In August 2011, a rotational lightcurve of Prothoon was obtained from photometric observations by Robert Stephens at the Goat Mountain Astronomical Research Station (G79) in California. Lightcurve analysis gave a rotation period of 15.82 hours with a brightness amplitude of 0.20 magnitude (U=3-).[3][9]
Diameter and albedo
According to the surveys carried out by the Japanese Akari satellite, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, and the Infrared Astronomical Satellite IRAS, Prothoon measures between 62.41 and 64.31 kilometers in diameter and its surface has an albedo between 0.039 and 0.052.[6][7][8]
The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0467 and a diameter of 64.41 kilometers based on an absolute magnitude of 9.9.[3]
100+ largest Jupiter trojans
Largest Jupiter Trojans by survey(A) (mean-diameter in kilometers; YoD: Year of Discovery)
Note: missing data was completed with figures from the JPL SBDB (query) and from the LCDB (query form) for the WISE/NEOWISE and SIMPS catalogs, respectively. These figures are given in italics. Also, listing is incomplete above #100.
^ abcdTedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System – IRAS-A-FPA-3-RDR-IMPS-V6.0. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 15 June 2018.
^ abFrench, Linda M.; Stephens, Robert D.; Coley, Daniel R.; Megna, Ralph; Wasserman, Lawrence H. (July 2012). "Photometry of 17 Jovian Trojan Asteroids". The Minor Planet Bulletin. 39 (3): 183–187. Bibcode:2012MPBu...39..183F. ISSN1052-8091.
^Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. S2CID53493339.