# 5144 Achates

5144 Achates /əˈkeɪtiːz/ is a large Jupiter trojan from the Trojan camp, approximately 90 kilometers (56 miles) in diameter. It was discovered on 2 December 1991, by American astronomer Carolyn Shoemaker at the Palomar Observatory in southern California, United States. The assumed C-type asteroid has a rotation period of 6 hours, a notably eccentric orbit of 0.27, and belongs to the 40 largest Jupiter trojans. It was named after Achates from Greco-Roman mythology.

## Orbit and classification

Achates is a dark Jovian asteroid orbiting in the trailing Trojan camp at Jupiter's L$_5$ Lagrangian point, 60° behind its orbit in a 1:1 resonance (see Trojans in astronomy). This Jupiter trojan is also a non-family asteroid of the Jovian background population.
It orbits the Sun at a distance of 3.8–6.6 AU once every 11 years and 10 months (4,331 days; semi-major axis of 5.2 AU). Its orbit has a high eccentricity of 0.27 and an inclination of 9° with respect to the ecliptic. Achates has the most eccentric orbit of all larger Jupiter trojans with an absolute magnitude brighter than 11.
The asteroid was first observed as 1939 PC at Nice Observatory in August 1939. The body's observation arc begins with a precovery taken at the Goethe Link Observatory in May 1949, or more than 42 years prior to its official discovery observation at Palomar.

## Physical characteristics

Achates is an assumed, carbonaceous C-type asteroid.

### Rotation period

Several rotational lightcurve of Achates have been obtained from photometric observations by Robert Stephens, Stefano Mottola and Lawrence Molnar since 1992. The best-rated measurement made at the robotic Calvin–Rehoboth Observatory in February 2007, gave a rotation period of 5.958 hours with a brightness amplitude of 0.32 magnitude (U=3).

### Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, and the Infrared Astronomical Satellite IRAS, Achates measures between 80.96 and 91.91 kilometers in diameter and its surface has an albedo between 0.0576 and 0.074. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0526 and a diameter of 91.82 kilometers based on an absolute magnitude of 9.0.
Largest Jupiter Trojans by survey$^{(A)}$ (mean-diameter in kilometers; YoD: Year of Discovery) :
| Designation | H | WISE | IRAS | Akari | Ln | RP | V–I | YoD | Ref |
| 624 Hektor | 7.2 | 225 | 233 | 230.99 | L4 | 6.92 | 0.930 | 1907 | list |
| 617 Patroclus | 8.19 | 140.362 | 140.92 | 140.85 | L5 | 102.80 | 0.830 | 1906 | list |
| 911 Agamemnon | 7.89 | 131.038 | 166.66 | 185.30 | L4 | 6.59 | 0.980 | 1919 | list |
| 588 Achilles | 8.67 | 130.099 | 135.47 | 133.22 | L4 | 7.31 | 0.940 | 1906 | list |
| 3451 Mentor | 8.4 | 126.288 | 116.30 | 117.91 | L5 | 7.70 | 0.770 | 1984 | list |
| 3317 Paris | 8.3 | 118.790 | 116.26 | 120.45 | L5 | 7.09 | 0.950 | 1984 | list |
| 1867 Deiphobus | 8.3 | 118.220 | 122.67 | 131.31 | L5 | 58.66 | 0.930 | 1971 | list |
| 1172 Äneas | 8.33 | 118.020 | 142.82 | 148.66 | L5 | 8.71 | 0.950 | 1930 | list |
| 1437 Diomedes | 8.3 | 117.786 | 164.31 | 172.60 | L4 | 24.49 | 0.810 | 1937 | list |
| 1143 Odysseus | 7.93 | 114.624 | 125.64 | 130.81 | L4 | 10.11 | 0.860 | 1930 | list |
| 2241 Alcathous | 8.64 | 113.682 | 114.63 | 118.87 | L5 | 7.69 | 0.940 | 1979 | list |
| 659 Nestor | 8.99 | 112.320 | 108.87 | 107.06 | L4 | 15.98 | 0.790 | 1908 | list |
| 3793 Leonteus | 8.7 | 112.046 | 86.26 | 87.58 | L4 | 5.62 | 0.780 | 1985 | list |
| 3063 Makhaon | 8.4 | 111.655 | 116.14 | 114.34 | L4 | 8.64 | 0.830 | 1983 | list |
| 1583 Antilochus | 8.6 | 108.842 | 101.62 | 111.69 | L4 | 31.54 | 0.950 | 1950 | list |
| 884 Priamus | 8.81 | 101.093 | 96.29 | 119.99 | L5 | 6.86 | 0.900 | 1917 | list |
| 1208 Troilus | 8.99 | 100.477 | 103.34 | 111.36 | L5 | 56.17 | 0.740 | 1931 | list |
| 1173 Anchises | 8.89 | 99.549 | 126.27 | 120.49 | L5 | 11.60 | 0.780 | 1930 | list |
| 2207 Antenor | 8.89 | 97.658 | 85.11 | 91.32 | L5 | 7.97 | 0.950 | 1977 | list |
| 2363 Cebriones | 9.11 | 95.976 | 81.84 | 84.61 | L5 | 20.05 | 0.910 | 1977 | list |
| 4063 Euforbo | 8.7 | 95.619 | 102.46 | 106.38 | L4 | 8.85 | 0.950 | 1989 | list |
| 2357 Phereclos | 8.94 | 94.625 | 94.90 | 98.45 | L5 | 14.39 | 0.960 | 1981 | list |
| 4709 Ennomos | 8.5 | 91.433 | 80.85 | 80.03 | L5 | 12.28 | 0.690 | 1988 | list |
| 2797 Teucer | 8.7 | 89.430 | 111.14 | 113.99 | L4 | 10.15 | 0.920 | 1981 | list |
| 2920 Automedon | 8.8 | 88.574 | 111.01 | 113.11 | L4 | 10.21 | 0.950 | 1981 | list |
| 15436 Dexius | 9.1 | 87.646 | 85.71 | 78.63 | L4 | 8.97 | 0.870 | 1998 | list |
| 3596 Meriones | 9.2 | 87.380 | 75.09 | 73.28 | L4 | 12.96 | 0.830 | 1985 | list |
| 2893 Peiroos | 9.23 | 86.884 | 87.46 | 86.76 | L5 | 8.96 | 0.950 | 1975 | list |
