11409 Horkheimer

11409 Horkheimer, provisional designation 1999 FD₉, is a Themistian asteroid from the outer regions of the asteroid belt, approximately 15 kilometers (9.3 miles) in diameter. It was discovered on 19 March 1999, by astronomers of the Lowell Observatory Near-Earth Object Search at Anderson Mesa Station near Flagstaff, Arizona. The likely C-type asteroid was named for American science communicator Jack Horkheimer.^[1]

11409 Horkheimer

Discovery[1]
Discovered by	LONEOS
Discovery site	Anderson Mesa Stn.
Discovery date	19 March 1999
Designations
MPC designation	(11409) Horkheimer
Named after	Jack Horkheimer[1] (American science communicator)
Alternative designations	1999 FD9 · 1988 HY 1990 RH15
Minor planet category	main-belt[1][2] · (outer) Themis[3]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	29.11 yr (10,632 d)
Aphelion	3.5587 AU
Perihelion	2.8167 AU
Semi-major axis	3.1877 AU
Eccentricity	0.1164
Orbital period (sidereal)	5.69 yr (2,079 d)
Mean anomaly	109.84°
Mean motion	0° 10m 23.52s / day
Inclination	2.2984°
Longitude of ascending node	115.92°
Argument of perihelion	74.973°
Physical characteristics
Mean diameter	15.355±0.100 km[4]
Geometric albedo	0.053±0.005[4]
Spectral type	C (Themis family)
Absolute magnitude (H)	12.8[1][2]

Orbit and classification

Horkheimer is a core member of the Themis family (602),^[3] a very large family of carbonaceous asteroids, named after 24 Themis.^[5] It orbits the Sun in the outer asteroid belt at a distance of 2.8–3.6 AU once every 5 years and 8 months (2,079 days; semi-major axis of 3.19 AU). Its orbit has an eccentricity of 0.12 and an inclination of 2° with respect to the ecliptic.^[2] The body's observation arc begins with its first observation as 1988 HY at the Leoncito Astronomical Complex in April 1988, or 11 years prior to its official discovery observation at Anderson Mesa.^[1]

Physical characteristics

Horkheimer has an absolute magnitude of 12.8.^[1][2] While its spectral type has not been determined, it is likely a carbonaceous C-type asteroid, typical for members of the Themis family.^[5]: 23 As of 2018, no rotational lightcurve has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.^[2]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Horkheimer measures 15.355 kilometers in diameter and its surface has an albedo of 0.053, typical for carbonaceous asteroids.^[4]

Naming

This minor planet was named after Jack F. Horkheimer (1938–2010), director of the Planetarium at the former Miami Science Museum, who was the creator and host of the television program Jack Horkheimer: Star Gazer. The official naming citation was published by the Minor Planet Center on 9 January 2001 (M.P.C. 41938).^[6]