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(15692) 1984 RA
(15692) 1984 RA (provisional designation 1984 RA) is a Hungaria asteroid from the innermost regions of the asteroid belt, approximately 2 kilometers (1.2 miles) in diameter. It was discovered on 1 September 1984, by Italian astronomer Maria Barucci at the Palomar Observatory in California, United States.[1] The presumed E-type asteroid has a longer-than average rotation period of 37.4 hours and possibly an elongated shape.[3] Orbit and classification1984 RA is a bright core member of the Hungaria family (003),[4] a large family of three thousand asteroids located within the dynamical group with the same name.[1][3] Hungarias form the innermost dense concentration of asteroids in the Solar System; they are inside the asteroid belt's core region, sometimes considered a completely independent population.[9] The asteroid orbits the Sun in the innermost asteroid belt at a distance of 1.7–2.1 AU once every 2 years and 8 months (977 days; semi-major axis of 1.93 AU). Its orbit has an eccentricity of 0.10 and an inclination of 23° with respect to the ecliptic.[2] The body's observation arc begins with a precovery found in the Digitized Sky Survey and taken at the Siding Spring Observatory in November 1977, almost 7 years prior to its official discovery observation at Palomar.[1] Physical characteristics1984 RA is an assumed E-type asteroid, known for their high albedos, typically around 0.4.[3] Rotation periodIn July 2013, a rotational lightcurve of this asteroid was obtained from photometric observations by American astronomer Brian Warner at the Palmer Divide Station (U82) in California. Lightcurve analysis gave a long rotation period of 37.44 hours with a brightness amplitude of 0.66 magnitude, indicative of an elongated shape (U=2).[7][a] While not being a slow rotator, 1984 RA has a significantly longer period than most asteroids, which rotate once every 2 to 20 hours around their axis. Diameter and albedoAccording to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, this asteroid measures 1.728 kilometers in diameter and its surface has an exceptionally high albedo of 0.78.[5][6] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.30 – a compromise value between the E- (0.40) and S-type (0.20) members of the Hungaria family and group, respectively – and calculates a diameter of 2.43 kilometers based on an absolute magnitude of 15.0.[3] Numbering and namingThis minor planet was numbered by the Minor Planet Center on 26 July 2000 (M.P.C. 40991).[10] As of 2018, it has not been named.[1] Notes
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