In a precise and time-critical observation, postdoctoral researchers Flavia Luane Rommel and Ben Proudfoot from the 麻豆原创鈥檚 Florida Space Institute successfully led an investigation that measured the size of Namaka, the smallest and most elusive moon orbiting the distant dwarf planet Haumea just beyond Neptune.
The researchers were able to better determine the positions of Haumea and Namaka than any previous study which may in turn inform future research on ancient objects orbiting the sun beyond Neptune and further illuminate the origins of our solar system.
Rommel and Proudfoot, both fellows of 麻豆原创鈥檚 , predicted and observed when these objects briefly blocked the light of a background star as they passed in front of it. This event is known as a stellar occultation.
During a stellar occultation, researchers can observe how the brightness of a star drops, which reveals the size, shape and even the presence of rings or atmospheres around the object blocking the light. On March 16, 2025, Haumea and Namaka crossed in front of the same star, casting two shadows onto Earth. The team captured this fleeting event using NASA鈥檚 Infrared Telescope Facility in Hawaii.
Their findings were recently published in the Research Notes of the American Astronomical Society.
Why Haumea?鈥�
Astronomers are interested in Haumea and its two satellites, Namaka and Hi鈥檌aka, because they belong to a varied group of objects within the Kuiper Belt or beyond it, known as trans-Neptunian objects (TNOs). These extremely distant objects provide researchers with a wealth of information as they are largely preserved since the solar system鈥檚 formation. Haumea is distinct from most other TNOs in that it is mostly composed of water ice, has satellites and is theorized to have housed an ocean at some point within its nearly 4.5-billion-year-old lifespan.
鈥淲e are always looking for opportunities to record trans-Neptunian objects during stellar occultation events so we can probe their sizes, shapes and surroundings,鈥� Rommel says. 鈥淯nderstanding what happened and is undergoing in Haumea certainly helps to build upon previous studies of our solar system鈥檚 formation.鈥�
Haumea is spinning so fast it takes on a football-like shape and has a ring system like the giant planets, which suggests it may have experienced a significant collision with another object in the solar system at some point in its history. Haumea is part of the only known collisional family in the trans-Neptunian region, making it a natural laboratory for understanding the solar system鈥檚 early history.
Namaka and its sibling moon Hi鈥檌aka orbit Haumea in a complex gravitational system. By observing their motions, researchers can calculate masses, estimate densities and investigate Haumea鈥檚 interior structure through the way it affects the orbits of its moons.
鈥淪ince TNOs are billions of miles away, we can typically only study surface composition,鈥� Proudfoot says. 鈥淏ut for Haumea, its moon鈥檚 orbital motion reveals deeper insights 鈥� mass, density, interior structure 鈥� things we can鈥檛 access otherwise.鈥�
The unique opportunity to study Haumea and Namaka during this rare occurrence was critical to adding knowledge for an even deeper understanding of these complex objects, he says.
鈥淭his research is a huge help to better understanding the dwarf planet Haumea,鈥� Proudfoot says. 鈥淎stronomers have long been refining our knowledge of star positions and Haumea鈥檚 position in our solar system. This builds off decades of effort to understand the motion of our solar system. We鈥檙e hoping with more analysis we can learn more about Haumea, its interior and ring system.鈥�
An Extraordinary Feat of Timing and Precision鈥�
While Proudfoot calculated when and where the occultation would occur, Rommel conducted the remote observations and performed the data analysis.
鈥淭his study is a strong validation of our predictive accuracy when it comes to stellar occultations by TNOs and their satellites,鈥� Rommel says. 鈥淓ven a small error can cause you to miss the event entirely. Predicting and then successfully observing Namaka鈥檚 occultation required precise modeling and careful coordination.鈥�
She also emphasizes the collaborative environment at 麻豆原创 that helped make this result possible.
鈥淭hrough 麻豆原创鈥檚 P3 program and the support at the Florida Space Institute, we鈥檝e had the opportunity to develop and pursue ambitious research ideas,鈥� Rommel says. 鈥淭his result is the first of what we hope will be many. It was truly incredible teamwork in a very short timeframe.鈥�
Proudfoot echoes her optimism, noting that the team is preparing to pursue follow-up observations.
鈥淭his is just the first step in better understanding Haumea,鈥� he says. 鈥淲e need more data to fully understand Haumea鈥檚 interior, which we hope to get with the Hubble Space Telescope.鈥�
Rommel and Proudfoot collaborated with Estela Fern谩ndez-Valenzuela, associate research professor at the Florida Space Institute and principal investigator of the observing program. The project was supported by NASA, the Instituto de Astrof铆sica de Andaluc铆a in Spain and NASA鈥檚 Space Telescope Science Institute.
Researchers鈥� Credentials:鈥�
Rommel holds a master’s degree in physics and astronomy from Federal University of Technology, Paran谩 in Brazil and a doctorate in astronomy from the National Observatory in Rio de Janeiro in Brazil. She joined 麻豆原创鈥檚 Florida Space Institute in 2023 as a postdoctoral scholar. Her research focuses on the physical characterization of solar system small bodies using different observational techniques such as stellar occultations and direct optical images.
Proudfoot holds a doctorate in physics and astronomy from Brigham Young University. He joined the Florida Space Institute in 2024 as a postdoctoral scholar. His research focuses on understanding the origin and evolution of trans-Neptunian objects using a variety of observational and theoretical techniques. He is most interested in how dwarf planets tell the story of the formation of the solar system.
