9950 ESA, provisional designation , is an eccentric

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

and elongated

near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...

of the

Amor group Amor Group was Scotland's largest independent business technology company before being acquired by Lockheed Martin in September 2013. The business was formed after a £28 million management buyout of Glasgow based Real Time Engineering Ltd. an ...

, approximately 1.7 kilometers in diameter. It was discovered on 8 November 1990, by French astronomer

Christian Pollas Christian Pollas (b. 1947) is a French astronomer, known for the discovery and observation of minor planets and supernovae. Pollas is credited by the Minor Planet Center with the discovery of 26 asteroids, some co-discovered with Eric W. Elst, ...

at the

Centre de recherches en géodynamique et astrométrie The CERGA Observatory (, ; List of observatory codes, obs. code: IAU code#010, 010) was a scientific department and astronomical station of the Côte d'Azur Observatory in southern France, where several asteroids were discovered during 1984–1993 ...

(Cerga) at Caussols in southeastern France. It was named for the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

(ESA).

Orbit and classification

''ESA'' is an

Amor asteroid The Amor asteroids are a group of near-Earth asteroids named after the archetype object 1221 Amor . The orbital perihelion of these objects is close to, but greater than, the orbital aphelion of Earth (i.e., the objects do not cross Earth's orbit ...

– a subgroup of near-Earth asteroids that approach the orbit of Earth from beyond, but do not cross it. It orbits the Sun at a distance of 1.1–3.7 AU once every 3 years and 10 months (1,390 days). 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 0.53 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 15 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. 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 ...

begins with its official discovery observation at Caussols in November 1990.

Close approaches

''ESA'' has an Earth

minimum orbit intersection distance Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits o ...

of , which corresponds to 109.3 lunar distances. It approached the Earth at 0.393 AU on 18 October 1990, three weeks prior to its discovery, and made two more close approaches in August and September 2013, respectively. Its next close encounter with Earth will be in October 2032, at distance of . The eccentric asteroid is also a

Mars-crosser A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and . Many databases, for i ...

. In March 1987, it approached the Red Planet at .

Physical characteristics

''ESA'' is an assumed stony

S-type asteroid S-type (stony-type or silicaceous-type) asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are ...

Rotation period

In 2013, three rotational

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

s of ''ESA'' were obtained from photometric observations by the EURONEAR Lightcurve Survey and by American astronomers Brian Warner and

Robert Stephens Sir Robert Graham Stephens (14 July 193112 November 1995) was an English actor in the early years of Britain's Royal National Theatre. Early life Stephens was born in Shirehampton, Bristol, in 1931, the eldest of three children of shipyard ...

at the Center for Solar System Studies (). Lightcurve analysis gave a

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

between 6.707 and 6.712 hours with a brightness variation of 0.44 to 0.89

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 ...

(). A high brightness amplitude typically indicates that the body's shape is irregular and elongated, rather than spherical.

Diameter and albedo

In the early 1990s,

David Tholen David James Tholen (born 1955) is an American astronomer at the Institute for Astronomy of the University of Hawaiʻi. He holds a 1978 B.S. from the University of Kansas, a 1984 PhD from the University of Arizona, and specializes in planetary ...

at the Institute for Astronomy of the University of Hawaii estimated a diameter of 3 kilometers for ''ESA''. The ''Collaborative Asteroid Lightcurve Link'' assumes a standard

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

for stony asteroids of 0.20 and calculates a diameter of 1.71 kilometers based on an absolute magnitude of 16.2.

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 ''minor ...

was named after the

(ESA), which formed in 1974. The name was suggested by French astronomer Jean Louis Heudier, after whom the asteroid 4602 Heudier was named. The official naming citation was published by the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Funct ...

on 15 December 2005 ().

Notes

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend * * * {{DEFAULTSORT:ESA 009950 Discoveries by Christian Pollas Named minor planets 19901108