2005 HC4 explained

Minorplanet:	yes
Background:	FFC2E0
Discoverer:	LONEOS
Discovered:	30 April 2005
Epoch:	3 May 2005 (JD 2453493.5)
Semimajor:	1.8207AU
Perihelion:	0.070657AU
Aphelion:	3.5707abbr=onNaNabbr=on
Eccentricity:	0.96119
Period:	2.46 yr (897.30 d)
Inclination:	8.3967°
Asc Node:	63.790°
Arg Peri:	309.01°
Mean Anomaly:	341.42°
Dimensions:	210–480 m
Abs Magnitude:	20.7
Mean Motion:	/day
Uncertainty:	9
Moid:	0.0615074AU
Jupiter Moid:	1.92798AU

2005 HC₄ is the asteroid with the smallest known perihelion of any known object orbiting the Sun (except sungrazing comets). Its extreme orbital eccentricity brings it to within 0.071 AU of the Sun (23% of Mercury's perihelion) and takes it as far as 3.562 AU from the Sun (well beyond the orbit of Mars). Due to its very small perihelion and comparably large aphelion, achieves the fastest speed of any known asteroid bound to the Solar System with a velocity of 157 km/s (565,000 km/h; 351,000 mi/h) at perihelion^[1] (there are comets, 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

Notes and References

1. As calculated with the vis-viva-equation : v ^{2} = GM \left({ 2 \over r} - { 1 \over a}\right) 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 ellipses, a = ∞ or 1/a = 0 for parabolas, and a < 0 for hyperbolas)
   • G is the gravitational constant
   • M is the mass of the central body