| 4086 Podalirius | 9.1 | 85.495 | 86.89 | 85.98 | L4 | 10.43 | 0.870 | 1985 | list |
| 4060 Deipylos | 9.3 | 84.043 | 79.21 | 86.79 | L4 | 9.30 | 0.760 | 1987 | list |
| 1404 Ajax | 9.3 | 83.990 | 81.69 | 96.34 | L4 | 29.38 | 0.960 | 1936 | list |
| 4348 Poulydamas | 9.5 | 82.032 | 70.08 | 87.51 | L5 | 9.91 | 0.840 | 1988 | list |
| 5144 Achates | 9.0 | 80.958 | 91.91 | 89.85 | L5 | 5.96 | 0.920 | 1991 | list |
| 4833 Meges | 8.9 | 80.165 | 87.33 | 89.39 | L4 | 14.25 | 0.940 | 1989 | list |
| 2223 Sarpedon | 9.41 | 77.480 | 94.63 | 108.21 | L5 | 22.74 | 0.880 | 1977 | list |
| 4489 Dracius | 9.0 | 76.595 | 92.93 | 95.02 | L4 | 12.58 | 0.950 | 1988 | list |
| 2260 Neoptolemus | 9.31 | 76.435 | 71.65 | 81.28 | L4 | 8.18 | 0.950 | 1975 | list |
| 5254 Ulysses | 9.2 | 76.147 | 78.34 | 80.00 | L4 | 28.72 | 0.970 | 1986 | list |
| 3708 Socus | 9.3 | 75.661 | 79.59 | 76.75 | L5 | 6.55 | 0.980 | 1974 | list |
| 2674 Pandarus | 9.1 | 74.267 | 98.10 | 101.72 | L5 | 8.48 | 1.000 | 1982 | list |
| 3564 Talthybius | 9.4 | 73.730 | 68.92 | 74.11 | L4 | 40.59 | 0.900 | 1985 | list |
| 4834 Thoas | 9.1 | 72.331 | 86.82 | 96.21 | L4 | 18.19 | 0.950 | 1989 | list |
| 7641 Cteatus | 9.4 | 71.839 | 68.97 | 75.28 | L4 | 27.77 | 0.980 | 1986 | list |
| 3540 Protesilaos | 9.3 | 70.225 | 76.84 | 87.66 | L4 | 8.95 | 0.940 | 1973 | list |
| 11395 Iphinous | 9.8 | 68.977 | 64.71 | 67.78 | L4 | 17.38 | – | 1998 | list |
| 4035 Thestor | 9.6 | 68.733 | 68.23 | 66.99 | L4 | 13.47 | 0.970 | 1986 | list |
| 5264 Telephus | 9.4 | 68.472 | 73.26 | 81.38 | L4 | 9.53 | 0.970 | 1991 | list |
| 1868 Thersites | 9.5 | 68.163 | 70.08 | 78.89 | L4 | 10.48 | 0.960 | 1960 | list |
| 9799 Thronium | 9.6 | 68.033 | 64.87 | 72.42 | L4 | 21.52 | 0.910 | 1996 | list |
| 4068 Menestheus | 9.5 | 67.625 | 62.37 | 68.46 | L4 | 14.40 | 0.950 | 1973 | list |
| 23135 Pheidas | 9.9 | 66.230 | 58.29 | 68.50 | L4 | 8.69 | 0.860 | 2000 | list |
| 2456 Palamedes | 9.3 | 65.916 | 91.66 | 99.60 | L4 | 7.24 | 0.920 | 1966 | list |
| 3709 Polypoites | 9.1 | 65.297 | 99.09 | 85.23 | L4 | 10.04 | 1.000 | 1985 | list |
| 1749 Telamon | 9.5 | 64.898 | 81.06 | 69.14 | L4 | 16.98 | 0.970 | 1949 | list |
| 3548 Eurybates | 9.6 | 63.885 | 72.14 | 68.40 | L4 | 8.71 | 0.730 | 1973 | list |
| 4543 Phoinix | 9.7 | 63.836 | 62.79 | 69.54 | L4 | 38.87 | 1.200 | 1989 | list |
| 12444 Prothoon | 9.8 | 63.835 | 64.31 | 62.41 | L5 | 15.82 | – | 1996 | list |
| 4836 Medon | 9.5 | 63.277 | 67.73 | 78.70 | L4 | 9.82 | 0.920 | 1989 | list |
| 16070 Charops | 9.7 | 63.191 | 64.13 | 68.98 | L5 | 20.24 | 0.960 | 1999 | list |
| 15440 Eioneus | 9.6 | 62.519 | 66.48 | 71.88 | L4 | 21.43 | 0.970 | 1998 | list |
| 4715 Medesicaste | 9.7 | 62.097 | 63.91 | 65.93 | L5 | 8.81 | 0.850 | 1989 | list |
| 34746 Thoon | 9.8 | 61.684 | 60.51 | 63.63 | L5 | 19.63 | 0.950 | 2001 | list |
| 38050 Bias | 9.8 | 61.603 | 61.04 | 50.44 | L4 | 18.85 | 0.990 | 1998 | list |
