(374158) 2004 UL

(374158) 2004 UL is a sub-kilometer asteroid on an outstandingly eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group.^[2] The object is known for having the second-smallest perihelion of any known asteroid, after (137924) 2000 BD19.^{[citation needed]}

(374158) 2004 UL

Discovery[1]
Discovered by	LINEAR
Discovery site	Lincoln Lab's ETS
Discovery date	18 October 2004
Designations
MPC designation	(374158) 2004 UL
Alternative designations	2004 UL
Minor planet category	Apollo NEO PHA[1][2] Mercury crosser Venus crosser Earth crosser Mars crosser
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	15.05 yr (5,498 days)
Aphelion	2.4400 AU
Perihelion	0.0928 AU
Semi-major axis	1.2664 AU
Eccentricity	0.9267
Orbital period (sidereal)	1.43 yr (521 days)
Mean anomaly	320.92°
Mean motion	0° 41m 29.76s / day
Inclination	23.785°
Longitude of ascending node	39.575°
Argument of perihelion	149.57°
Earth MOID	0.0182 AU (7.1 LD)
Physical characteristics
Mean diameter	0.5–1.2 km (generic)[3] 0.516 km (calculated)[4]
Synodic rotation period	38±2 h[5][a]
Geometric albedo	0.20 (assumed)[4]
Spectral type	S[4]
Absolute magnitude (H)	18.77 (R)[b] 18.8[1][4]

It was discovered on 18 October 2004 by the Lincoln Near-Earth Asteroid Research (LINEAR) at Lincoln Lab's ETS near Socorro, New Mexico.^[2]

Orbit and classification

This Apollo asteroid orbits the Sun at a distance of 0.09–2.44 AU once every 17 months (521 days; semi-major axis of 1.27 AU). Its orbit has an outstandingly high eccentricity of 0.93 and an inclination of 24° with respect to the ecliptic.^[1]

Due to its orbit, it is also a Mercury-crosser, Venus-crosser and Mars-crosser. It has an Earth minimum orbital intersection distance of 0.0182 AU (2,720,000 km), which translates into 7.1 lunar distances.^[1]

Physical characteristics

2004 UL is an assumed stony S-type asteroid.^[4]

In October 2014, a rotational lightcurve for this asteroid was obtained from photometric observations by American astronomer Brian Warner at the CS3–Palmer Divide Station (U82) in Landers, California.^[a] It gave a longer-than average rotation period of 38±2 hours (most minor planets take 2–20 hours to complete a full rotation) with a high brightness variation of 1.2 magnitude, indicating a non-spheroidal shape (U=2).^[5]

Based on a generic magnitude-to-diameter conversion, 2004 UL measures between 0.5 and 1.2 kilometers.^[3] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 0.516 kilometers with an absolute magnitude of 18.8.^[4]

Numbering and naming

This minor planet was numbered by the Minor Planet Center on 18 October 2013 (M.P.C. 85347).^[6] As of 2018, it has not been named.^[2]

Notes

1. Lightcurve plot for (374158) by B. D. Warner at the CS3-Palmer Divide Station from October/November 2014
2. Jewitt (2013). Abs. magnitude of 18.77 (R). Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (374158)