101 Helena

101 Helena
Discovery
Discovered by James Craig Watson
Discovery date 15 August 1868
Designations
MPC designation (101) Helena
Named after
 Helen of Troy
 
Main belt
Orbital characteristics[1]
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)
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)
Jupiter Tisserand parameter 3.387
Physical characteristics
Dimensions 65.84±1.3 km[1]
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)[1]
0.1898±0.008[1]
Temperature ~173 K
S[2]
8.33

    101 Helena is a rocky main-belt asteroid. It was discovered by Canadian-American astronomer J. C. Watson on August 15, 1868,[3] and was named after Helen of Troy in Greek mythology. 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 diameter estimated from IRAS infrared measurements is 66 km. It is classified as an S-type asteroid in the Tholen system.[2][4]

    References

    1. 1 2 3 4 Yeomans, Donald K., "101 Helena", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 12 May 2016.
    2. 1 2 DeMeo, Francesca E.; et al. (2011), "An extension of the Bus asteroid taxonomy into the near-infrared" (PDF), Icarus, 202 (1): 160–180, Bibcode:2009Icar..202..160D, doi:10.1016/j.icarus.2009.02.005, retrieved 2013-03-22. See appendix A.
    3. ↑ "Numbered Minor Planets 1–5000", Discovery Circumstances, IAU Minor Planet center, retrieved 2013-04-07.
    4. ↑ Magri, Christopher; Nolan, Michael C.; Ostro, Steven J.; Giorgini, Jon D. (January 2007), "A radar survey of main-belt asteroids: Arecibo observations of 55 objects during 1999 2003", Icarus, 186 (1), pp. 126–151, Bibcode:2007Icar..186..126M, doi:10.1016/j.icarus.2006.08.018.


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