101 Helena

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101 Helena
Orbita asteroida 101.png
Orbital diagram
Discovery
Discovered by James Craig Watson
Discovery date15 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
Dimensions65.84±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

    Helena (minor planet designation: 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]

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    References

    1. Noah Webster (1884) A Practical Dictionary of the English Language
    2. 1 2 3 4 5 Yeomans, Donald K., "101 Helena", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, archived from the original on 24 September 2014, retrieved 12 May 2016.
    3. 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, archived from the original (PDF) on 17 March 2014, retrieved 22 March 2013. See appendix A.
    4. "Numbered Minor Planets 1–5000", Discovery Circumstances, IAU Minor Planet center, retrieved 7 April 2013.
    5. 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, vol. 186, no. 1, pp. 126–151, Bibcode:2007Icar..186..126M, doi:10.1016/j.icarus.2006.08.018.