Ⓒ NASA/Keegan Barber
Lucy’s primary goal is to survey the Jupiter Trojan asteroids. This first encounter with a small, main belt asteroid was only added to the mission in January 2023, primarily to serve as an in-flight test of the system that allows the spacecraft to continually track and image its asteroid targets as it flies past at high speed.
The Lucy team had wondered if Dinkinesh might be a binary system, given how Lucy’s instruments were seeing the asteroid’s brightness changing with time. The first images from the encounter removed all doubt. Dinkinesh is a close binary. From a preliminary analysis of the first available images, the team estimates that the larger body is approximately 790 m at its widest, while the smaller is about 220 m in size.
In the first images of Dinkinesh and its satellite, which were taken at closest approach (A), the two lobes of the contact binary happened to lie one behind the other from Lucy's point of view. Only when the team downlinked additional images, captured in the minutes around the encounter (B), was the true nature of this object revealed.
Contact binaries seem to be fairly common in the solar system,” said John Spencer, Lucy deputy project scientist, of the Boulder, Colorado, branch of the San-Antonio-based Southwest Research Institute. “We haven’t seen many up-close, and we’ve never seen one orbiting another asteroid. We’d been puzzling over odd variations in Dinkinesh’s brightness that we saw on approach, which gave us a hint that Dinkinesh might have a moon of some sort, but we never suspected anything so bizarre!
Ⓒ NASA/Goddard/SwRI
source: https://www.nasa.gov/news-release/nasas-first-asteroid-sample-has-landed-now-secure-in-clean-room/