(741081) 2005 LW3

(741081) 2005 LW₃ is a binary near-Earth asteroid classified as a potentially hazardous object of the Apollo group. It was discovered on 5 June 2005 by the Siding Spring Survey at Siding Spring Observatory in Australia.^[2] It made a close approach of 2.97 lunar distances (1.14×10^⁶ km; 0.71×10^⁶ mi) from Earth on 23 November 2022, reaching a peak brightness of apparent magnitude 13 as it passed over the northern celestial hemisphere sky.^[1] It was extensively observed by astronomers worldwide during the close approach, and radar observations by NASA's Goldstone Solar System Radar in California discovered a 100 m (330 ft)-wide natural satellite orbiting the asteroid at a wide separation of 4 km (2.5 mi).^[6][7]

(741081) 2005 LW₃

Radar image of 2005 LW3 and its satellite (below) by the Goldstone Solar System Radar on 23 November 2022
Discovery[1][2]
Discovered by	Siding Spring Survey
Discovery site	Siding Spring Obs.
Discovery date	5 June 2005
Designations
MPC designation	2005 LW3
Minor planet category	NEO · Apollo · PHA
Orbital characteristics[3]
Epoch 25 February 2023 (JD 2460000.5)
Uncertainty parameter 0
Observation arc	17.49 yr (6,389 days)[1]
Aphelion	2.106 AU
Perihelion	0.771 AU
Semi-major axis	1.439 AU
Eccentricity	0.4638
Orbital period (sidereal)	1.73 yr (630.3 days)
Mean anomaly	81.385°
Mean motion	0° 34m 16.171s / day
Inclination	6.021°
Longitude of ascending node	59.587°
Time of perihelion	5 October 2022
Argument of perihelion	288.663°
Earth MOID	0.001397 AU (209,000 km; 0.544 LD)
Jupiter MOID	3.335 AU
Physical characteristics
Mean diameter	400 m (primary)[4]
Synodic rotation period	3.6 h[4]
Geometric albedo	0.02[5]
Absolute magnitude (H)	21.89[3] · 21.68[1]

Physical characteristics

Goldstone Solar System Radar observations in November 2022 resolved the shape of 2005 LW₃, revealing a body 400 m (1,300 ft) in diameter—larger than its previously expected diameter of 150 m (490 ft).^[4][7] For an absolute magnitude of 21.9, this radar-measured diameter indicates that 2005 LW₃ has a very low geometric albedo of 0.02.^[5] These radar observations also determined a rotation period of 3.6 hours for 2005 LW₃.^[4]

Satellite

The satellite of 2005 LW₃ was discovered by a team of astronomers^[a] using Goldstone Solar System Radar observations from 23–27 November 2022. The satellite appears elongated, with equatorial dimensions of 100 m × 50 m (330 ft × 160 ft).^[4] The satellite is widely separated from 2005 LW₃ (the primary body of the system) at a semi-major axis of about 4 km (2.5 mi),^[4] which is around 17% of the primary's Hill radius (24 km or 15 mi for an assumed primary density of 1.6 g/cm³).^[5] The satellite's discovery was announced in a Central Bureau Electronic Telegram on 10 December 2022.^[4]

Notes

1. Observers credited for the discovery of the satellite include: S. P. Naidu, L. A. M. Benner, M. Brozovic, J. D. Giorgini, S. Horiuchi, I. Savill-Brown, J. Stevens, C. Phillips, P. Edwards, and E. Kruzins.^[4]