Rendering by NASA, ESA, Joseph Olmsted (STScI)
By Abigail Haven
A new study from BYU professor of physics and astronomy Darin Ragozzine and former undergraduate student Maia Nelsen provides new insight into the structure of objects in the Kuiper Belt. Using data from NASA's Hubble Space Telescope, the research suggests that an object previously thought to be a binary system may be a rare triple system of orbiting bodies.
The findings, recently highlighted in a news release from the Space Telescope Science Institute, contribute to the understanding of these distant solar system objects and could offer additional context on the early formation of planetary bodies.
While decades of research have revealed much about the solar system, many aspects remain unclear. In particular, the small, icy objects that orbit beyond Neptune in the “Kuiper Belt” are faint and difficult to study. One object in the Kuiper Belt, known as Altjira, is the the focus of this study.
Over the last 10 years, the Hubble Space Telescope has taken pictures of Altjira and a 2011 study found that it appears as two points of light, making it a “binary” system. Ragozzine and his students took these pictures and used them to track the progression of the orbit.
“Through pictures you can track how they're orbiting each other,” Ragozzine said. “This is valuable, because you can use mathematical equations and solve for what that orbit is like. Is it a circle? Is it an oval? Is it fast? Is it slow? How big is it?”
Ragozzine’s research group is known for going beyond figuring out the general shape of the orbit and finding whether the orbit is changing over time. Orbital changes are stronger when the objects – too small to see even with Hubble – are elongated. As part of her astronomy senior thesis, Nelsen showed that the orbital changes were so strong that they are best explained by Altjira being three objects, making it a rare “triple system.” Ragozzine credits another graduate student, Ben Proudfoot, for receiving a research grant to take new images of Altjira in 2023 using the Hubble Telescope that confirmed the orbital changes.
In a publication led by Nelsen in the Planetary Science Journal, they conclude that Altjira might be one of the only few known triple systems in the Kuiper Belt. However, additional observations will be needed to confirm this interpretation.
“This is an important result because, if confirmed, it would be the second triple system ever discovered in the solar system,” said Nelsen. “It’s hard to observe, but the data suggests this could be something new and extraordinary.”
In the publication, they even provide the roadmap to future confirmation by predicting times when the two main compoments of Altjira might shadow or block each other’s light. There’s already plans to use BYU’s access to the Astrophysical Research Consortium telescope to observe Altjira in October 2025 in order to better understand Altjira and confirm that it is a triple system.
Studying Kuiper Belt objects like Altjira provides researchers with a valuable look at the early solar system. Since these objects remain largely unchanged due to their distance from the Sun, they retain characteristics from their formation billions of years ago.
"Kuiper Belt objects, for the most part, are in the same condition as they were 4.5 billion years ago when the solar system formed," Nelson said. "They are a window into the formation of the solar system and studying how that entire process worked."
Ragozzine emphasized that unlike asteroids, which experience collisions and movement over time, Kuiper Belt objects have remained relatively undisturbed.
"Unlike asteroids which bash into each other and move around, Kuiper Belt objects have never been hit," Ragozzine said. "They've never melted. They were born and then frozen into place. This makes them ancient fingerprints and unique in the whole solar system."
For Nelson, participating in this research as an undergraduate has been a formative experience that has helped shape her career aspirations.
"I never thought that work like this was possible as an undergrad," Nelson says. "I'm super glad BYU invested in building this program for students like me. I want to turn research into a career, and I know this for sure now because I was able to jump right into research early."
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