101 Helena
{{Short description|Main-belt asteroid}}
{{Distinguish|Helene (moon)}}
{{Use dmy dates|date=October 2019}}
{{Infobox planet
| minorplanet=yes
| background=#D6D6D6
| name=101 Helena
|image= Орбита астероида 101.png
|caption=Orbital diagram
| discoverer=James Craig Watson
| discovered=15 August 1868
| mpc_name=(101) Helena
| alt_names=A868 PA
| pronounced={{IPAc-en|'|h|ɛ|l|ə|n|ə}}Noah Webster (1884) A Practical Dictionary of the English Language
| named_after=Helen of Troy
| mp_category=Main belt
| epoch=31 July 2016 (JD 2457600.5)
| semimajor={{Convert|2.58480|AU|Gm|abbr=on}}
| perihelion={{Convert|2.22353|AU|Gm|abbr=on}}
| aphelion={{Convert|2.94606|AU|Gm|abbr=on|lk=on}}
| eccentricity=0.13977
| inclination=10.1976°
| asc_node=343.419°
| arg_peri=348.030°
| mean_anomaly=236.265°
| avg_speed=18.44 km/s
| dimensions={{val|65.84|1.3|ul=km}}
| mass=3.0{{E|17}} kg
| density=2.0 g/cm3
| surface_grav=0.0184 m/s2
| escape_velocity=0.0348 km/s
| rotation={{Convert|23.080|h|d|abbr=on|lk=on}}
| spectral_type=S
| abs_magnitude=8.33
| single_temperature=~173 K
| mean_motion={{Deg2DMS|0.237173|sup=ms}} / day
| observation_arc=145.07 yr (52986 d)
| uncertainty=0
| moid={{Convert|1.21369|AU|Gm|abbr=on}}
| jupiter_moid={{Convert|2.4117|AU|Gm|abbr=on}}
| tisserand=3.387
}}
101 Helena is a large, rocky main-belt asteroid. It was discovered by Canadian-American astronomer J. C. Watson on August 15, 1868, 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, suggesting a predominantly silicate composition. 101 Helena is spinning on its axis with a period of 23 hours.
References
{{Reflist|refs=
| title = Numbered Minor Planets 1–5000
| work = Discovery Circumstances
| publisher = IAU Minor Planet center
| url = https://www.minorplanetcenter.net/iau/lists/NumberedMPs000001.html
| accessdate= 2013-04-07
| postscript= .
}}
| first1 = Donald K.
| last1 = Yeomans
| title = 101 Helena
| work = JPL Small-Body Database Browser
| publisher = NASA Jet Propulsion Laboratory
| url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=101
| archive-url = https://web.archive.org/web/20140924202533/http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=101
| url-status = dead
| archive-date = 24 September 2014
| accessdate= 12 May 2016
| postscript= .
}}
| first1 = Christopher
| last1 = Magri
| first2 = Michael C.
| last2 = Nolan
| first3 = Steven J.
| last3 = Ostro
| first4 = Jon D.
| last4 = Giorgini
| title = A radar survey of main-belt asteroids: Arecibo observations of 55 objects during 1999 2003
| journal = Icarus
| volume = 186
| issue = 1
| pages = 126–151
|date=January 2007
| doi = 10.1016/j.icarus.2006.08.018
| bibcode = 2007Icar..186..126M
| postscript= .
}}
|first1 = Francesca E.
|last1 = DeMeo
|first2 = Richard P.
|last2 = Binzel
|first3 = Stephen M.
|last3 = Slivan
|first4 = Schelte J.
|last4 = Bus
|display-authors = 1
|title = An extension of the Bus asteroid taxonomy into the near-infrared
|journal = Icarus
|volume = 202
|issue = 1
|pages = 160–180
|year = 2011
|doi = 10.1016/j.icarus.2009.02.005
|bibcode = 2009Icar..202..160D
|url = http://www.tara.tcd.ie/bitstream/2262/43276/1/PEER_stage2_10.1016%252Fj.icarus.2009.02.005.pdf
|accessdate = 2013-03-22
|postscript = .
|url-status = dead
|archiveurl = https://web.archive.org/web/20140317200310/https://www.tara.tcd.ie/bitstream/2262/43276/1/PEER_stage2_10.1016/j.icarus.2009.02.005.pdf
|archivedate = 2014-03-17
}} See appendix A.
}}
External links
- {{AstDys|101}}
- {{JPL small body}}
{{Minor planets navigator |100 Hekate |number=101 |102 Miriam}}
{{Small Solar System bodies}}
{{Authority control}}
{{DEFAULTSORT:Helena}}
Category:Discoveries by James Craig Watson
{{S-beltasteroid-stub}}