101 Helena
Main-belt asteroid
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101 Helena is a large, rocky main-belt asteroid. It was discovered by Canadian-American astronomer J. C. Watson on August 15, 1868,[4] and was named after Helen of Troy in Greek mythology.
Orbital diagram | |
| Discovery | |
|---|---|
| Discovered by | James Craig Watson |
| Discovery date | 15 August 1868 |
| Designations | |
| (101) Helena | |
| Pronunciation | /ˈhɛlənə/[1] |
Named after | Helen of Troy |
| A868 PA | |
| Main belt | |
| Orbital characteristics[2] | |
| Epoch 31 July 2016 (JD 2457600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 145.07 yr (52986 d) |
| Aphelion | 2.94606 AU (440.724 Gm) |
| Perihelion | 2.22353 AU (332.635 Gm) |
| 2.58480 AU (386.681 Gm) | |
| Eccentricity | 0.13977 |
| 4.16 yr (1517.9 d) | |
Average orbital speed | 18.44 km/s |
| 236.265° | |
| 0° 14m 13.823s / day | |
| Inclination | 10.1976° |
| 343.419° | |
| 348.030° | |
| Earth MOID | 1.21369 AU (181.565 Gm) |
| Jupiter MOID | 2.4117 AU (360.79 Gm) |
| TJupiter | 3.387 |
| Physical characteristics | |
| Dimensions | 65.84±1.3 km[2] |
| Mass | 3.0×1017 kg |
Mean density | 2.0 g/cm3 |
Equatorial surface gravity | 0.0184 m/s2 |
Equatorial escape velocity | 0.0348 km/s |
| 23.080 h (0.9617 d)[2] | |
| 0.1898±0.008[2] | |
| Temperature | ~173 K |
| S[3] | |
| 8.33 | |
This object is orbiting the Sun with a period of 4.16 years and an eccentricity of 0.14. Its orbital plane is inclined by 10.2° to the plane of the ecliptic. Radar observations were made of this object on Oct 7 and 19, 2001 from the Arecibo Observatory. Analysis of the data gave an estimated ellipsoidal diameter of 71×63×63 ± 16% km. The mean diameter estimated from IRAS infrared measurements is 66 km, in agreement with the radar findings. It is classified as an S-type asteroid in the Tholen system,[3][5] suggesting a predominantly silicate composition. 101 Helena is spinning on its axis with a period of 23 hours.[2]
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