# 806 Gyldenia
**806 Gyldenia** (provisional designation 1915 WX) is a carbonaceous asteroid in the outer region of the main asteroid belt, roughly 63 to 83 kilometers across depending on the measurement, with a very dark surface and a slow rotation period of about 16.85 hours. It was discovered on 18 April 1915 by the German astronomer [Max Wolf](https://www.edgepedia.org/max-wolf) at Heidelberg Observatory.[1](https://clever-geek.imtqy.com/articles/1389730/index.html)
| Key fact | Detail |
|---|---|
| Discovery | 18 April 1915, Heidelberg, by Max Wolf; provisional designation 1915 WX[1](https://clever-geek.imtqy.com/articles/1389730/index.html) |
| Orbit | Semi-major axis 3.204 AU, eccentricity 0.0812, inclination 14.22°, orbital period 2,100 days (5.75 years)[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he) |
| Diameter | Published estimates include 62.6 km[3](https://www.bahnsen.de/jens/astro/aster/h-gurt500-1000.htm) and 83.10 km[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he); the DAMIT shape model gives a calibrated 55 ± 4 km[4](https://damit.cuni.cz/asteroid_models/view/3880) |
| Albedo | About 0.023, a very dark surface[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he) |
| Rotation | About 16.85 hours; the DAMIT model lists P = 16.857 h[4](https://damit.cuni.cz/asteroid_models/view/3880) |
| Spin axis | Ecliptic pole coordinates λ = 235°, β = 42° in DAMIT model 3880[4](https://damit.cuni.cz/asteroid_models/view/3880) |
| Observational record | 6,777 observations used for orbit determination, dating back to the 1915 discovery[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he) |
## Orbit and classification
Gyldenia orbits the Sun in the outer main belt between Mars and Jupiter, on a nearly circular path with eccentricity 0.0812 tilted 14.22° to the ecliptic. It comes as close as 2.94 AU and recedes to 3.46 AU, completing one revolution every 2,100 days at an average orbital speed of 16.60 km/s.[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he) A German-language asteroid catalog lists a semi-major axis of 3.213 AU and a diameter of 62.6 km for the object.[3](https://www.bahnsen.de/jens/astro/aster/h-gurt500-1000.htm)
The asteroid is classified as an outer main-belt object and is not a near-Earth object. Its orbit stays at least 1.98 AU from [Earth's orbit](https://www.edgepedia.org/earths-orbit) at the closest point, and orbital simulations by NASA JPL's Center for Near-Earth Object Studies show no close approaches to Earth; it is also not rated a viable target for human exploration in the NHATS study.[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he)
## Size and surface
Diameter estimates for Gyldenia differ by method. The value of 83.10 km comes from one survey determination and would make the asteroid larger than 99% of known asteroids, comparable in size to the U.S. state of Delaware.[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he) Smaller values near 62.6 km appear in other compilations.[3](https://www.bahnsen.de/jens/astro/aster/h-gurt500-1000.htm) The shape model in the Database of Asteroid Models from Inversion Techniques (DAMIT), calibrated against size data, gives a volume-equivalent diameter of 55 ± 4 km.[4](https://damit.cuni.cz/asteroid_models/view/3880)
All determinations agree that the surface is very dark, with a geometric albedo of about 0.023, meaning the body reflects only a few percent of the sunlight hitting it. Such low albedos are typical of carbonaceous (C-type) asteroids in the outer belt.[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he)
## Rotation and shape model
Gyldenia is a slow rotator. Photometric campaigns have produced composite light curves from observing seasons in 2013, 2015, 2016, 2018, 2020, and 2021, with derived [synodic periods](https://www.edgepedia.org/synodic-period) clustered around 16.85 hours (for example 16.863 h in 2015, 16.857 h in 2018, and 16.853 h in 2021).[5](https://www.aanda.org/articles/aa/pdf/2023/11/aa46191-23.pdf) The DAMIT entry for the asteroid lists a sidereal period of 16.857 hours.[4](https://damit.cuni.cz/asteroid_models/view/3880)
The DAMIT shape model 3880, created in 2019 and last modified in October 2023, gives a spin-axis orientation of ecliptic longitude λ = 235° and latitude β = 42°, carries a quality flag of 3.5, and is a convex (non-nonconvex) model fitted with a Lambert-like light scattering law.[4](https://damit.cuni.cz/asteroid_models/view/3880) A 2023 study that scaled slowly rotating asteroids using stellar occultations reports that the spin solution for Gyldenia is constrained to within a few degrees.[6](https://www.researchgate.net/publication/374311646_Scaling_slowly_rotating_asteroids_with_stellar_occultations)
## Observational history
The discovery observation of 18 April 1915 is the earliest data point in the object's record, and the [Minor Planet Center](https://www.edgepedia.org/minor-planet-center)'s orbit solution rests on 6,777 observations, with the most recent official observation recorded on 21 April 2023.[2](https://www.spacereference.org/asteroid/806-gyldenia-a915-he) The DAMIT database holds dozens of individual light curves of Gyldenia, numbered 30745 through 30807, contributed to the shape-modeling effort.[7](https://damit.cuni.cz/projects/damit/asteroids/view/2202)
## References
1. [Asteroid List (801–900)](https://clever-geek.imtqy.com/articles/1389730/index.html)
2. [Asteroid Gyldenia, Space Reference](https://www.spacereference.org/asteroid/806-gyldenia-a915-he)
3. [Asteroiden des Hauptgürtels (500–1000)](https://www.bahnsen.de/jens/astro/aster/h-gurt500-1000.htm)
4. [(806) Gyldenia – Model 3880, DAMIT](https://damit.cuni.cz/asteroid_models/view/3880)
5. [Marciniak, A., et al. (2023). Scaling slowly rotating asteroids with stellar occultations. A&A, 679, A60](https://www.aanda.org/articles/aa/pdf/2023/11/aa46191-23.pdf)
6. [Scaling slowly rotating asteroids with stellar occultations, ResearchGate](https://www.researchgate.net/publication/374311646_Scaling_slowly_rotating_asteroids_with_stellar_occultations)
7. [Asteroid (806) Gyldenia, DAMIT](https://damit.cuni.cz/projects/damit/asteroids/view/2202)
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*Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Main-belt asteroids and numbered minor planets › Outer-belt asteroids › Asteroids named after people*
*Initially written Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license