Asteroid (44) Nysa: rare three-lobed rock with its own moon
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- Asteroid (44) Nysa is a rare E-type asteroid rich in enstatite and the brightest of its kind, with an average diameter of about 75 km, orbiting in the main asteroid belt between Mars and Jupiter; it was first spotted in 1857.
- Kate Minker at Lowell Observatory and her colleagues used the Large Binocular Telescope in Arizona and the Very Large Telescope in Chile to reconstruct the asteroid in three dimensions.
- The 3D model shows three distinct lobes joined by thin "necks" — a contact trinary configuration that is far rarer than the already uncommon two-lobed asteroids.
- Formation remains an open question: either repeated collisions battered a once-normal asteroid into its current shape, or three separate bodies merged, in which case the interior must be unusually strong to hold the structure together.
- A tiny moon roughly a kilometre across appears to orbit (44) Nysa, and tracking that orbit in future observations could reveal the asteroid's interior structure and origin story.
Why it matters: Contact trinaries are among the rarest asteroid architectures known, so a 75-kilometre example with its own ~1 km moon gives planetary scientists a natural lab for testing how asteroids survive collisions and accrete — and the moon's orbital mechanics could become the only practical probe of (44) Nysa's otherwise hidden interior.
