2074 Shoemaker

2074 Shoemaker, provisional designation 1974 UA, is a stony Hungaria asteroid, Mars-crosser and suspected synchronous binary system from the innermost regions of the asteroid belt, approximately 4 kilometers in diameter. It was discovered on 17 October 1974, by astronomer Eleanor Helin at the Palomar Observatory.^[4] She named it after American astronomer Eugene Shoemaker.^[2]

2074 Shoemaker

Discovery[1]
Discovered by	E. F. Helin
Discovery site	Palomar Obs.
Discovery date	17 October 1974
Designations
MPC designation	(2074) Shoemaker
Named after	Eugene Shoemaker (American astronomer)[2]
Alternative designations	1974 UA
Minor planet category	Mars-crosser[3][4] · Hungaria[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	63.23 yr (23,096 days)
Aphelion	1.9472 AU
Perihelion	1.6521 AU
Semi-major axis	1.7996 AU
Eccentricity	0.0820
Orbital period (sidereal)	2.41 yr (882 days)
Mean anomaly	243.44°
Mean motion	0° 24m 29.88s / day
Inclination	30.080°
Longitude of ascending node	207.29°
Argument of perihelion	205.58°
Earth MOID	0.6680 AU · 260.2 LD
Physical characteristics
Dimensions	3.18±0.51 km[5] 3.217±0.558 km[1][6] 4.93 km (calculated)[3]
Synodic rotation period	2.5328±0.0004 h[7] 2.5331±0.0002 h[a][b] 2.5338±0.0002 h[8] 2.534±0.001 h[9] 2.809±0.001 h[10][c] 2.82±0.01 h[11] 57.02±0.10 h[12]
Geometric albedo	0.20 (assumed)[3] 0.41±0.13[5] 0.518±0.211[6]
Spectral type	SMASS = Sa[1] · S[3]
Absolute magnitude (H)	13.80[6] · 13.9[1][3] · 14.24[5] · 14.28±0.36[13]

Orbit and classification

Shoemaker is a bright member of the dynamical Hungaria group that forms the innermost dense concentration of asteroids in the Solar System.^[3] It orbits the Sun in the inner main-belt at a distance of 1.7–1.9 AU once every 2 years and 5 months (882 days). Its orbit has an eccentricity of 0.08 and an inclination of 30° with respect to the ecliptic.^[1] With a perihelion of 1.6521 AU, Shoemaker is a Mars-crossing asteroid as it crosses the orbit of Mars at 1.666 AU.^[1]

The body's observation arc begins with a precovery taken at Palomar in April 1954, more than 20 years prior to its official discovery observation.^[4]

Physical characteristics

In the SMASS classification, Shoemaker is a Sa-subtype, that transitions form the common stony S-type asteroids to the A-type asteroids.^[1]

Rotation period

Several rotational lightcurve of Shoemaker were obtained from photometric observations by American astronomer Brian Warner at his Palmer Divide Observatory (716) and CS3-Station (U82). Analysis of the best-rated lightcurves gave a well-defined rotation period of 2.5328 hours with a brightness amplitude of 0.13 magnitude (U=3).^[7][8][a]

Suspected binary

In October 2003, photometric observations of Shoemaker by Robert D. Stephens gave a long rotation period of 57.02 hours.^[12] After re-measuring the images with newer software and calibration techniques, two mutual occultation and eclipsing events were found, indicating that Shoemaker might be a synchronous binary asteroid with a minor-planet moon orbiting it every 55 hours.^[7] Observations in 2010, were difficult due to incomplete coverage and gave an orbital period of 27.39 hours for the secondary.^[8] Observations by astronomers at Etscorn Campus Observatory (719) in 2015, did not mention any mutual events.^[9]

In June 2017, Warner measured a rotation period of 2.5331±0.0002 hours and an orbital period for the secondary of 44.28 hours at his CS3-Palmer Divide Station in California.^[a][b] The binary nature of Shoemaker remains unconfirmed.

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Shoemaker measures 3.18 and 3.22 kilometers in diameter and its surface has an albedo between 0.41 and 0.52, respectively.^[5][6] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 4.93 kilometers based on an absolute magnitude of 13.9.^[3]

Naming

This minor planet was named by the discoverer after her colleague, the American astronomer Eugene Shoemaker (1928–1997), who was a discoverer of minor planets and of the Comet Shoemaker–Levy 9 that collided with Jupiter. He is well known for his work on impact craters and his role in the lunar Ranger, Surveyor and Apollo programs.^[2]

The naming was also proposed by Brian G. Marsden, the director of the Minor Planet Center (MPC).^[2] The official naming citation was published by the Minor Planet Center on 1 November 1978 (M.P.C. 4548).^[14]

Notes

1. Warner (2018b) web. Not yet in ADS. Observation 30 June 2017. Rotation period of 2.5331±0.0002 hours with a brightness amplitude of 0.09±0.01 mag. Quality code of 3. Summary figures for (2074) Shoemaker at Collaborative Asteroid Lightcurve Link (CALL)
2. Lightcurve plot of (2074) Shoemaker, Warner (2017), rotation period: 2.5331 hours; and second period (P2) of 44.28 hours. Quality code of 3.
3. Lightcurve plot of (2074) Shoemaker, Warner (2015), period: of 2.809 and 2.515 hours. Quality code of 2.