time sculpting of our galactic orbit as the solar system carves a path through the Milky Way's gravitational field. 'It's an almost circular motion around the galactic center, and it's directed toward the supermassive black hole there,' says astronomer Sergei Klioner of Germany's Dresden University of Technology, who led much of the work behind the measurement. 'No other observational data could come anywhere close to competing with Gaia here.... You often hear the term 'astronomical' in the sense of something being very large—but this is an example where Gaia has shown us something that's astronomically small.' Now that Gaia has gone dark, there's already talk of what comes next. 'Do we really need another astrometry mission?' asks Brown, who first began working on Gaia in 1997. 'Well, not immediately, but the extremely precise stellar reference frame it gave us—upon which many other observatories depend—will eventually deteriorate because all the stars are moving, right?' ESA is envisioning a follow-on mission, which would potential launching in the 2040s. This time that mission would be optimized for infrared observations to allow astronomers to see through the dust that otherwise clouds their view of the Milky Way's star-packed disk and galactic center. 'It's, in a way, wonderful but also a bit sad that people take Gaia for granted because, my God, it was a tough mission,' Perryman reflects. 'I don't feel sadness that it's gone; I'm just delighted and relieved it lasted so long, and I'm very conscious of how remarkable it is that we live in a time when society is willing to pool its resources to support such things, and we have the technology in place to do them. I hope this period continues—but I worry we've been taking that for granted, too.'
Fast Company
7 days ago
- Science
- Fast Company
How a planetarium show discovered a spiral at the edge of our solar system
If you've ever flown through outer space, at least while watching a documentary or a science fiction film, you've seen how artists turn astronomical findings into stunning visuals. But in the process of visualizing data for their latest planetarium show, a production team at New York's American Museum of Natural History made a surprising discovery of their own: a trillion-and-a-half mile long spiral of material drifting along the edge of our solar system. 'So this is a really fun thing that happened,' says Jackie Faherty, the museum's senior scientist. Last winter, Faherty and her colleagues were beneath the dome of the museum's Hayden Planetarium, fine-tuning a scene that featured the Oort cloud, the big, thick bubble surrounding our Sun and planets that's filled with ice and rock and other remnants from the solar system's infancy. The Oort cloud begins far beyond Neptune, around one and a half light years from the Sun. It has never been directly observed; its existence is inferred from the behavior of long-period comets entering the inner solar system. The cloud is so expansive that the Voyager spacecraft, our most distant probes, would need another 250 years just to reach its inner boundary; to reach the other side, they would need about 30,000 years. The 30-minute show, Encounters in the Milky Way,
CNN
11-06-2025
- Science
- CNN
Accidental find in planetarium show could shift scientists' understanding of our solar system
CNN — An accidental discovery might change how we think about one of the most mysterious structures in our solar system. The Oort Cloud, a large expanse of icy bodies revolving around the sun at a distance 1,000 times greater than the orbit of Neptune, is widely thought to be spherical — although it has never been directly observed. But during the preproduction of a show titled 'Encounters in the Milky Way,' which debuted Monday at the Hayden Planetarium in New York City, a projection on the planetarium's dome revealed something strange within the Oort Cloud: a spiral. The curators were testing out a scene in September that includes a detailed view of Earth's celestial neighborhood — from the sun to the solar system's outer edges — and were surprised when they saw the structure, which looked coincidentally similar to a spiral galaxy such as our own. 'We hit play on the scene, and immediately we saw it. It was just there,' recalled Jackie Faherty, an astrophysicist at the American Museum of Natural History and the curator of the show. 'I was confused and thought that was super weird. I didn't know if it was an artifact, I didn't know if it was real.' To investigate, Faherty got in touch with David Nesvorny, an institute scientist with the Southwest Research Institute in Boulder, Colorado, and the Oort Cloud expert who had provided scientific data for the scene. 'We didn't create it — David did,' Faherty said. 'This is David's simulation, and it's grounded in physics. It has a totally good physical explanation for why it should be there.' At first, Nesvorny suspected artifacts — abnormalities or distortions in the data visualization — but once he looked at his data, he confirmed the presence of the spiral and eventually published a scientific paper about the discovery in April in The Astrophysical Journal. 'Weird way to discover things,' he said. 'I should know my data better, after years of working with it.' Crazy, long orbits The existence of the Oort Cloud was first proposed in 1950 by Dutch astronomer Jan Oort, who imagined it as a shell of icy bodies swirling around the sun from up to 1.5 light-years away. The cloud is the most distant region in our solar system, stretching as much as halfway to the next star, according to NASA. It's composed of leftovers from the making of our solar system, which were scattered in every direction by the planets after they formed. That means many of the icy bodies in the Oort Cloud don't share the same orbital plane as the solar system itself but travel at various inclinations, which is why the Oort Cloud is pictured as a sphere. If one of those icy bodies gets flung inward toward the sun, the heat starts vaporizing some of the material in the body, creating a tail — and what we call a comet. 