(5407) 1992 AX

(5407) 1992 AX, provisional designation 1992 AX, is a stony asteroid and a synchronous binary Mars-crosser from the innermost region of the asteroid belt, approximately 3.6 kilometers (2.2 miles) in diameter. It was discovered on 4 January 1992, by Japanese astronomers Seiji Ueda and Hiroshi Kaneda at the Kushiro Observatory on Hokkaidō, Japan.^[1] The S-type asteroid has a short rotation period of 2.5 hours.^[4] Its sub-kilometer satellite was discovered in 1997.^[5] As of 2018, the binary system has not been named.^[1]

(5407) 1992 AX

Orbital diagram of 1992 AX
Discovery[1]
Discovered by	S. Ueda H. Kaneda
Discovery site	Kushiro Obs.
Discovery date	4 January 1992
Designations
MPC designation	(5407) 1992 AX
Alternative designations	1992 AX · 1987 BH2
Minor planet category	Mars crosser[1][2][3] binary[4][5]
Orbital characteristics[2]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 0
Observation arc	66.90 yr (24,434 d)
Aphelion	2.3486 AU
Perihelion	1.3279 AU
Semi-major axis	1.8383 AU
Eccentricity	0.2776
Orbital period (sidereal)	2.49 yr (910 d)
Mean anomaly	263.87°
Mean motion	0° 23m 43.8s / day
Inclination	11.390°
Longitude of ascending node	117.74°
Argument of perihelion	108.78°
Known satellites	1 (D: 780 m; P: 13.52 h)[4][5]
Earth MOID	0.377 AU (147 LD)
Physical characteristics
Mean diameter	2.78±0.55 km[6] 3.60±0.36 km[7] 3.8±0.4 km[8] 4.18±0.12 km[9]
Synodic rotation period	2.5488 h[10][11]
Geometric albedo	0.199[8] 0.294[9] 0.376[7] 0.40[6]
Spectral type	SMASS = Sk[2] · S[12] B–V = 0.690[10] V–R = 0.500[10] V–I = 0.840[10]
Absolute magnitude (H)	13.90[7][9] 14.0[1][2] 14.47[8][10]

Orbit and classification

1992 AX a member of the Mars-crossing asteroids, a dynamically unstable group between the main belt and the near-Earth populations, crossing the orbit of Mars at 1.66 AU.^[1][3] It orbits the Sun at a distance of 1.3–2.3 AU once every 2 years and 6 months (910 days; semi-major axis of 1.84 AU). Its orbit has an eccentricity of 0.28 and an inclination of 11° with respect to the ecliptic.^[2]

The asteroid makes occasional close approaches to Mars. Its next close approach, on 22 January 2027, will bring it 11,260,000 km (0.0753 AU) from Mars.^[2] The body's observation arc begins with a precovery taken at Palomar Observatory in November 1951, or more than 40 years prior to its official discovery observation at Kushiro.^[1]

Naming

This minor planet was numbered by the Minor Planet Center on 9 December 1992 (M.P.C. 21249).^[13] As of 2018, it has not been named.^[1]

Physical characteristics

1992 AX has been characterized as a common, stony S-type asteroid.^[12] In the SMASS taxonomy, it is an Sk-subtype, that transitions between the S and K-type asteroids.^[2] The body's color indices of 0.690 (B–V), 0.500 (V–R) and 0.840 (V–I) were also determined.^[10]

Lightcurves

Rotation period

Since 1997, several rotational lightcurves of 1992 AX have been obtained from photometric observations by Petr Pravec and collaborating astronomers. Best-rated lightcurve analysis gave a rotation period of 2.5488 hours with a consolidated brightness amplitude between 0.10 and 0.12 magnitude (U=2/3).^[4][10][11] The results supersedes a tentative period determination of 3.6 hours by Marc Buie (U=1).^[4]

Satellite

During the observations in January 1997, it was also revealed that 1992 AX is a synchronous binary asteroid with a minor-planet moon in its orbit.^[10] The satellite measures approximately 780 meters in diameter, or about 20% of its primary, and has an orbital period of 13.52 hours with an estimated semi-major axis of 5.8 kilometers for its very circular orbit.^[5] Observations by Pravec in January and February 2012 confirmed the binary nature of this asteroid, as well as its rotational and orbital periods.^[4]

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite, the Spitzer Space Telescope and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), 1992 AX measures between 2.78 and 4.18 kilometers in diameter and its surface has an albedo between 0.199 and 0.40.^[6][8][9]

In 2017, a study by WISE dedicated to Mars-crossing asteroids determined a diameter of 3.60 kilometers with a high albedo of 0.376.^[7] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.20 and derives a diameter of 3.79 kilometers based on an absolute magnitude of 14.47.^[4] The Johnston's archive gives an effective (combined) diameter of 3.98 kilometers with 3.9 and 0.78 kilometers for is primary and secondary body, respectively.^[3][5]