(152830) Dinkinesh
Dinkinesh and Selam are the smallest of Lucy's targets, measuring only about 700 m (0.5 miles) and 200 m (0.15 miles) in diameter, respectively. This encounter was added to the Lucy tour in January 2023 to provide an early test of Lucy's instruments, especially the terminal tracking system. Based on the Lucy observations in the weeks leading up to the encounter, the team began to suspect that Dinkinesh might be a binary. But no one was sure until the first encounter images came down! This small main belt asteroid is an interesting link between the main belt asteroids visited by other spacecraft (which have all been larger than Dinkinesh), and the near-Earth asteroids visited by spacecraft (which have all been more similar in size to Dinkinesh).
Based on the observations from Lucy in the weeks leading up to the encounter, the team began to suspect that Dinkinesh might be a binary, due to its "wonky" light curve. But no one was sure until the resolved encounter images came down, and turns out there is a satellite, a contact binary satellite in particular!
Credit: NASA/Goddard/SwRI/Johns Hopkins APL
Credit: SwRI
They are not just shapeless piles of rock and dust! There are geologic formation indicating internal strength and a complex history.
Credit: SwRI, original image: NASA/Goddard/SwRI/JHU-APL/NOIR
Both lobes of Selam are the same uniform color as Dinkinesh, consistent with forming as material spun off of Dinkinesh.
Credit: SwRI, original image: NASA/Goddard/SwRI
This small asteroid provides insight to how asteroids evolve. This is the smallest main belt asteroid ever visited by a spacecraft, much more similar in size to the near-Earth asteroids recently seen by the Hyabusa, DART and OSIRIS REx spacecraft. Dinkinesh mayprovide insight into how asteroids change when they leave the Main Asteroid Belt and become Near-Earth Asteroids.
SwRI/S. Marchi
This system kept the asteroid in view during the high-speed encounter, allowing the spacecraft to collect more data.
NASA/Goddary/SwRI/JHU-APL
As a spacecraft approaches an asteroid at high speed it is very hard to know exactly how far away the asteroid is. To make sure that the spacecraft doesn’t miss the asteroid, traditionally spacecraft will take a lot of images where the asteroid “might” be, which end up just being images of deep space. Lucy has a system that autonomously tracks the position of the asteroid and keeps it in the field of view, allowing many more images to be taken of the target. However, this system is new and the team wants to test it out on this small asteroid well in advance of the Trojan asteroid encounters.
SwRI
Dinkinesh is the Ethopian name for the ancient hominin fossil commonly known as "Lucy"; it means “you are marvelous” in Amharic. Its satellite, Selam, is named after a fossil of a hominin child sometimes called “Lucy’s baby.” The word is an Amharic greeting meaning “peace”.
The “moonrise” of the satellite, Selam, as it emerges from behind asteroid Dinkinesh as seen by the Lucy Long-Range Reconnaissance Imager (L’LORRI), one of the most detailed images returned by NASA’s Lucy spacecraft during its flyby of the asteroid binary. This image was taken at 12:55 EDT (1655 UTC) Nov. 1, 2023, within a minute of closest approach, from a range of approximately 270 miles (430 km). From this perspective, the satellite is behind the primary asteroid. The image has been sharpened and processed to enhance contrast.
Credit: NASA/Goddard/SwRI/Johns Hopkins APL/NOIR
A series of images of the binary asteroid pair, Dinkinesh and Selam, as seen by the terminal tracking camera (T2CAM) on NASA’s Lucy spacecraft during its closest approach on Nov. 1, 2023. The images were taken 13 seconds apart. The apparent motion of the two asteroids is due to the motion of the spacecraft as it flew past at 10,000 mph (4.5 km/s). These images have been sharpened and processed to enhance contrast.
Credit: NASA/Goddard/SwRI/ASU
A top-down, Solar System view showing Lucy's trajectory during the Dinkinesh encounter on November 1, 2023. White: asteroids that Lucy will fly by. Grey: select other Trojan asteroids. Blue: Earth. Red: Lucy spacecraft. Orange: Jupiter.
Credit: SwRI
Banner Image: The Dinkinesh encounter insignia, the skull of the Lucy fossil with the Lucy spacecraft overlayed the eyes. Credit: Goddard/SwRI