An asteroid moon discovered by Lucy is itself a double-lobed object.

Lucy's Dinkinesh encounter revealed a satellite, then showed that the satellite itself consists of two connected lobes.

The object is called Selam, and its shape makes it a contact binary rather than a simple rounded moon.

Images from different viewing angles were essential: the first pictures hid one lobe behind the other.

On November 1, 2023, NASA's Lucy spacecraft flew past the small main belt asteroid Dinkinesh. The encounter took place during the mission's journey toward Jupiter's Trojan asteroids. Dinkinesh was not one of those distant Trojan targets. It offered an earlier opportunity to observe an asteroid at close range, and the resulting images revealed a system more complicated than the team had expected.

The first surprise was a moon. The next surprise arrived as additional encounter data reached Earth: that moon was not a single rounded body. It had two lobes in contact. The satellite was named Selam, and NASA described it as the first contact binary discovered orbiting another asteroid. That distinction is narrower than saying it was the first contact binary ever found anywhere in the solar system.

The sequence matters because perspective initially concealed the structure. Near closest approach, the two lobes lay one behind the other along Lucy's line of sight. Pictures taken later, after the spacecraft had moved, separated their outlines. A departure image captured about six minutes after closest approach revealed the contact binary clearly. More data changed the interpretation without requiring the object itself to change.

A contact binary consists of two recognizable components touching each other. That is different from two moons orbiting independently, and different from a pair of separated bodies circling a common center. Selam is a satellite of Dinkinesh, but the satellite has its own double lobed structure. Keeping those levels separate avoids the misleading impression that Lucy simply discovered two ordinary moons beside one asteroid.

The discovery provides a natural laboratory for studying how small bodies acquire complex shapes and companions. Images constrain what exists, while explanations of how it formed require additional analysis and modeling. A touching pair suggests a history of assembly or rearrangement, but a photograph alone does not uniquely reconstruct that history. Scientists must test proposed pathways against the system's geometry and motion.

The encounter also illustrates why flyby missions collect sequences rather than relying on one dramatic portrait. Changing illumination and perspective expose features that overlap in a single frame. Data returned after an encounter can therefore contain major discoveries even when the spacecraft has already moved far beyond its target. For Lucy, a relatively small asteroid became a reminder that unexplored worlds can challenge expectations before a mission reaches its principal destinations.

Dinkinesh shows why small bodies can surprise even a mission whose primary destinations lie elsewhere. Lucy’s flyby revealed structure that a distant unresolved observation could not show. The important discovery was not simply another point beside an asteroid, but the physical arrangement of the satellite itself.

No. They touch and together form one contact binary satellite. The important distinction is between two connected components of one satellite and two bodies following separate orbits around the primary asteroid.

The lobes overlapped along the spacecraft's viewing direction. Later images provided a different perspective and revealed both components, showing how a seemingly simple outline can conceal a more complicated structure.

No. It is in the main asteroid belt between Mars and Jupiter. Lucy encountered it on the broader journey toward the Jupiter Trojan populations that form the mission's principal scientific targets.