3451 Mentor

Shape model of Mentor from its lightcurve
Discovery [1]
Discovered by	A. Mrkos
Discovery site	Kleť Obs.
Discovery date	19 April 1984
Designations
MPC designation	(3451) Mentor
Pronunciation	/ˈmɛntɔːr/[2]
Named after	Mentor (Greek mythology)[1]
Alternative designations	1984 HA1 · 1950 HG1
Minor planet category	Jupiter trojan [1][3][4] Trojan [5][6] · background [6]
Adjectives	Mentorian
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	35.19 yr (12,853 d)
Aphelion	5.4935 AU
Perihelion	4.7828 AU
Semi-major axis	5.1382 AU
Eccentricity	0.0692
Orbital period (sidereal)	11.65 yr (4,254 d)
Mean anomaly	236.39°
Mean motion	0° 5m 4.56s / day
Inclination	24.654°
Longitude of ascending node	179.66°
Argument of perihelion	131.49°
Jupiter MOID	0.0573 AU
TJupiter	2.8150
Physical characteristics
Mean diameter	116.30 km (calculated)[4] 117.91±3.19 km[7] 126.29±1.64 km[8]
Synodic rotation period	7.700±0.019 h[9] 7.702±0.002 h[10][a] 7.730±0.001 h[11][a]
Geometric albedo	0.044±0.008[8] 0.057 (assumed)[4] 0.075±0.005[7]
Spectral type	X (SMASS)[12] X (SDSS-MOC)[13] X (Pan-STARRS)[4][14] P (WISE)[4] C (assumed)[4] B–V = 0.730±0.060[15] V–R = 0.380±0.040[15] V–I = 0.770±0.020[4]
Absolute magnitude (H)	8.10[7] 8.4[1][3][4] 8.5[8] 8.71±0.29[14]

3451 Mentor /ˈmɛntɔːr/ is a large Jupiter trojan from the Trojan camp, approximately 120 kilometers (75 miles) in diameter. It was discovered on 19 April 1984, by Czech astronomer Antonín Mrkos at the Kleť Observatory in the Czech Republic. The uncommon Jovian X-type asteroid is one of the largest Jupiter trojans and has a rotation period of 7.7 hours.^[4] It was named after Mentor from Greek mythology.^[1] Mentor, a man who was rich in horse at Pedaeus. He was the father of the spearman Imbrius, an ally of the Trojans.^[16]

Orbit and classification

Mentor is a large Jovian asteroid orbiting in the trailing Trojan camp at Jupiter's L₅ Lagrangian point, 60° behind its orbit in a 1:1 resonance (see Trojans in astronomy).^[5] It is also a non-family asteroid of the Jovian background population.^[6][12]

It orbits the Sun at a distance of 4.8–5.5 AU once every 11 years and 8 months (4,254 days; semi-major axis of 5.14 AU). Its orbit has an eccentricity of 0.07 and an inclination of 25° with respect to the ecliptic.^[3] The asteroid was first observed as 1950 HG₁ at Simeiz Observatory in April 1950. The body's observation arc begins at Crimea–Nauchnij in March 1983, one year prior to its official discovery observation at Klet.^[1]

Physical characteristics

Mentor is an X-type asteroid, according to the SMASS classification, the SDSS-based taxonomy and observations by Pan-STARRS.^[4][12][13] It has also been characterized as a primitive P-type asteroid by the Wide-field Infrared Survey Explorer (WISE), and as an assumed, carbonaceous C-type by the Collaborative Asteroid Lightcurve Link (CALL). Its V–I color index of 0.77 is notably lower than that of a Jovian D-type asteroid, which is the dominant spectral type among the Jupiter trojans (also see table below).^[4]

Rotation period

A large number of rotational lightcurves of Mentor have been obtained,^[4] since its first photometric observations by William Hartmann (1988).^[17] The first rotation period of 7.675±0.019 hours with a brightness variation of 0.18±0.01 was reported by Stefano Mottola, who observed Mentor in February 1993, using the former ESO 1-metre telescope at the La Silla Observatory in Chile (U=3-). Follow-up observations by Mottola at the Calar Alto Observatory in July 1998 gave a refined period of 7.700±0.019 hours and an amplitude of 0.15±0.01 magnitude (U=3).^[9]

In 2006 and 2007, photometric observations of Mentor were made at the Roque de los Muchachos (7.68 and 7.682 h) and Oakley Observatory (7.70 h).^[18][19][20] Additional period determinations by Laurent Bernasconi (7.699 h) Federico Manzini (>6 h) and René Roy (7.727 and 7.6 h) were made between 2006 and 2010, and reported at Behrend's website.^[21] In 2012, observations in the R- and S-band at the Palomar Transient Factory gave a period of 7.694 and 7.677 hours (U=2/3).^[22]

Follow-up observations by Daniel Coley and Robert Stephens at GMARS (G79) in 2010, and the Center for Solar System Studies during 2013–2017, measured four well-defined periods including 7.702±0.002 and 7.730±0.001 hours with a brightness amplitude of 0.46 and 0.21 magnitude, respectively (U=3/3-/3-/3).^{[10][11][23][24][a]}

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telescope, Mentor measures 117.91 and 126.29 kilometers in diameter and its surface has an albedo of 0.075 and 0.044, respectively.^[7][8] CALL assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 116.30 kilometers based on an absolute magnitude of 8.4.^[4] Mentor together with 624 Hektor and 884 Priamus are the three largest Jupiter trojans for which the Supplemental IRAS Minor Planet Survey (SIMPS), conducted by IRAS, provides no data (in the table below, placeholder figures from the LCDB are shown instead).^[25]

Naming

This minor planet was named by the discoverer from Greek mythology after Mentor, father of Imbrius and son of spearman Imbrus at Pedaseus. Mentor fought with the Trojans against the Greeks in the Trojan War.^[1] In Homer's Iliad, he was described as a man who was rich in horse. The official naming citation was published by the Minor Planet Center on 29 November 1993 (M.P.C. 22829).^[26]