636 Erika is a minor planet located in the outer region of the asteroid belt. It is a background (non‑family) asteroid of the main belt and is classified as a dark, carbonaceous object (spectral type C). The asteroid was discovered by the German astronomer Max Wolf at the Heidelberg‑Königstuhl Observatory on 8 March 1907. Its provisional designation at the time of discovery was 1907 AL.
Orbital characteristics (reference epoch J2000.0)
- Semi‑major axis: ≈ 3.15 AU
- Eccentricity: ≈ 0.13
- Orbital period: ≈ 5.59 yr (≈ 2 041 days)
- Inclination to the ecliptic: ≈ 3.5°
- Mean anomaly, argument of perihelion, and longitude of the ascending node are defined in standard orbital element tables for the epoch.
Physical characteristics
- Absolute magnitude (H): ≈ 10.5
- Estimated diameter: ≈ 55–60 km (derived from infrared surveys such as IRAS and NEOWISE)
- Geometric albedo: ≈ 0.05, consistent with a carbon‑rich surface.
Naming
The name “Erika” was assigned to the asteroid shortly after its discovery. The official citation does not provide an explicit reference for the choice of name; consequently, the specific individual or cultural reference intended by the namer remains undocumented in the historical record.
Discovery circumstances
The discovery was part of a prolific series of asteroid observations conducted by Max Wolf, who pioneered the use of astrophotography for the detection of minor planets. The observation was recorded on photographic plates taken at the Heidelberg observatory, and subsequent astrometric measurements confirmed its heliocentric orbit.
Observational history
Since its discovery, 636 Erika has been observed continuously, allowing precise determination of its orbit and physical parameters. Light‑curve analyses have yielded a rotation period of roughly 9.5 hours, though detailed shape modeling remains limited.
References
- Minor Planet Center database, orbital elements for 636 Erika.
- JPL Small‑Body Database Browser, NASA/Jet Propulsion Laboratory.
- IRAS Minor Planet Survey, diameter and albedo data.
Note: All numerical values are presented as approximations derived from publicly available astronomical databases and may be refined by future observations.