152830 Dinkinesh
152830 Dinkinesh is a binary main-belt asteroid about in diameter. It was discovered by the Lincoln Near-Earth Asteroid Research survey at Socorro, New Mexico on 4 November 1999. Dinkinesh, the name borrowed from an Ethiopian word for the Lucy fossil, was the first flyby target of NASA's Lucy mission, which approached from the asteroid on 1 November 2023. During the flyby, the Lucy spacecraft discovered that Dinkinesh has a [contact binary asteroid|binary (small Solar System body)|contact-binary] natural satellite, named Selam, which is in diameter. Dinkinesh is the smallest main-belt asteroid explored by spacecraft yet, though some smaller near-Earth asteroids have also been explored.
Discovery and observational history
Dinkinesh was discovered on 4 November 1999 by the Lincoln Near-Earth Asteroid Research sky survey at Socorro, New Mexico. The discovery observations were published by the Minor Planet Center on 23 November 1999 and the asteroid was given the minor planet provisional designation, which describes its discovery year, month, and discovery order within the month. The LINEAR and Spacewatch surveys continued observing Dinkinesh until 15 November 1999, after which the asteroid became lost and went unrecognized for years.On 19 April 2004, Spacewatch reobserved Dinkinesh as a seemingly new asteroid, but misattributed these observations to those of another unrelated asteroid,, which was discovered by the same survey on 12 April 2004. Dinkinesh was again reobserved as a seemingly new asteroid on 15 and 17 February 2007 by Palomar Observatory's Near-Earth Asteroid Tracking survey at San Diego County, California, which led the MPC to give Dinkinesh the provisional designation on 25 February 2007. Gareth V. Williams, the associate director of the MPC at the time, recognized that and were the same asteroid and published the linkage on 2 March 2007. The linkage between Dinkinesh's 1999 and 2007 observations enabled the MPC to find additional observations from 2001 to 2007, where the asteroid was previously detected unknowingly. The linkage and additional observations extended Dinkinesh's observation arc to over 7 years and greatly reduced uncertainties in its orbit. This allowed the MPC to give Dinkinesh its permanent minor planet catalog number 152830 on 2 April 2007. Pre-discovery LINEAR observations of Dinkinesh from 15 October 1999 were later identified and published on 19 August 2007, extending the observation arc by another 5 years.
On 3 March 2007, the MPC established that Spacewatch's 2004 observations of Dinkinesh were not of, and thus redesignated these observations as. However, the MPC did not recognize that was Dinkinesh until Gareth Williams made the linkage and published it on 9 February 2009.
Name
Dinkinesh is the Amharic name for the Lucy fossil, after which NASA's Lucy mission is named. The name means "you are wonderful" in the Amharic language. "Dinkʼi" means "wonderful" and "nesh" means "you are" in feminine form. The asteroid was unnamed when it was selected for exploration by the Lucy spacecraft, so the Lucy mission team proposed the name Dinkinesh to the International Astronomical Union's Working Group for Small Bodies Nomenclature, which approved and announced the name on 6 February 2023.Orbit
Dinkinesh orbits the Sun in the inner main asteroid belt on an elliptical orbit with an average distance of2.19 astronomical units and an orbital period of 3.24 years. With an orbital eccentricity of 0.112, Dinkinesh comes as close as from the Sun at perihelion to as far as at aphelion. The asteroid's orbit is inclined 2.1° with respect to the plane of the Solar System. Dinkinesh is possibly a member of the Flora family, a group of asteroids that share similar orbital characteristics as the family's parent asteroid 8 Flora.
