Astronomers Reveal Asteroid Nysa Is Likely a Contact Trinary with a Small Moon
Images from the Large Binocular and Very Large Telescopes show asteroid Nysa likely has three joined lobes and a tiny moon.
On July 29, 2026, astronomers using the Large Binocular Telescope in Arizona and the Very Large Telescope in Chile captured high‑resolution images of asteroid Nysa. The data reveal a remarkably irregular object that appears to be three lobes fused together, with a tiny satellite orbiting the system. If confirmed, Nysa would become the first known trinary asteroid, reshaping our view of how small bodies coalesce in the main belt.
What happened
Astronomers from Lowell Observatory reported that the new images show three distinct components connected by narrow neck‑like regions, a morphology they term "colli." The observations were published on arXiv on July 28, 2026 and have been accepted by Astronomy & Astrophysics.
In addition to the tri‑lobed shape, a faint point source was detected moving in concert with the main body, interpreted as a tiny moon. Nysa is classified as an E‑type asteroid, rich in enstatite, which gives it a high albedo and a visual magnitude around 6.75—bright enough for binoculars under dark skies.
Why it matters
A confirmed contact trinary challenges existing models that primarily predict binary or single‑body asteroids in the belt. It suggests that low‑velocity collisions can produce more complex aggregates, offering a new laboratory for studying early solar‑system accretion. The presence of a moon also provides a natural probe of the system’s mass and density, informing impact‑risk assessments for similar objects.
- First identified trinary asteroid, expanding taxonomy of small bodies.
- Moon offers a way to measure Nysa’s mass and internal structure.
- High albedo makes the object accessible to amateur observers.
- Current images lack the resolution needed for definitive shape modeling.
- Moon’s size and orbit remain poorly constrained.
- Interpretation relies on a single epoch of observation.
How to think about it
For observers, note that Nysa reaches magnitude ~6.75 near opposition, so a pair of 7×50 binoculars can reveal it as a faint star. Keep an eye on upcoming campaigns from both hemispheres; additional imaging will refine the lobes’ geometry and confirm the moon’s orbit. Researchers should treat Nysa as a case study when updating collisional evolution simulations of the main belt.
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