---
title: An Asteroid Thought to Be One Body Appears to Be Three
description: New images of asteroid (44) Nysa show two valleys wrapping right around it, and a moon about a kilometer across that had never been catalogued.
author: Darie Nani (Editor-in-Chief)
updated: 2026-07-30T01:25:59.579Z
canonical: https://www.sovereignmagazine.com/article/asteroid-44-nysa-three-lobes-hidden-moon
image: https://cdn.nanimediahouse.com/asteroid-44-nysa-three-lobes-moon-67957.webp
categories: Science & Tech
content_type: News
region: Global
publication: Sovereign Magazine
schema_type: Article
---

For more than a hundred years, asteroid (44) Nysa has been one of the easiest targets in the main belt to point a telescope at and one of the hardest to make sense of. It is the brightest of its compositional class, and among the first asteroids to have a rotation period measured from light curves, in 1920. Every attempt to pin down its shape returned something stretched and irregular, the profile astronomers associate with large binary systems, without ever resolving what was actually there.

New images taken with two of the world's largest ground telescopes suggest the reason. Two dark valleys appear to run the whole way around the asteroid, and the team that took the images reads them as necks connecting three separate lobes. Their paper, ["Unmasking (44) Nysa: Evidence for a trilobate structure"](https://arxiv.org/abs/2607.25786), has been accepted as a letter by the journal Astronomy & Astrophysics.

"The images reveal a remarkably unusual object," said Kate Minker of Lowell Observatory, the lead author. "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."

That pair of readings is the honest state of the evidence, and the team has been careful to keep both open. What is not in doubt is the shape itself. Working from the images plus photometric light curves collected at observatories around the world, the researchers built a three-dimensional model that gives Nysa a volume-equivalent diameter of 75 kilometers and a rotation period of 6.4214175 hours.

## Two shadowed valleys run right around it

The features that changed the picture are two shadowed regions, one near the center of the object and one close to its narrowest point. Both appear in multiple viewing geometries, both appear to encircle the asteroid completely, and both are bounded by indentations at the edges. The team interprets them as colli, the neck-like joins between lobes.

Objects of this kind are not new. Toutatis and (486958) Arrokoth were both resolved as contact binaries, two components meeting at a neck. Nysa is notably larger than either, and its central concavity is far more extreme than anything previously observed. If it really is a single coherent body rather than three joined ones, it has to be sturdy enough to hold a shape that looks as though it should not survive.

## The moon turned up in the leftovers

The second finding came out of the image processing rather than the images. Removing the bright halo around an asteroid leaves residuals, and in those residuals, across more than one dataset, sat a faint point of light.

"These observations had to be combined with specially developed image processing techniques to further sharpen the images and remove the bright halo surrounding the asteroid, potentially hiding faint companions," said Anthony Berdeu, one of the lead authors.

Detecting it took a method imported from a different corner of astronomy. "We borrowed a specialized technique from another field of astronomy, known as 'high-contrast imaging', to detect the small moon whose faint light was overwhelmed by the intense brightness of the primary asteroid," said Gianluca Li Causi of the SHARK-VIS team at Italy's National Institute for Astrophysics.

The object sat at a projected separation of 180 kilometers in February and 170 kilometers in March, and stayed put in a Nysa-centered frame for over three hours on each occasion, which rules out a background star drifting through the field. It is roughly a kilometer across and now carries the temporary designation S/2026 (44) 1.

The images came from the Italian SHARK-VIS instrument on the Large Binocular Telescope on Mount Graham in Arizona, and from SPHERE/ZIMPOL on the European Southern Observatory's Very Large Telescope in Chile. Both correct for the blurring the atmosphere introduces. SHARK-VIS adds a fast, very low noise camera that records what amounts to slow-motion footage, freezing the distortion frame by frame so it can be processed out afterwards.

"These observations likely represent the closest competition to spacecraft-quality imaging ever achieved from the ground," Minker said.

## The moon is how they will settle it

Two explanations are on the table for how Nysa ended up this way. In one, fragments from an ancient collision came back together at low speed, possibly before the asteroid arrived where it now sits in the belt. In the other, Nysa is what was left of a larger parent body after a hit-and-run collision.

Tracking the new moon is how the researchers expect to choose. An orbit gives them Nysa's mass, mass with the shape model gives them density, and density is what separates a loose reaccumulated pile from a rigid body that took a beating and held together.

There is a reason to want the answer. Nysa belongs to the E-type asteroids, whose surfaces match the signature of enstatite, an iron-free mineral, and which are linked to the aubrite and enstatite chondrite meteorites. Their chemistry points to formation close to the sun, from the same feedstocks that went into the terrestrial planets, which makes an E-type body a record of the inner solar system's earliest phase. Nysa is one of the largest known, with a reported albedo somewhere between 0.41 and 0.55.

"These new images appear consistent with several earlier clues that Nysa is really a unique object," said Al Conrad of the Large Binocular Telescope Observatory. "For the first time, we can directly investigate whether those clues point to a deeply indented body or to a true multi-lobed structure."

The work involved researchers from Lowell Observatory, the European Southern Observatory, Italy's National Institute for Astrophysics, Charles University in the Czech Republic, the Large Binocular Telescope Observatory, the Universite Cote d'Azur and CNRS in France, the Florida Space Institute at the University of Central Florida, and the University of Liege in Belgium.

More on the observatory's work is at [lowell.edu](https://lowell.edu).

## FAQ

**Q: What are binary asteroids?**
A binary asteroid is a system of two bodies rather than one, a larger primary with a smaller companion orbiting it. Nysa qualifies on that count: the paper concludes it is a binary system, with the 75 kilometer primary and the newly detected object about a kilometer across.

**Q: What is an example of a contact binary?**
Toutatis and (486958) Arrokoth are the standard examples, asteroids whose two components sit joined at a narrow neck rather than orbiting apart. Nysa is larger than both, and the indentation running around it is much deeper than anything seen on those objects, which is why the team raises the possibility of three joined components rather than two.