| Minorplanet: | yes |
| 11409 Horkheimer | |
| Background: |
|
| Discovered: | 19 March 1999 |
| Mpc Name: | (11409) Horkheimer |
| Alt Names: | 1988 HY |
| Named After: | Jack Horkheimer |
| Epoch: | 23 March 2018 (JD 2458200.5) |
| Uncertainty: | 0 |
| Observation Arc: | 29.11 yr (10,632 d) |
| Perihelion: | 2.8167 AU |
| Semimajor: | 3.1877 AU |
| Eccentricity: | 0.1164 |
| Period: | 5.69 yr (2,079 d) |
| Mean Motion: | / day |
| Inclination: | 2.2984° |
| Asc Node: | 115.92° |
| Arg Peri: | 74.973° |
| Abs Magnitude: | 12.8 |
11409 Horkheimer, provisional designation, is a Themistian asteroid from the outer regions of the asteroid belt, approximately 15km (09miles) 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.
Horkheimer is a core member of the Themis family, a very large family of carbonaceous asteroids, named after 24 Themis. 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. The body's observation arc begins with its first observation as at the Leoncito Astronomical Complex in April 1988, or 11 years prior to its official discovery observation at Anderson Mesa.
Horkheimer has an absolute magnitude of 12.8. While its spectral type has not been determined, it is likely a carbonaceous C-type asteroid, typical for members of the Themis family. As of 2018, no rotational lightcurve has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.
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.
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 .The official naming citation was published by the Minor Planet Center on 9 January 2001 .