'Every now and again, some of these icy bodies come into the inner solar system, and we can see the orbit that they're on,' Faherty said. 'And they're on these really crazy, long orbits. It can take them millions of years to go around the sun. And when they come in, they help us understand how far away they may have come from.' The problem with trying to imagine what the Oort Cloud looks like is that scientists have never seen it, even though we are technically surrounded by it. That's because the bodies that make it up are small — fewer than 60 miles (97 kilometers) in diameter — and even though they potentially number in the trillions, they are far away, making observations with telescopes difficult. The spiral was hiding in Nesvorny's data because he had never thought of visualizing it three-dimensionally. 'I never looked at it in Cartesian coordinates — I didn't have a good reason to do so,' he said. 'But once you do that, it's obvious. It's there.' The galactic tide To confirm the findings, Nesvorny used one of the most powerful computers in the world, NASA's Pleiades Supercomputer, to run simulations that took weeks to complete. 'I thought, maybe just this particular simulation (I gave the planetarium) is showing it, and all the other simulations with other stellar encounters, other parameters, will not show it, in which case it wouldn't be so interesting,' he said. 'But all the simulations, all the models I have, show the spiral.' The reason it's there, he said, is that objects in the Oort Cloud are far away enough from the sun's gravity that they also start being affected by the galactic tide — the gravitational field of our galaxy, exerted by the stars and the dark matter in it. This field is acting on the small bodies and comets in the Oort Cloud by twisting their orbital planes to create a spiral. The spiral, Nesvorny added, is in the inner part of the Oort Cloud, the closest to us, and he still believes that the outer portion is spherical or shell-shaped. The problem of observing the Oort Cloud remains, even though the Vera C. Rubin Observatory, a powerful telescope that recently came online in Chile, could offer a hand by discovering and observing individual icy bodies in the cloud. However, according to Nesvorny, the telescope will likely discover dozens of these bodies — not the hundreds that would be required to produce a meaningful visualization of the spiral. The spiral theory helps to illuminate the dynamics of our solar system, according to Faherty. 'If you're going to come up with a theory of how solar systems evolve, you should take into account the kind of shapes you might have in their structure,' she said. 'Maybe comets helped deliver water to Earth. Maybe the building blocks of life could be out there in the Oort Cloud, so if you want to talk about the potential building blocks of life that surround our solar system, you need to understand its shape.' It's a 'dream,' she added, to be able to present science so recent in a show aimed at the general public. 'I truly believe that the planetarium, the dome itself, is a research tool,' Faherty said. 'I like to say that this is science that hasn't had time to reach your textbook yet.' Viewing what's not visible The spiral finding is a wonderful example of just how much we can learn through visualizing the universe in new ways, said Malena Rice, an assistant professor of astronomy at Yale University who did not participate in the study. 'This result reshapes our mental image of our home solar system, while also providing a new sense for what extrasolar systems' Oort clouds may look like,' Rice added. 'It unites our models of the solar system with what we know about the broader galaxy, placing it into context as a dynamic system. We are not static, and we are not isolated — our solar system is shaped by its broader ecosystem, and the Oort spiral exemplifies that.' While the paper is interesting, it is almost entirely theoretical, as it is based on numerical simulations of the interactions between the sun's gravity and the gravitational pull of the rest of the Milky Way galaxy's motion, said Edward Gomez, an astrophysicist and honorary lecturer at Cardiff University in the UK. He also was not involved with the study. 'Long period comets enter the inner solar system at a range of angles, which the authors try to model using their spiral arm idea,' Gomez said in an email. 'What they are proposing could be true, but it could also be modelled by other shapes of the Oort cloud or physical processes. How to test this is their major issue, because only a handful of potential Oort cloud objects are known about.' Confirming the findings will be a challenge, noted Simon Portegies Zwart, a professor of numerical star dynamics at Leiden University in the Netherlands who was not part of the team behind the research. 'It is interesting that they found the spiral, (but) it seems unlikely that we are going to witness (it) in the foreseeable future,' he said. With luck, he added, the Vera Rubin observatory will detect a few hundred inner Oort Cloud objects, but the spiral would only be visible if many more are found: 'It therefore seems unlikely to be a clearly detectable structure.'
