Spiral Structure Discovered in Distant Oort Cloud

Planetarium Projection Reveals Unexpected Shape in Solar System’s Outer Reaches

A surprising discovery during preparations for a new planetarium show suggests the Oort Cloud, a vast reservoir of icy bodies surrounding our sun, may not be spherical as previously thought. A spiral structure was unexpectedly revealed within the cloud during simulations.

Accidental Revelation

The unusual shape appeared during preproduction of “Encounters in the Milky Way,” which debuted Monday at the Hayden Planetarium in New York City. Curators were testing a detailed visualization of our solar system’s outer limits in September when the spiral became visible.

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 show’s curator. 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.

Expert Confirmation

Faherty contacted David Nesvorny, an institute scientist at the Southwest Research Institute in Boulder, Colorado, and an expert on the Oort Cloud, who had provided the scientific data for the simulation. Initial suspicions of a data artifact were quickly dismissed when Nesvorny confirmed the spiral’s presence and subsequently published a paper on the finding in The Astrophysical Journal in April.

We didn’t create it — David did, Faherty explained. This is David’s simulation, and it’s grounded in physics. It has a totally good physical explanation for why it should be there.

Understanding the Oort Cloud

First proposed in 1950 by Dutch astronomer Jan Oort, the Oort Cloud is estimated to extend up to 1.5 light-years from the sun, containing remnants from the solar system’s formation. It’s believed to hold trillions of icy bodies, many less than 60 miles in diameter, making direct observation extremely difficult. Comets originate from this region when icy bodies are drawn closer to the sun.

According to NASA, the Oort Cloud is so distant that sunlight takes over a year to reach its inner edge. This vastness makes studying it a significant challenge for astronomers.

Galactic Influence

Nesvorny’s simulations, run on NASA’s Pleiades Supercomputer, revealed that the spiral structure is likely caused by the galactic tide—the gravitational influence of the Milky Way galaxy on the Oort Cloud’s objects. This force twists the orbital planes of these icy bodies, creating the observed spiral pattern. The spiral is located in the inner portion of the Oort Cloud, while the outer regions are still believed to be more spherical.

Future Observations

While the discovery is based on simulations, the upcoming Vera C. Rubin Observatory in Chile offers potential for observational confirmation. However, Nesvorny notes that observing enough icy bodies—hundreds rather than dozens—will be necessary to visualize the spiral definitively. As of 2024, astronomers have only confirmed the existence of a few dozen objects originating from the Oort Cloud. (Space.com, February 2024)

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.

This finding highlights the dynamic nature of our solar system and its connection to the broader galaxy, offering a new perspective on the potential shapes and structures within other star systems.

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, said Malena Rice, an assistant professor of astronomy at Yale University.

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.

Correction: A previous version of this story misidentified an image of a different telescope as the Vera C. Rubin Observatory.