Exploration
The Lucy spacecraft made a flyby of Dinkinesh from a distance of on 1 November 2023 16:54 UTC. Lucys flyby of Dinkinesh was announced by NASA and the Lucy science team on 25 January 2023, more than one year after Lucy had launched in October 2021. The asteroid was initially overlooked as a potential flyby target because it was too small. It was identified in August 2022 by Raphael Marschall, mission collaborator of the Nice Observatory, who investigated 500,000 asteroids for potential close approaches with the spacecraft. The original trajectory of Lucy took it within of Dinkinesh, but a series of planned trajectory correction maneuvers from May to September 2023 allowed Lucy to approach much closer.Dinkinesh was Lucys first and smallest asteroid flyby during its mission, and is the smallest main-belt asteroid explored by spacecraft yet. The Dinkinesh flyby served to test Lucys autonomous tracking capabilities before it will apply them to its main science targets, the Jupiter trojans. Lucy took its first images of Dinkinesh on 3–5 September 2023, when the asteroid was away from the spacecraft. The spacecraft continued imaging Dinkinesh from afar to aid its optical navigation over the days before the flyby. Because Dinkinesh is very small, Lucy did not resolve surface detail on Dinkinesh until the day of the flyby. At closest approach, Lucy was moving relative to Dinkinesh and it was expected to take 2 meters/pixel resolution images of the asteroid with the panchromatic L'LORRI imager, 15 m/pixel color images with the L'Ralph imager, and 24 m/pixel near-infrared spectra and thermal measurements with the L'TES spectrometer. After the flyby, Lucys L'LORRI instrument continued observing Dinkinesh for four days to measure the asteroid's light curve.
Satellite
During its flyby of Dinkinesh, the Lucy spacecraft discovered that the asteroid has a contact binary natural satellite or moon consisting of two conjoined lobes each around in diameter. The moon of Dinkinesh has been named Selam, after the eponymous fossil remains of a three-year-old Australopithecus afarensis female hominin found in Dikika, Ethiopia.Together, Dinkinesh and Selam form a binary asteroid system. Dinkinesh is the second binary main-belt asteroid explored by spacecraft, after 243 Ida by Galileo in 1993. The Dinkinesh binary system resembles the 65803 Didymos near-Earth asteroid binary system in size and composition, but differs in location from the Sun, which allows scientists to compare the nature of binary asteroids in different environments. In the weeks prior to the flyby, the Lucy spacecraft found that Dinkinesh's brightness did not vary as predicted, which provided the first hints of Dinkinesh's binary nature. Images of Selam taken after Lucys approach revealed that it is a contact binary with two lobes attached to each other. While contact binary asteroids are common in the Solar System, Selam is the first known example of a contact binary satellite of an asteroid.
Physical characteristics
Geology
Geological features on Dinkinesh are formally named after words for 'wonderful,' 'marvelous,' or 'beautiful' in the languages of the world. This naming theme was introduced by the International Astronomical Union, which announced the first approved names for Selam's features on 20 December 2024.The surfaces of Dinkinesh and Selam are covered with boulders and craters. The outline of Dinkinesh's shape is not smooth, which suggests that the asteroid is relatively old. Dinkinesh bears an equatorial ridge that has been named Fab Dorsum, which suggests that the asteroid has experienced mass shedding in the past. Dinkinesh's equatorial ridge also has a secondary ridge that branches off it. Dinkinesh's shape resembles the near-Earth asteroids 101955 Bennu and 162173 Ryugu, which are known to have rubble pile interior structures consisting of rocks and dust loosely held by gravity. Because of this similarity, Dinkinesh is thought to likely have a rubble pile structure as well.
| Feature | Center Coordinates | Description | Named after | Name approved (Date |
| Bella Dorsum | 24.40°N, 311.1°W | Elliptical ridge with northern and southern arcs | Italian word for "beautiful" | 2025-12-20 |
| Fab Dorsum | 0°N | Prominent equatorial ridge | English word derived from "fabulous" | 2025-12-20 |
| Indah Fossa | -8.52°N, 4.31°W | Long, narrow trough that appears to postdate other features | Indonesian word for "beautiful" | 2025-12-20 |
| Sumak Fossa | 0.0°N, 354.0°W | Large trough | Kichwa (Ecuadorian Quechua) word for "beautiful" | 2025-12-20 |
| Totoka Saxum | 2.3°N, 356.9°W | Boulder used to define the prime meridian | Fijian word for "beautiful" | 2025-12-20 |