View source for 2005 HC4

{{Short description|Asteroid}}
{{DISPLAYTITLE:{{mp|2005 HC|4}}}}
{{Use dmy dates|date=June 2017}}
{{Infobox planet
| minorplanet=yes
| background=#FFC2E0
| name={{mp|2005 HC|4}}
| image= Orbit of 2005 HC4.gif
| image_scale=
| discovery_ref=<ref name="MPEC2005-J02"/>
| discoverer=[[LONEOS]]
| discovered=30 April 2005
| alt_names=
| mp_category={{Ubl
 | [[List of Mercury-crossing minor planets|Mercury Crosser]]
 | [[List of Venus-crossing minor planets|Venus Crosser]]
 | [[Apollo Asteroid]]
 | [[List of Mars-crossing minor planets|Mars Crosser]]
 }}
| orbit_ref=<ref name="jpldata"/>
| epoch=3 May 2005 ([[Julian day|JD]]&nbsp;2453493.5)
| semimajor={{Convert|1.8207|AU|Gm|abbr=on}}
| perihelion={{Convert|0.070657|AU|Gm|abbr=on}}
| aphelion={{Convert|3.5707|AU|Gm|abbr=on|lk=on}}
| eccentricity=0.96119
| period=2.46&nbsp;[[Julian year (astronomy)|yr]] (897.30&nbsp;[[Julian year (astronomy)|d]])
| inclination=8.3967°
| asc_node=63.790°
| arg_peri=309.01°
| mean_anomaly=341.42[[Degree (angle)|°]]
| dimensions=210–480&nbsp;m<ref name=neodys />
| escape_velocity=
| rotation=
| spectral_type=
| abs_magnitude=20.7
| mean_motion={{Deg2DMS|0.40120|sup=ms}} /day
| uncertainty=9
| moid={{Convert|0.0615074|AU|Gm|abbr=on}}
| jupiter_moid={{Convert|1.92798|AU|Gm|abbr=on}}
}}

'''2005 HC<sub>4</sub>''' is the asteroid with the smallest known [[perihelion]] of any known object orbiting the [[Sun]] (except [[sungrazing comet]]s). Its extreme orbital [[Eccentricity (orbit)|eccentricity]] brings it to within 0.071&nbsp;[[Astronomical unit|AU]] of the Sun (23% of [[Mercury (planet)|Mercury]]'s perihelion) and takes it as far as 3.562&nbsp;AU from the Sun (well beyond the orbit of [[Mars]]). Due to its very small perihelion and comparably large aphelion, {{mp|2005 HC|4}} achieves the fastest speed of any known asteroid bound to the Solar System with a velocity of 157&nbsp;km/s (565,000&nbsp;km/h; 351,000&nbsp;mi/h) at perihelion<ref>As calculated with the vis-viva-equation : <math>v^2 = GM \left({ 2 \over r} - {1 \over a}\right)</math>
where:

* ''v'' is the relative speed of the two bodies
* ''r'' is the distance between the two bodies
* ''a'' is the [[semi-major axis]] (''a'' > 0 for [[ellipse]]s, ''a'' = &infin; or 1/''a'' = 0 for [[parabola]]s, and ''a'' < 0 for [[hyperbola]]s)
* ''G'' is the [[gravitational constant]]
* ''M'' is the mass of the central body</ref> (there are [[comet]]s, however, which obtain much higher speeds).

== See also==
* [[List of Mercury-crossing minor planets]]
* [[List of Venus-crossing minor planets]]
* [[Apollo asteroids]]
* [[List of Mars-crossing minor planets]]

== References ==
{{reflist
| refs =

<ref name=jpldata>{{cite web
  |type=2005-05-11 last obs (arc=11 days)
  |title=JPL Small-Body Database Browser: (2005 HC4)
  |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2005%20HC4
  |publisher=[[Jet Propulsion Laboratory]]
  |accessdate=30 March 2016}}</ref>

<ref name="MPEC2005-J02">{{Cite web
  |title=MPEC 2005-J02 : 2005 HC4
  |publisher=[[IAU Minor Planet Center]]
  |date=2005-05-01
  |url=http://www.minorplanetcenter.org/mpec/K05/K05J02.html
  |accessdate=2014-03-05}} (K05H04C)</ref>

<ref name=neodys>{{Cite web
  |title=NEODyS 2005 HC4
  |publisher=Near Earth Objects{{Snd}} Dynamic Site
  |url=https://newton.spacedys.com/neodys/index.php?pc=1.1.9&n=2005HC4
  |accessdate=2014-03-07}}</ref>

}} <!-- end of reflist -->

== External links ==
* {{NeoDys|2005+HC4}}
* {{ESA-SSA|2005HC4}}
* {{JPL small body}}

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{{Small Solar System bodies}}
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{{DEFAULTSORT:2005 HC4}}
[[Category:Apollo asteroids|#]]
[[Category:Minor planet object articles (unnumbered)]]
[[Category:Mercury-crossing asteroids]]
[[Category:Venus-crossing asteroids]]
[[Category:Astronomical objects discovered in 2005|20050430]]


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