CTV News
10-06-2025
- Science
- CTV News
Astronomy show accidentally reveals unseen structure in our solar system
The Oort Cloud, an expanse of icy bodies in the far reaches of our solar system, is shown here in a scene from "Encounters in the Milky Way," a show at New York City's Hayden Planetarium that spawned an accidental discovery about the cloud's shape. AMNH via CNN Newsource An accidental discovery might change how we think about one of the most mysterious structures in our solar system. The Oort Cloud, a large expanse of icy bodies revolving around the sun at a distance 1,000 times greater than the orbit of Neptune, is widely thought to be spherical — although it has never been directly observed. But during the preproduction of a show titled 'Encounters in the Milky Way,' which debuted Monday at the Hayden Planetarium in New York City, a projection on the planetarium's dome revealed something strange within the Oort Cloud: a spiral. The curators were testing out a scene in September that includes a detailed view of Earth's celestial neighborhood — from the sun to the solar system's outer edges — and were surprised when they saw the structure, which looked coincidentally similar to a spiral galaxy such as our own. 'We hit play on the scene, and immediately we saw it. It was just there,' recalled Jackie Faherty, an astrophysicist at the American Museum of Natural History and the curator of the show. 'I was confused and thought that was super weird. I didn't know if it was an artifact, I didn't know if it was real.' To investigate, Faherty got in touch with David Nesvorny, an institute scientist with the Southwest Research Institute in Boulder, Colorado, and the Oort Cloud expert who had provided scientific data for the scene. 'We didn't create it — David did,' Faherty said. 'This is David's simulation, and it's grounded in physics. It has a totally good physical explanation for why it should be there.' At first, Nesvorny suspected artifacts — abnormalities or distortions in the data visualization — but once he looked at his data, he confirmed the presence of the spiral and eventually published a scientific paper about the discovery in April in The Astrophysical Journal. 'Weird way to discover things,' he said. 'I should know my data better, after years of working with it.' Crazy, long orbits The existence of the Oort Cloud was first proposed in 1950 by Dutch astronomer Jan Oort, who imagined it as a shell of icy bodies swirling around the sun from up to 1.5 light-years away. The cloud is the most distant region in our solar system, stretching as much as halfway to the next star, according to NASA. Spiral structure The spiral structure, visible here behind the sun in a scene from the show, surprised scientists and animators when they saw it projected on the planetarium's dome during preproduction. AMNH via CNN Newsource It's composed of leftovers from the making of our solar system, which were scattered in every direction by the planets after they formed. That means many of the icy bodies in the Oort Cloud don't share the same orbital plane as the solar system itself but travel at various inclinations, which is why the Oort Cloud is pictured as a sphere. If one of those icy bodies gets flung inward toward the sun, the heat starts vaporizing some of the material in the body, creating a tail — and what we call a comet. 'Every now and again, some of these icy bodies come into the inner solar system, and we can see the orbit that they're on,' Faherty said. 'And they're on these really crazy, long orbits. It can take them millions of years to go around the sun. And when they come in, they help us understand how far away they may have come from.' The problem with trying to imagine what the Oort Cloud looks like is that scientists have never seen it, even though we are technically surrounded by it. That's because the bodies that make it up are small — fewer than 60 miles (97 kilometers) in diameter — and even though they potentially number in the trillions, they are far away, making observations with telescopes difficult. The spiral was hiding in Nesvorny's data because he had never thought of visualizing it three-dimensionally. 'I never looked at it in Cartesian coordinates — I didn't have a good reason to do so,' he said. 'But once you do that, it's obvious. It's there.' The galactic tide To confirm the findings, Nesvorny used one of the most powerful computers in the world, NASA's Pleiades Supercomputer, to run simulations that took weeks to complete. 'I thought, maybe just this particular simulation (I gave the planetarium) is showing it, and all the other simulations with other stellar encounters, other parameters, will not show it, in which case it wouldn't be so interesting,' he said. 'But all the simulations, all the models I have, show the spiral.' The reason it's there, he said, is that objects in the Oort Cloud are far away enough from the sun's gravity that they also start being affected by the galactic tide — the gravitational field of our galaxy, exerted by the stars and the dark matter in it. This field is acting on the small bodies and comets in the Oort Cloud by twisting their orbital planes to create a spiral. The spiral, Nesvorny added, is in the inner part of the Oort Cloud, the closest to us, and he still believes that the outer portion is spherical or shell-shaped. The problem of observing the Oort Cloud remains, even though the Vera C. Rubin Observatory, a powerful telescope that recently came online in Chile, could offer a hand by discovering and observing individual icy bodies in the cloud. However, according to Nesvorny, the telescope will likely discover dozens of these bodies — not the hundreds that would be required to produce a meaningful visualization of the spiral. The spiral theory helps to illuminate the dynamics of our solar system, according to Faherty. 