Astronomers find asteroid with three lobes and a moon in the main belt
New astronomical observations have revealed that the asteroid 44 Nysa, located in the main belt between Mars and Jupiter, has a surprising structure: three distinct lobes and a small moon in its orbit. This is the first time that a celestial body with such a configuration has been identified in our solar system, challenging previous conceptions about the formation and evolution of asteroids. The discovery, the result of joint work by scientists at important observatories, offers a rare opportunity to deepen understanding of planetary origins.
The complex structure of asteroid 44 Nysa is revealed by advanced observations
Originally discovered in 1857, asteroid 44 Nysa was, until then, considered just a point of light in the sky. Subsequent observations, including data from the Hubble Space Telescope, suggested a bi-lobed shape, similar to other known asteroids and comets. However, a recent collaboration between the Large Binocular Telescope (LBT) on Mount Graham, Arizona, and the Very Large Telescope (VLT) on Paranal Mountain, Chile, has changed this perception.
The new images show an irregularly shaped object measuring about 75 kilometers at its widest point. The surface features two “colli”, or valleys, that surround the asteroid, interpreted by the research team as the “connections” between the different lobes. In addition, a moon approximately 1 kilometer wide was identified, orbiting Nysa at a distance of at least 170 kilometers. This satellite has been given the provisional designation S/2026 (44) 1.
Cutting-edge technologies allow us to uncover celestial mysteries
Obtaining such detailed images of Nysa posed a significant challenge for astronomers. The key to success was the use of two high-contrast imaging devices: the Italian-built SHARK-VIS, coupled to the LBT, and the SPHERE, with its ZIMPOL polarimeter, on the VLT. These instruments were used in conjunction with adaptive optics systems.
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The combination of advanced technologies made it possible to neutralize the blurring effect caused by the Earth’s atmosphere. These observations were then complemented by specially developed image processing techniques to further refine the photos and eliminate the bright halo around the asteroid, which could hide faint companions. Kate Minker, lead researcher at Lowell Observatory, described the find as “a remarkably unusual object.” Gianluca Li Causi, from the SHARK-VIS team at the Italian National Institute of Astrophysics (INAF), explained that the team “borrowed a specialized technique from another field of astronomy, known as high-contrast imaging, to detect the small moon.”
Scientists explore the origins of Nysa’s unique form
The formation of an object with three lobes and a moon raises complex questions about dynamic processes in the asteroid belt. Kate Minker’s team proposed two main explanations for Nysa’s peculiar appearance.
The preferred theory suggests that Nysa is a “trinary contact,” that is, three distinct asteroid bodies that are loosely held together by the force of gravity. This configuration implies that the components came together smoothly at some point in their history. The second alternative hypothesis proposes that Nysa had a close encounter with a much larger asteroid in the past.
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In this scenario, the impact would have deformed Nysa, creating her bizarre shape and possibly fragmenting her into a series of pieces. However, this theory faces a challenge: events of this type usually produce a “family” of asteroids with similar composition, but Nysa appears to be an isolated object except for its small moon. To differentiate between the two possible origins, astronomers plan to monitor the speed and orbital period of Nysa’s moon. This data will allow us to determine the exact mass and density of the asteroid, which in turn will help identify which formation model best fits the data.
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Asteroid 44 Nysa as a link to the formation of Earth
Nysa’s importance transcends her strange form. This asteroid could offer valuable information about the formation process of planets, including our own. Nysa is notably more reflective than many other asteroids, a characteristic attributed to its surface composition rich in enstatite, a silicate mineral that does not contain iron.
Asteroids with these characteristics are classified as type E, and Nysa is the largest and brightest of all known. Scientists believe E-type asteroids formed close to the Sun, making them potential “building blocks” for inner planets like Earth. If Nysa is a remnant of that primordial period, it could reveal crucial details about conditions in the inner solar system 4.5 billion years ago. The revelation of her true nature, as Al Conrad of the Large Binocular Telescope Observatory suggested, is like “unmasking the asteroid, long after its discovery,” echoing the Greek god of theater, Dionysus, after whom Nysa was named.
The results of this research were published in the arXiv archive and submitted for publication in the journal Astronomy & Astrophysics, consolidating an important milestone in the understanding of celestial bodies.
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