225 Henrietta is a very large outer main-belt asteroid. It was discovered by Austrian astronomer Johann Palisa on April 19, 1882, in Vienna and named after Henrietta, wife of astronomer Pierre J. C. Janssen. The asteroid is orbiting at a distance of from the Sun with a period of and an eccentricity (ovalness) of 0.26. The orbital plane is inclined at an angle of 20.9° to the plane of the ecliptic. 225 Henrietta belongs to Cybele group of asteroids and is probably in a 4:7 orbital resonance with the planet Jupiter. This is classified as a C-type asteroid and is probably composed of primitive carbonaceous material. It has very dark surface, with an albedo of 0.040. Photometric measurements made from the Oakley Southern Sky Observatory during 2012 gave a light curve with a period of and a variation in brightness of in magnitude. This is consistent with a synodic rotation period of determined in 2000. In 2001, the asteroid was detected by radar from the Arecibo Observatory at a distance of 1.58 AU. The resulting data yielded an effective diameter of . References External links The Asteroid Orbital Elements Database Minor Planet Discovery Circumstances Asteroid Lightcurve Data File F-type asteroids (Tholen) Cybele asteroids Henrietta Henrietta 18820419