'If you're going to come up with a theory of how solar systems evolve, you should take into account the kind of shapes you might have in their structure,' she said. 'Maybe comets helped deliver water to Earth. Maybe the building blocks of life could be out there in the Oort Cloud, so if you want to talk about the potential building blocks of life that surround our solar system, you need to understand its shape.' Vera C. Rubin Observatory The Vera C. Rubin Observatory, located in the Tololo hill near La Serena, Chile, will survey the night sky during its 10-year mission and could greatly expand scientists' understanding of the Oort Cloud. Javier Torres/AFP/Getty Images via CNN Newsource It's a 'dream,' she added, to be able to present science so recent in a show aimed at the general public. 'I truly believe that the planetarium, the dome itself, is a research tool,' Faherty said. 'I like to say that this is science that hasn't had time to reach your textbook yet.' Viewing what's not visible The spiral finding is a wonderful example of just how much we can learn through visualizing the universe in new ways, said Malena Rice, an assistant professor of astronomy at Yale University who did not participate in the study. 'This result reshapes our mental image of our home solar system, while also providing a new sense for what extrasolar systems' Oort clouds may look like,' Rice added. 'It unites our models of the solar system with what we know about the broader galaxy, placing it into context as a dynamic system. We are not static, and we are not isolated — our solar system is shaped by its broader ecosystem, and the Oort spiral exemplifies that.' While the paper is interesting, it is almost entirely theoretical, as it is based on numerical simulations of the interactions between the sun's gravity and the gravitational pull of the rest of the Milky Way galaxy's motion, said Edward Gomez, an astrophysicist and honorary lecturer at Cardiff University in the UK. He also was not involved with the study. 'Long period comets enter the inner solar system at a range of angles, which the authors try to model using their spiral arm idea,' Gomez said in an email. 'What they are proposing could be true, but it could also be modelled by other shapes of the Oort cloud or physical processes. How to test this is their major issue, because only a handful of potential Oort cloud objects are known about.' Confirming the findings will be a challenge, noted Simon Portegies Zwart, a professor of numerical star dynamics at Leiden University in the Netherlands who was not part of the team behind the research. 'It is interesting that they found the spiral, (but) it seems unlikely that we are going to witness (it) in the foreseeable future,' he said. With luck, he added, the Vera Rubin observatory will detect a few hundred inner Oort Cloud objects, but the spiral would only be visible if many more are found: 'It therefore seems unlikely to be a clearly detectable structure.'
Yahoo
10-06-2025
- Science
- Yahoo
Astronomy show accidentally reveals unseen structure in our solar system
An accidental discovery might change how we think about one of the most mysterious structures in our solar system. The Oort Cloud, a large expanse of icy bodies revolving around the sun at a distance 1,000 times greater than the orbit of Neptune, is widely thought to be spherical — although it has never been directly observed. But during the preproduction of a show titled 'Encounters in the Milky Way,' which debuted Monday at the Hayden Planetarium in New York City, a projection on the planetarium's dome revealed something strange within the Oort Cloud: a spiral. The curators were testing out a scene in September that includes a detailed view of Earth's celestial neighborhood — from the sun to the solar system's outer edges — and were surprised when they saw the structure, which looked coincidentally similar to a spiral galaxy such as our own. 'We hit play on the scene, and immediately we saw it. It was just there,' recalled Jackie Faherty, an astrophysicist at the American Museum of Natural History and the curator of the show. 'I was confused and thought that was super weird. I didn't know if it was an artifact, I didn't know if it was real.' To investigate, Faherty got in touch with David Nesvorny, an institute scientist with the Southwest Research Institute in Boulder, Colorado, and the Oort Cloud expert who had provided scientific data for the scene. 'We didn't create it — David did,' Faherty said. 'This is David's simulation, and it's grounded in physics. It has a totally good physical explanation for why it should be there.' At first, Nesvorny suspected artifacts — abnormalities or distortions in the data visualization — but once he looked at his data, he confirmed the presence of the spiral and eventually published a scientific paper about the discovery in April in The Astrophysical Journal. 'Weird way to discover things,' he said. 