Mysterious asteroid 44 Nysa may be the first known three-lobed world. It even has a moon.
In a new study, available on the arXiv preprint server, a team of astronomers has found evidence that the object 44 Nysa, discovered in 1857, is a triple-lobed asteroid with a moon—the first known object of its kind. For the longest time, the 75-km-wide (47-mile-wide) Nysa was a subject of interest due to its unusual brightness and composition, and past observations suggested that it has an elongated or potentially bilobate shape.
The latest findings come from investigations by the Large Binocular Telescope in Arizona and the European Southern Observatory’s Very Large Telescope in Chile. “The images reveal a remarkably unusual object,” lead author Kate Minker of Lowell Observatory said in a statement. “The most likely explanation is that Nysa is either a contact trinary, consisting of three connected components, or an extremely irregular coherent body unlike anything we’ve previously observed.” According to Minker, these images are of the highest quality by ground-based telescopes, rivaling those taken by spacecraft.
Thanks to the cutting-edge technology and advanced image processing, scientists also confirmed the presence of a moon around Nysa. Estimates suggest it measures roughly one kilometer (0.62 miles) in diameter and orbits Nysa from a distance of at least 170 kilometers (106 miles). The moon has been given a temporary designation of S/2026 (44) 1. Study authors say that future observations would help determine Nysa’s mass and density more precisely and ultimately uncover what gave it its current form.
Explaining the shape of Nysa, the study authors have put forth two possible explanations. First is that the asteroid may have deformed through “low-velocity reaccumulation of fragments” after its collision with an ancient object, and second is that it could be a remnant of a “hit-and-run collision involving a larger parent body.” Al Conrad of the Large Binocular Telescope Observatory says that the images hint at Nysa truly being a unique object and that they can help determine if the asteroid is a deeply indented body or a true multi-lobed structure.
Asteroids like Nysa are called E-type (enstatite-like) asteroids. This designation refers to their surface composition, which gives them their bright appearance and matches the light-reflecting signature of the iron-free mineral enstatite. These asteroids, believed to have formed near the Sun, may also share chemical traits with the building blocks of Earth and contain records of the enstatite-rich inner solar system. Understanding Nysa, therefore, could open a window into the processes that were in motion in the early days of our cosmic neighborhood.
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