It was discovered on 7 January 1976, at the Palomar Observatory by American astronomer Eleanor Helin,[2] who was the principal scientist for the NEAT project until her retirement in 2002. The S-type asteroid measures approximately 900 meters in diameter, has a longer-than average rotation period of 44.77 hours, and approaches the orbit Earth to 44.1 lunar distances.
Orbit and classification
Aten orbits the Sun at a distance of 0.8–1.1 AU once every 11 months (347 days). Its orbit has an eccentricity of 0.18 and an inclination of 19° with respect to the ecliptic.[1] A first precovery was taken at the discovering observatory in December 1955, extending the body's observation arc by more than 20 years prior to its official discovery observation.[2]
Namesake of the Aten group
Aten was the first asteroid found to have a semi-major orbital axis of less than one astronomical unit and a period of less than one year.[3] A new category of asteroids was thus created, the Atens. As of 2017, the group consists of more than 1,200 numbered members. Other groups of near-Earth objects (NEOs) are the Apollo and Amor asteroids, which are both significantly larger than the Atens, while the Atira asteroids form the smallest NEO-group by far.[13]
In the 1990s, Italian astronomer Stefano Mottola obtained a rotational lightcurve of Aten during the EUNEASO survey at La Silla, which was a European near-Earth object search and follow-up observation program to determine additional physical parameters. Lightcurve analysis gave a longer-than average rotation period of 40.77 hours with a brightness variation of 0.26 magnitude (U=2).[9] No additional lightcurves have been obtained since.[12]
Diameter and albedo
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Aten measures between 700 and 830 meters in diameter and its surface has a high albedo between 0.39 and 0.52.[4][5]
in 1994, Tom Gehrels published a diameter of 1.1 kilometers and an albedo of 0.26 in his book Hazards Due to Comets and Asteroids.[1][7] The Warm Spitzer NEO survey ("ExploreNEOs") gives a diameter of 1.3 kilometers with an albedo of 0.20.[8]
The Collaborative Asteroid Lightcurve Link agrees with a revised thermal model for asteroid diameters and albedos, and adopts an albedo of 0.28 with a diameter of 0.91 kilometers based on an absolute magnitude of 17.2.[6][12] However, the Minor Planet Center (MPC) classifies Aten as a larger "1+ KM" object.[2]
^ abcMottola, S.; de Angelis, G.; di Martino, M.; Erikson, A.; Harris, A. W.; Hahn, G.; et al. (March 1995). "The EUNEASO Photometric Follow-up Program". Abstracts of the Lunar and Planetary Science Conference. 26: 1003. Bibcode:1995LPI....26.1003M.