'I should know my data better, after years of working with it.' The existence of the Oort Cloud was first proposed in 1950 by Dutch astronomer Jan Oort, who imagined it as a shell of icy bodies swirling around the sun from up to 1.5 light-years away. The cloud is the most distant region in our solar system, stretching as much as halfway to the next star, according to NASA. It's composed of leftovers from the making of our solar system, which were scattered in every direction by the planets after they formed. That means many of the icy bodies in the Oort Cloud don't share the same orbital plane as the solar system itself but travel at various inclinations, which is why the Oort Cloud is pictured as a sphere. If one of those icy bodies gets flung inward toward the sun, the heat starts vaporizing some of the material in the body, creating a tail — and what we call a comet. 'Every now and again, some of these icy bodies come into the inner solar system, and we can see the orbit that they're on,' Faherty said. 'And they're on these really crazy, long orbits. It can take them millions of years to go around the sun. And when they come in, they help us understand how far away they may have come from.' The problem with trying to imagine what the Oort Cloud looks like is that scientists have never seen it, even though we are technically surrounded by it. That's because the bodies that make it up are small — fewer than 60 miles (97 kilometers) in diameter — and even though they potentially number in the trillions, they are far away, making observations with telescopes difficult. The spiral was hiding in Nesvorny's data because he had never thought of visualizing it three-dimensionally. 'I never looked at it in Cartesian coordinates — I didn't have a good reason to do so,' he said. 'But once you do that, it's obvious. It's there.' To confirm the findings, Nesvorny used one of the most powerful computers in the world, NASA's Pleiades Supercomputer, to run simulations that took weeks to complete. 'I thought, maybe just this particular simulation (I gave the planetarium) is showing it, and all the other simulations with other stellar encounters, other parameters, will not show it, in which case it wouldn't be so interesting,' he said. 'But all the simulations, all the models I have, show the spiral.' The reason it's there, he said, is that objects in the Oort Cloud are far away enough from the sun's gravity that they also start being affected by the galactic tide — the gravitational field of our galaxy, exerted by the stars and the dark matter in it. This field is acting on the small bodies and comets in the Oort Cloud by twisting their orbital planes to create a spiral. The spiral, Nesvorny added, is in the inner part of the Oort Cloud, the closest to us, and he still believes that the outer portion is spherical or shell-shaped. The problem of observing the Oort Cloud remains, even though the Vera C. Rubin Observatory, a powerful telescope that recently came online in Chile, could offer a hand by discovering and observing individual icy bodies in the cloud. However, according to Nesvorny, the telescope will likely discover dozens of these bodies — not the hundreds that would be required to produce a meaningful visualization of the spiral. The spiral theory helps to illuminate the dynamics of our solar system, according to Faherty. 'If you're going to come up with a theory of how solar systems evolve, you should take into account the kind of shapes you might have in their structure,' she said. 'Maybe comets helped deliver water to Earth. Maybe the building blocks of life could be out there in the Oort Cloud, so if you want to talk about the potential building blocks of life that surround our solar system, you need to understand its shape.' It's a 'dream,' she added, to be able to present science so recent in a show aimed at the general public. 'I truly believe that the planetarium, the dome itself, is a research tool,' Faherty said. 'I like to say that this is science that hasn't had time to reach your textbook yet.' The spiral finding is a wonderful example of just how much we can learn through visualizing the universe in new ways, said Malena Rice, an assistant professor of astronomy at Yale University who did not participate in the study. 'This result reshapes our mental image of our home solar system, while also providing a new sense for what extrasolar systems' Oort clouds may look like,' Rice added. 'It unites our models of the solar system with what we know about the broader galaxy, placing it into context as a dynamic system. We are not static, and we are not isolated — our solar system is shaped by its broader ecosystem, and the Oort spiral exemplifies that.' While the paper is interesting, it is almost entirely theoretical, as it is based on numerical simulations of the interactions between the sun's gravity and the gravitational pull of the rest of the Milky Way galaxy's motion, said Edward Gomez, an astrophysicist and honorary lecturer at Cardiff University in the UK. He also was not involved with the study. 'Long period comets enter the inner solar system at a range of angles, which the authors try to model using their spiral arm idea,' Gomez said in an email. 'What they are proposing could be true, but it could also be modelled by other shapes of the Oort cloud or physical processes. How to test this is their major issue, because only a handful of potential Oort cloud objects are known about.' Confirming the findings will be a challenge, noted Simon Portegies Zwart, a professor of numerical star dynamics at Leiden University in the Netherlands who was not part of the team behind the research. 'It is interesting that they found the spiral, (but) it seems unlikely that we are going to witness (it) in the foreseeable future,' he said. With luck, he added, the Vera Rubin observatory will detect a few hundred inner Oort Cloud objects, but the spiral would only be visible if many more are found: 'It therefore seems unlikely to be a clearly detectable structure.'
