One of the brightest asteroids in the main belt has turned out to be far stranger than a single lump of rock. New high-resolution images suggest that (44) Nysa, an object studied for more than a century, is built from three connected lobes joined at narrow necks — and that it is orbited by a small moon no one had seen before.
If confirmed, the shape would make Nysa the first known contact trinary, a body assembled from three pieces rather than the two that make up better-known peanut- and snowman-shaped objects. The finding offers a rare look at how violent, slow-motion collisions shaped the early solar system, and at how much detail modern telescopes can now pull from a speck of light tens of millions of miles away.
Two neck-like valleys wrapping around a triple body
An international team reported the result after obtaining the sharpest views ever taken of the asteroid. According to the researchers describing the observations, the images reveal a highly concave object marked by two prominent valleys that appear to wrap around its circumference. The team interprets those grooves as “colli,” or neck-like connections, between separate lobes — the seams where distinct chunks meet. To pin down the three-dimensional form, scientists combined the direct imaging with extensive brightness measurements gathered by observatories worldwide, then built a detailed shape model that supports the presence of three distinct lobes.
Nysa is no minor target. It spans roughly 46 miles across and belongs to a class known as E-type, or enstatite-like, asteroids, whose bright surfaces reflect light in a way that matches an iron-free mineral. Because that composition points to formation close to the young Sun, these bodies may preserve chemical clues from the inner solar system’s earliest days. Lead author Kate Minker of Lowell Observatory said the most likely explanation is that Nysa is either a contact trinary of three joined components or an extraordinarily irregular single body unlike anything observed before.
How two telescopes froze the atmosphere’s blur
Resolving the shape of an object that small at that distance required beating the blurring caused by Earth’s atmosphere. The team drew on the Large Binocular Telescope on Mount Graham in Arizona, using a high-contrast imager called SHARK-VIS together with an adaptive optics system that reshapes a mirror hundreds of times per second to cancel atmospheric turbulence. SHARK-VIS captures rapid, slow-motion footage that effectively freezes the shimmer, then combines frames to reach exceptional sharpness. The instrument’s continuous observations on Feb. 15 produced the most detailed view of Nysa to date.
The Arizona data were paired with images from the SPHERE/ZIMPOL instrument on the European Southern Observatory’s Very Large Telescope in Chile. The Large Binocular Telescope’s light-gathering power comes from a 27-foot primary mirror, about three times the diameter of the Hubble Space Telescope, and its adaptive optics rely on an array of 672 fast actuators that subtly deform a secondary mirror to correct for the sky’s distortions. Together the two observatories delivered images sharper than Hubble could manage for this target. Ground-based telescopes were long considered inferior to space telescopes for fine detail because the atmosphere smears incoming light, but modern adaptive optics has reversed that assumption for many objects, letting large mirrors on Earth exploit their size advantage. Nysa is a demanding test of that capability: it is bright but small on the sky, and pulling a resolved shape from it requires squeezing every bit of performance out of the instruments.
A newly spotted moon and two theories of origin
The observations also turned up a previously unknown satellite, temporarily designated S/2026 (44) 1. In the study describing the trilobate structure, the team estimates the moon is a little over half a mile wide and orbits at least about 105 miles from the asteroid. That companion is more than a curiosity: tracking its orbital speed and period should let astronomers weigh Nysa itself, deriving a mass and density that could help decide between competing accounts of how the odd shape formed.
Two scenarios lead the field. In one, fragments from an ancient collision re-accumulated at low speed, gently sticking together rather than shattering, possibly before Nysa drifted to its current spot in the belt. In the other, the asteroid is the battered remnant of a dramatic hit-and-run impact involving a larger parent body. Either way, the necks between the lobes are the tell — features that record pieces coming together instead of a single mass being carved. Contact binaries, the two-lobed cousins of what Nysa may be, are known elsewhere in the solar system, but a stable three-lobed body would push the idea further and raise fresh questions about how gently three separate masses could meet without breaking apart. Confirming the structure will require additional observations to rule out the alternative that Nysa is simply one deeply dented rock rather than three joined pieces.
Unmasking an object first cataloged in 1857
Nysa has intrigued observers since it was discovered and named in 1857, its unusual brightness and composition marking it as an oddity long before anyone could see its shape. Earlier studies hinted at an elongated or two-lobed form, but the true structure stayed hidden until adaptive optics matured enough to bring it into focus. A co-author on the paper compared the mass-measuring strategy to guessing at a wrapped gift by hefting the box to sense its weight, and therefore its contents.
Should the trinary interpretation hold up under further observation, Nysa would join a small but growing gallery of solar system bodies whose contorted outlines preserve the fingerprints of ancient mergers. For an asteroid whose name nods to a mythological hiding place, the researchers noted, the new images finally begin to strip away the disguise it has worn since the middle of the 19th century.
This article was produced with AI assistance and reviewed by the Morning Overview editorial team.
More from Morning Overview
