# (159857) 2004 LJ1

(159857) 2004 LJ$_1$, provisional designation 2004 LJ$_1$, is an asteroid on an eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 3 kilometers in diameter. The asteroid was discovered on 10 June 2004, by astronomers of the LINEAR program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States. It is one of the largest potentially hazardous asteroids known to exist.

## Orbit and classification

2004 LJ$_1$ is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of near-Earth objects.
The body orbits the Sun at a distance of 0.9–3.6 AU once every 3 years and 5 months (1,244 days; semi-major axis of 2.26 AU). Its orbit has an eccentricity of 0.59 and an inclination of 23° with respect to the ecliptic. Its observation arc begins with a precovery from the Digitized Sky Survey taken at the Siding Spring Observatory, Australia, in February 1995, more than 9 years prior to its official discovery observation at Socorro.

### Close approaches

With an absolute magnitude of at least 15.4, 2004 LJ$_1$ is one of the brightest and presumably largest known potentially hazardous asteroid (see PHA-list). It has an Earth minimum orbital intersection distance of 0.0168 AU (2,510,000 km), which translates into 6.5 lunar distances (LD). On 16 November 2038, this asteroid will make its closest near-Earth encounter at a nominal distance of 0.0198 AU (7.7 LD). It is also classified as a Mars-crosser, crossing the orbit of the Red Planet at 1.66 AU.
| PHA | Date | Approach distance in lunar distances | Approach distance in lunar distances | Approach distance in lunar distances | Abs. mag (H) | Diameter $^{(C)}$ (m) | Ref $^{(D)}$ |
| PHA | Date | Nominal $^{(B)}$ | Minimum | Maximum | Abs. mag (H) | Diameter $^{(C)}$ (m) | Ref $^{(D)}$ |
| (143651) 2003 QO104 | 1981-05-18 | 2.761 | 2.760 | 2.761 | 16.0 | 1333–4306 | data |
| 2014 LJ21 | 1989-08-01 | 7.034 | 6.843 | 7.224 | 16.0 | 1333–4306 | data |
| 4179 Toutatis | 1992-12-08 | 9.399 | 9.399 | 9.399 | 15.30 | 2440–2450 | data |
| 4179 Toutatis | 2004-09-29 | 4.031 | 4.031 | 4.031 | 15.30 | 2440–2450 | data |
| (159857) 2004 LJ1 | 2038-11-16 | 7.719 | 7.719 | 7.719 | 15.4 | 1746–4394 | data |
| (4953) 1990 MU | 2058-06-05 | 8.986 | 8.984 | 8.988 | 14.1 | 3199–10329 | data |
| 4179 Toutatis | 2069-11-05 | 7.725 | 7.724 | 7.725 | 15.30 | 2440–2450 | data |
| (52768) 1998 OR2 | 2079-04-16 | 4.611 | 4.611 | 4.612 | 15.8 | 1462–4721 | data |
| (415029) 2011 UL21 | 2089-06-25 | 6.936 | 6.935 | 6.938 | 15.7 | 1531–4944 | data |
| 3200 Phaethon | 2093-12-14 | 7.714 | 7.709 | 7.718 | 14.6 | 4900–5300 | data |
| (52768) 1998 OR2 | 2127-04-16 | 6.536 | 6.510 | 6.563 | 15.8 | 1462–4721 | data |
| $^{(A)}$ This list includes near-Earth approaches of less than 10 lunar distances (LD) of objects with H brighter than 16. $^{(B)}$ Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km). $^{(C)}$ Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y. $^{(D)}$ Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD) $^{(E)}$ Color codes: unobserved at close approach observed during close approach upcoming approaches ||||||||

## Physical characteristics

2004 LJ$_1$ is an assumed stony S-type asteroid.

### Rotation period

Three rotational lightcurves of 2004 LJ$_1$ have been obtained from photometric observations by Johanna Torppa, Adrián Galád and Brian Warner since 2004. Lightcurve analysis gave a consolidated rotation period of 2.7247 hours with a brightness amplitude between 0.15 and 0.59 magnitude (U=3).

### Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, 2004 LJ$_1$ measures 3.07 kilometers in diameter and its surface has an albedo of 0.13. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 2.47 kilometers, based on an absolute magnitude of 15.4.

## Numbering and naming

This minor planet was numbered by the Minor Planet Center on 30 June 2007. As of 2018, it has not been named.