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Discovery
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| Discovered by | Max Wolf |
| Discovery date | February 6, 1916 |
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Designations
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| Alternate name(s) | 1916 YW |
| Minor planet category |
Main belt (Eunomia family) |
| Epoch 8 August 2005 (JD 2453600.5) | |
| Aphelion | 456.6 Gm (3.053 AU) |
| Perihelion | 317.9 Gm (2.125 AU) |
| Semi-major axis | 387.3 Gm (2.589 AU) |
| Eccentricity | 0.179 |
| Orbital period | 1521.586 d (4.20 a) |
| Average orbital speed | 18.36 km/s |
| Mean anomaly | 224.421° |
| Inclination | 11.345° |
| Longitude of ascending node | 125.701° |
| Argument of perihelion | 284.937° |
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Physical characteristics
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| Dimensions | 22 km[1] |
| Mass | ~1.5×1016 kg (estimate) |
| Mean density | ~2.7 g/cm³ (estimate)[3] |
| Equatorial surface gravity | ~0.008 m/s² (estimate) |
| Escape velocity | ~0.013 km/s (estimate) |
| Rotation period | 0.440 d [2] |
| Albedo | 0.174 |
| Temperature | ~169 K max: 264K (-9° C) |
| Spectral type | S-type asteroid |
| Absolute magnitude (H) | 10.80 |
817 Annika is a mid-sized Eunomian asteroid.
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