52246 Donaldjohanson, provisional designation , is a carbonaceous Erigonian asteroid from the inner regions of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, c ...

, approximately in diameter. It was discovered on 2 March 1981, by American astronomer

Schelte Bus Schelte John "Bobby" Bus (born 1956) is an American astronomer and discoverer of minor planets at the Institute for Astronomy of the University of Hawaii and deputy director of NASA's Infrared Telescope Facility (IRTF) at the Mauna Kea Observat ...

at the Siding Spring Observatory in Australia. The

C-type asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

is a target of the ''Lucy'' mission and was aptly named after American paleoanthropologist

Donald Johanson Donald Carl Johanson (born June 28, 1943) is an American paleoanthropologist. He is known for discovering, with Yves Coppens and Maurice Taieb, the fossil of a female hominin australopithecine known as "Lucy" in the Afar Triangle region of Hada ...

Orbit and classification

Animation of Lucy's trajectory around Sun

Donaldjohanson is a member of the

Erigone family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. An ...

(), a large carbonaceous asteroid family of nearly 2,000 known members, which is named after its

parent body In meteoritics, a parent body is the celestial body from which originates a meteorite or a class of meteorites. Identification The easiest way to correlate a meteorite with a parent body is when the parent body still exists. This is the case fo ...

163 Erigone. It is a relatively old family that was created approximately 130 million years ago. It orbits the Sun in the

inner Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

asteroid belt at a distance of 1.9–2.8 AU once every 3 years and 8 months (1,345 days; semi-major axis of 2.38 AU). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.19 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 4 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

. A first precovery was taken at the discovering observatory in February 1981, extending the body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

by 2 weeks prior to its official discovery observation.

''Lucy'' mission target

Donaldjohanson is planned to be visited by the ''Lucy'' spacecraft that was launched on 16 October 2021. The flyby is scheduled for 20 April 2025, and will approach the asteroid to a distance of at a velocity of per second.

Physical characteristics

Donaldjohanson has been characterized as a carbonaceous

, in-line with the C and X overall

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

for Erigonian asteroids. It has an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

of 15.5.

Lightcurve

Photometric observations of Donaldjohanson in August 2020 revealed that it is a slow rotator with an exceptionally high

lightcurve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular freq ...

amplitude of 1.7

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

. The lightcurve suggests that Donaldjohanson must either be highly elongated in shape, or possibly a synchronous

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

. Extensive photometric observations by the two

TRAPPIST The Trappists, officially known as the Order of Cistercians of the Strict Observance ( la, Ordo Cisterciensis Strictioris Observantiae, abbreviated as OCSO) and originally named the Order of Reformed Cistercians of Our Lady of La Trappe, are a ...

telescopes from November 2020 to February 2021 determined the rotation period of Donaldjohanson to be approximately 252 hours.

Diameter and albedo

According to the survey carried out by NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 201 ...

with its subsequent

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 201 ...

mission, Donaldjohanson measures 3.895 kilometers in diameter and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

of 0.103.

Naming

This

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''mino ...

is planned to be visited by the ''

Lucy Lucy is an English feminine given name derived from the Latin masculine given name Lucius with the meaning ''as of light'' (''born at dawn or daylight'', maybe also ''shiny'', or ''of light complexion''). Alternative spellings are Luci, Luce, Lu ...

'' spacecraft, which would observe it en route to its main target of several

Jupiter trojans The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to Jupiter, each trojan librates around one of Jupiter's stable Lagrange poin ...

. The Lucy probe is named after the "Lucy" hominid fossil, while Donaldjohanson is named for that fossil's co-discoverer

(born 1943), an American paleoanthropologist. The approved naming citation was published by the Minor Planet Center on 25 December 2015 ().

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Donaldjohanson 052246 Discoveries by Schelte J. Bus Named minor planets Slow rotating minor planets 052246 19810302