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Discovery
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| Discovered by | James Craig Watson |
| Discovery date | August 15, 1868 |
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Designations
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| Named after | Helen of Troy |
| Alternate name(s) | |
| Minor planet category |
Main belt |
| Epoch December 31, 2006 (JD 2454100.5) | |
| Aphelion | 441.092 Gm (2.949 AU) |
| Perihelion | 331.683 Gm (2.217 AU) |
| Semi-major axis | 386.387 Gm (2.583 AU) |
| Eccentricity | 0.142 |
| Orbital period | 1516.159 d (4.15 a) |
| Average orbital speed | 18.44 km/s |
| Mean anomaly | 125.599° |
| Inclination | 10.199° |
| Longitude of ascending node | 343.471° |
| Argument of perihelion | 347.818° |
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Physical characteristics
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| Dimensions | 65.8 km |
| Mass | 3.0×1017 kg |
| Mean density | 2.0 g/cm³ |
| Equatorial surface gravity | 0.0184 m/s² |
| Escape velocity | 0.0348 km/s |
| Rotation period | ? d |
| Albedo | ? |
| Temperature | ~173 K |
| Spectral type | S |
| Absolute magnitude (H) | 8.33 |
101 Helena is a fairly small, rocky main-belt asteroid. It was discovered by J. C. Watson on August 15, 1868. It is named after Helen of Troy in Greek mythology.
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