| 5130 Ilioneus | 9.7 | 60.711 | 59.40 | 52.49 | L5 | 14.77 | 0.960 | 1989 | list |
| 5027 Androgeos | 9.6 | 59.786 | 57.86 | n.a. | L4 | 11.38 | 0.910 | 1988 | list |
| 6090 Aulis | 9.4 | 59.568 | 74.53 | 81.92 | L4 | 18.48 | 0.980 | 1989 | list |
| 5648 Axius | 9.7 | 59.295 | 63.91 | n.a. | L5 | 37.56 | 0.900 | 1990 | list |
| 7119 Hiera | 9.7 | 59.150 | 76.40 | 77.29 | L4 | 400 | 0.950 | 1989 | list |
| 4805 Asteropaios | 10.0 | 57.647 | 53.16 | 43.44 | L5 | 12.37 | – | 1990 | list |
| 16974 Iphthime | 9.8 | 57.341 | 55.43 | 57.15 | L4 | 78.9 | 0.960 | 1998 | list |
| 4867 Polites | 9.8 | 57.251 | 58.29 | 64.29 | L5 | 11.24 | 1.010 | 1989 | list |
| 2895 Memnon | 10.0 | 56.706 | 55.67 | n.a. | L5 | 7.50 | 0.710 | 1981 | list |
| 4708 Polydoros | 9.9 | 54.964 | 55.67 | n.a. | L5 | 7.52 | 0.960 | 1988 | list |
| (21601) 1998 XO89 | 10.0 | 54.909 | 55.67 | 56.08 | L4 | 12.65 | 0.970 | 1998 | list |
| 12929 Periboea | 9.9 | 54.077 | 61.04 | 55.34 | L5 | 9.27 | 0.880 | 1999 | list |
| 17492 Hippasos | 10.0 | 53.975 | 55.67 | n.a. | L5 | 17.75 | – | 1991 | list |
| 5652 Amphimachus | 10.1 | 53.921 | 53.16 | 52.48 | L4 | 8.37 | 1.050 | 1992 | list |
| 2759 Idomeneus | 9.9 | 53.676 | 61.01 | 52.55 | L4 | 32.38 | 0.910 | 1980 | list |
| 5258 Rhoeo | 10.2 | 53.275 | 50.77 | n.a. | L4 | 19.85 | 1.010 | 1989 | list |
| (12126) 1999 RM11 | 10.1 | 53.202 | n.a. | n.a. | L5 | n.a. | ? | 1999 | list |
| (15502) 1999 NV27 | 10.0 | 53.100 | 55.67 | 50.86 | L5 | 15.13 | 0.875 | 1999 | list |
| 4754 Panthoos | 10.0 | 53.025 | 53.15 | 56.96 | L5 | 27.68 | – | 1977 | list |
| 4832 Palinurus | 10.0 | 52.058 | 53.16 | n.a. | L5 | 5.32 | 1.000 | 1988 | list |
| 5126 Achaemenides | 10.5 | 51.922 | 44.22 | 48.57 | L4 | 53.02 | – | 1989 | list |
| 3240 Laocoon | 10.2 | 51.695 | 50.77 | n.a. | L5 | 11.31 | 0.880 | 1978 | list |
| 4902 Thessandrus | 9.8 | 51.263 | 61.04 | 71.79 | L4 | 738 | 0.960 | 1989 | list |
| 11552 Boucolion | 10.1 | 51.136 | 53.16 | 53.91 | L5 | 32.44 | – | 1993 | list |
| (20729) 1999 XS143 | 10.4 | 50.961 | 46.30 | n.a. | L4 | 5.72 | 1.000 | 1999 | list |
| 6545 Leitus | 10.1 | 50.951 | 53.16 | n.a. | L4 | 16.26 | 0.910 | 1986 | list |
| 4792 Lykaon | 10.1 | 50.870 | 53.16 | n.a. | L5 | 40.09 | 0.960 | 1988 | list |
| 21900 Orus | 10.0 | 50.810 | 55.67 | 53.87 | L4 | 13.45 | 0.950 | 1999 | list |
| 1873 Agenor | 10.1 | 50.799 | 53.76 | 54.38 | L5 | 20.60 | – | 1971 | list |
| 5028 Halaesus | 10.2 | 50.770 | 50.77 | n.a. | L4 | 24.94 | 0.900 | 1988 | list |
| 2146 Stentor | 9.9 | 50.755 | 58.29 | n.a. | L4 | 16.40 | – | 1976 | list |
| 4722 Agelaos | 10.0 | 50.378 | 53.16 | 59.47 | L5 | 18.44 | 0.910 | 1977 | list |
| 5284 Orsilocus | 10.1 | 50.159 | 53.16 | n.a. | L4 | 10.31 | 0.970 | 1989 | list |
| 11509 Thersilochos | 10.1 | 49.960 | 53.16 | 56.23 | L5 | 17.37 | – | 1990 | list |
