Lucy Mission Unveils Twin Moons Orbiting Dinkinesh Asteroid

NASA's Lucy mission unveiled a cosmic surprise during its preliminary asteroid flyover on November 1. The main belt asteroid Dinkinesh, or fondly termed "Dinky," was found to harbor a miniature moon. The surprise doubled when subsequent imaging showed two small satellites closely orbiting, appearing as one due to their proximity.

The scientific community has been studying Dinky, the smallest main belt asteroid ever probed, exhibiting a diameter of roughly 790 meters, since 1999. The peculiar fluctuation in its brightness indicated an unusual nature, but the existence of twin moons was beyond anticipation. The combined circumference of these moons is approximately 720 feet (220 m).

The term "binary contact" describes celestial objects orbiting in close proximity, often forming a peanut or pear shape. Such binary systems, like Arrokoth in the Kuiper belt confirmed by the New Horizons spacecraft in 2019, may be prevalent in our solar system. Several asteroids and comets have also been identified as contact binaries.

An intriguing aspect of Dinkinesh's moons is their similar size, creating a gravitational puzzle for researchers. Most contact binaries are asymmetrical, making this a unique case. Astronomer Hal Levison from the Southwest Research Institute expressed the scientific community's excitement to decipher this mystery.

The Lucy mission's primary focus is far from Dinkinesh; analyzing Jupiter's Trojan asteroids is its ultimate goal. However, the unexpected discovery during the initial asteroid flyover in 2025 was a successful test for Lucy's equipment. Plans are now afoot for Lucy to image another main belt asteroid, Donaldjohanson, during its 2027 flyby.

Dinkinesh was first spotted by Lincoln Near-Earth Asteroid Research (LINEAR) on November 4, 1999. The Minor Planet Center (MPC) published these observations later that month. Further surveillance of Dinkinesh continued until mid-November, after which it went unnoticed for several years.

The NEAT (Near-Earth Asteroid Tracking) survey re-observed Dinkinesh in 2007 as a new asteroid, leading the MPC to allot another provisional designation. However, the correlation between the 1999 and 2007 observations was soon recognized, establishing Dinkinesh as a permanent minor planet catalog number 152830.

The discovery of Dinkinesh's twin moons not only arouses scientific curiosity but also offers a new perspective on our understanding of celestial bodies and their behaviors.