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 | |
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.
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]
JPL
was invoked but never defined (see the help page).DeMeo2011
was invoked but never defined (see the help page).IAU_MPC
was invoked but never defined (see the help page).Icarus186
was invoked but never defined (see the help page).