| 5285 Krethon | 10.1 | 49.606 | 58.53 | 52.61 | L4 | 12.04 | 1.090 | 1989 | list |
| 4791 Iphidamas | 10.1 | 49.528 | 57.85 | 59.96 | L5 | 9.70 | 1.030 | 1988 | list |
| 9023 Mnesthus | 10.1 | 49.151 | 50.77 | 60.80 | L5 | 30.66 | – | 1988 | list |
| 5283 Pyrrhus | 9.7 | 48.356 | 64.58 | 69.93 | L4 | 7.32 | 0.950 | 1989 | list |
| 4946 Askalaphus | 10.2 | 48.209 | 52.71 | 66.10 | L4 | 22.73 | 0.940 | 1988 | list |
| (22149) 2000 WD49 | 10.2 | 48.190 | 50.77 | 50.37 | L4 | 7.84 | 1.090 | 2000 | list |
| (32496) 2000 WX182 | 10.2 | 48.017 | 50.77 | 51.63 | L5 | 23.34 | 0.950 | 2000 | list |
| 5120 Bitias | 10.2 | 47.987 | 50.77 | n.a. | L5 | 15.21 | 0.780 | 1988 | list |
| 12714 Alkimos | 10.1 | 47.819 | 61.04 | 54.62 | L4 | 28.48 | – | 1991 | list |
| 7352 Hypsenor | 9.9 | 47.731 | 55.67 | 47.07 | L5 | 648 | 0.850 | 1994 | list |
| 1870 Glaukos | 10.6 | 47.649 | 42.23 | n.a. | L5 | 5.99 | — | 1971 | list |
| 4138 Kalchas | 10.1 | 46.462 | 53.16 | 61.04 | L4 | 29.2 | 0.810 | 1973 | list |
| (23958) 1998 VD30 | 10.2 | 46.001 | 50.77 | 47.91 | L4 | 562 | 0.990 | 1998 | list |
| 4828 Misenus | 10.4 | 45.954 | 46.30 | 43.22 | L5 | 12.87 | 0.920 | 1988 | list |
| 4057 Demophon | 10.1 | 45.683 | 53.16 | n.a. | L4 | 29.82 | 1.060 | 1985 | list |
| 4501 Eurypylos | 10.4 | 45.524 | 46.30 | n.a. | L4 | 6.05 | – | 1989 | list |
| 4007 Euryalos | 10.3 | 45.515 | 48.48 | 53.89 | L4 | 6.39 | – | 1973 | list |
| 5259 Epeigeus | 10.3 | 44.741 | 42.59 | 44.42 | L4 | 18.42 | – | 1989 | list |
| 30705 Idaios | 10.4 | 44.546 | 46.30 | n.a. | L5 | 15.74 | – | 1977 | list |
| 16560 Daitor | 10.7 | 43.861 | 51.42 | 43.38 | L5 | – | – | 1991 | list |
| (15977) 1998 MA11 | 10.4 | 43.530 | 46.30 | 51.53 | L5 | 250 | 0.906 | 1998 | list |
| 7543 Prylis | 10.6 | 42.893 | 42.23 | n.a. | L4 | 17.80 | – | 1973 | list |
| 4827 Dares | 10.5 | 42.770 | 44.22 | n.a. | L5 | 19.00 | – | 1988 | list |
| 1647 Menelaus | 10.5 | 42.716 | 44.22 | n.a. | L4 | 17.74 | 0.866 | 1957 | list |
| $^{(A)}$ Used sources: WISE/NEOWISE catalog (NEOWISE_DIAM_V1 PDS, Grav, 2012); IRAS data (SIMPS v.6 catalog); and Akari catalog (Usui, 2011); RP: rotation period and V–I (color index) taken from the LCDB Note: missing data was completed with figures from the JPL SBDB (query) and from the LCDB (query form) for the WISE/NEOWISE and SIMPS catalogs, respectively. These figures are given in italics. Also, listing is incomplete above #100. ||||||||||

## Naming

This minor planet was named from Greco-Roman mythology after Achates ("fidus Achates"), a close friend and brother-in-arms of the Trojan hero Aeneas in Virgil's Aeneid. After the Trojan War, Achates commanded his own ship in the wandering fleet of Trojans as they sought to establish a new city. Together with Aeneas, he descended into the underworld to find Aeneas' father, Anchises. The official naming citation was published by the Minor Planet Center on 4 June 1993 (M.P.C. 22249).