3996 Fugaku

3996 Fugaku, provisional designation 1988 XG₁, is a stony Florian asteroid from the inner regions of the asteroid belt, approximately 5.5 kilometers in diameter. It was discovered on 5 December 1988, by Japanese amateur astronomers Masaru Arai and Hiroshi Mori at Yorii Observatory in central Japan.^[9] It was named for Mount Fuji, Japan.^[2]

3996 Fugaku

Discovery[1]
Discovered by	M. Arai H. Mori
Discovery site	Yorii Obs.
Discovery date	5 December 1988
Designations
MPC designation	(3996) Fugaku
Named after	Mount Fuji (Japan)[2]
Alternative designations	1988 XG1 · 1939 FZ 1957 TB · 1981 SO5 1981 UM16
Minor planet category	main-belt · Flora[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	78.22 yr (28,570 days)
Aphelion	2.4941 AU
Perihelion	2.0254 AU
Semi-major axis	2.2597 AU
Eccentricity	0.1037
Orbital period (sidereal)	3.40 yr (1,241 days)
Mean anomaly	338.50°
Mean motion	0° 17m 24.36s / day
Inclination	2.2842°
Longitude of ascending node	90.755°
Argument of perihelion	156.18°
Physical characteristics
Dimensions	5.151±0.074 km[4] 5.231±0.032 km[5] 5.40 km (calculated)[3] 5.88±1.10 km[6]
Synodic rotation period	7.1912±0.0016 h[7]
Geometric albedo	0.24 (assumed)[3] 0.34±0.17[6] 0.4086±0.0152[5] 0.420±0.066[4]
Spectral type	S[3]
Absolute magnitude (H)	13.0[1][5][6] · 13.055±0.003 (R)[7] · 13.5[3] · 13.57±0.25[8]

Orbit and classification

Fugaku is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.0–2.5 AU once every 3 years and 5 months (1,241 days). Its orbit has an eccentricity of 0.10 and an inclination of 2° with respect to the ecliptic.^[1] It was first identified as 1939 FZ at Turku Observatory in 1939, extending the asteroid's observation arc by 49 years prior to its official discovery observation.^[9]

Physical characteristics

Fugaku has been characterized as a stony S-type asteroid, the most common type in the inner main-belt.^[1]

Rotation period

In March 210, a rotational lightcurve of Fugaku was obtained from photometric observations at the Palomar Transient Factory in California. It gave a rotation period of 7.1912 hours with a change in brightness of 0.86 magnitude (U=2).^[7]

Diameter and albedo

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Fugaku measures between 5.15 and 5.88 kilometers in diameter, and its surface has an albedo between 0.34 and 0.42.^[4][5][6] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the largest member and namesake of this family – and calculates a diameter of 5.40 kilometers with an absolute magnitude of 13.5.^[3]

Naming

This minor planet was named for the ancient name of Mount Fuji, Japan's highest mountain and a well-known symbol. Another minor planet, 1584 Fuji, is also named for this mountain.^[2] The official naming citation was published by the Minor Planet Center on 4 May 1999 (M.P.C. 34619).^[10]