101 Helena

Not to be confused with Helene (moon).

101 Helena
Orbital diagram
Discovery
Discovered byJames 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 arc145.07 yr (52986 d)
Aphelion2.94606 AU (440.724 Gm)
Perihelion2.22353 AU (332.635 Gm)
2.58480 AU (386.681 Gm)
Eccentricity0.13977
4.16 yr (1517.9 d)
18.44 km/s
236.265°
0° 14m 13.823s / day
Inclination10.1976°
343.419°
348.030°
Earth MOID1.21369 AU (181.565 Gm)
Jupiter MOID2.4117 AU (360.79 Gm)
TJupiter3.387
Physical characteristics
Dimensions65.84±1.3 km[2]
Mass3.0×1017 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]

References

  1. ^ Noah Webster (1884) A Practical Dictionary of the English Language
  2. ^ a b c d e 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. ^ a b 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, 186 (1): 126–151, Bibcode:2007Icar..186..126M, doi:10.1016/j.icarus.2006.08.018.
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