Heracles orbits the Sun in theinner main-belt at a distance of 0.4–3.2 AU once every 2 years and 6 months (907 days). Its orbit has aneccentricity of 0.77 and aninclination of 9° with respect to theecliptic.[1] The firstprecovery was taken at Palomar during theDigitized Sky Survey in 1953, extending the body'sobservation arc by 38 years prior to its official discovery observation.[3]
A large number of rotationallightcurves of Heracles were obtained from photometric observations between 2006 and 2016. Lightcurve data gives arotation period between 2.7051 and 2.7065 hours with a brightness variation of 0.05 to 0.20magnitude (U=3/3/3/3/3-).[5][11][15][16][a]
According to the surveys carried out by theSpitzer Space Telescope, the JapaneseAkari satellite, and NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission, the asteroid measures between 3.26 and 4.843 kilometers in diameter, and its surface has analbedo between 0.20 and 0.24.[8][9][10][13] TheCollaborative Asteroid Lightcurve Link adopts the results fromPetr Pravec's revised WISE data, that is, an albedo of 0.1481 and a diameter of 4.83 kilometers with anabsolute magnitude of 14.27.[11][12]
On 12 July 2012, it was announced that Heracles is an assumed synchronousbinary asteroid with aminor-planet moon orbiting its primary in aretrograde motion approximately every 16 hours. The companion was discovered in December 2011, by a team of astronomers using radar observations fromArecibo Observatory in Puerto Rico, following months of intensive photometric lightcurve observations(see above).
A longerorbital period of 40–57 hours cannot be excluded, which would then no longer be a synchronous system. Estimated diameters for Heracles and its moon are3.6±1.2 and0.6±0.3 kilometer, respectively.[6][7][11]
Follow-up observations in 2016 confirmed an orbital period of 17 hours for the asteroid moon.[25]
^abWarner (2017c):lightcurve plot of (5143) Heracles, with a rotation period2.704±0.002 hours and a brightness amplitude of0.15 mag (Quality Code of 2; 133 points). Observations from 12 to 17 September 2016, at CS3-Palmer Divide Station. Summary figures atCollaborative Asteroid Lightcurve Link (CALL)
^abcdefgPilcher, Frederick; Briggs, John W.; Franco, Lorenzo; Inasaridze, Raguli Ya.; Krugly, Yurij N.; Molotiv, Igor E.; et al. (July 2012). "Rotation Period Determination for 5143 Heracles".The Minor Planet Bulletin.39 (3):148–151.Bibcode:2012MPBu...39..148P.ISSN1052-8091.
^abcdPravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations".Icarus.221 (1):365–387.Bibcode:2012Icar..221..365P.doi:10.1016/j.icarus.2012.07.026.
^abcPolishook, David (July 2012). "Lightcurves and Spin Periods of Near-Earth Asteroids, The Wise Observatory, 2005 - 2010".The Minor Planet Bulletin.39 (3):187–192.Bibcode:2012MPBu...39..187P.ISSN1052-8091.
^Linder, Tyler R.; Sampson, Ryan; Holmes, Robert (January 2013). "Astronomical Research Institute Photometric Results".The Minor Planet Bulletin.40 (1):4–6.Bibcode:2013MPBu...40....4L.ISSN1052-8091.
