|Discovery site||Beijing Xinglong Obs.|
|Discovery date||12 October 1997|
|MPC designation||(11351) Leucus|
|Pronunciation||// · LEEW-kəs|
|Leucus (Greek mythology)|
|1997 TS25 · 1996 VP39|
Jupiter trojan |
Greek  · background 
|Orbital characteristics |
|Epoch 23 March 2018 (JD 2458200.5)|
|Uncertainty parameter 0|
|Observation arc||20.57 yr (7,515 d)|
|12.16 yr (4,440 d)|
|0° 4m 51.96s / day|
|Jupiter MOID||0.1005 AU|
B–V = ±0.0440.739
V–R = ±0.0440.498
V–I = ±0.0570.900
11351 Leucus (// LEEW-kəs), provisional designation 1997 TS25, is a mid-sized Jupiter trojan from the Greek camp, approximately 40 kilometers (25 miles) in diameter. It is a target of the Lucy mission, scheduled for a fly by in April 2028. The assumed D-type asteroid is an exceptionally slow rotator with a rotation period of 515 hours. It was discovered on 12 October 1997 by the Beijing Schmidt CCD Asteroid Program (SCAP) at Xinglong Station in the Chinese province of Hebei, and later named after the Achaean warrior Leucus from Greek mythology.
Orbit and classification
Leucus is a dark Jovian asteroid in a 1:1 orbital resonance with Jupiter. It is located in the leading Greek camp at the Gas Giant's L4 Lagrangian point, 60° ahead of its orbit . It is also a non-family asteroid in the Jovian background population.
It orbits the Sun at a distance of 5.0–5.6 AU once every 12 years and 2 months (4,440 days; semi-major axis of 5.29 AU). Its orbit has an eccentricity of 0.06 and an inclination of 12° with respect to the ecliptic. The body's observation arc begins with a precovery taken at the Siding Spring Observatory in July 1982, more than 15 years prior to its official discovery observation at Xinglong.
Lucy mission target
Leucus is planned to be visited by the Lucy spacecraft which will launch in 2021. The fly by is scheduled for 18 April 2028, and will approach the asteroid to a distance of 1000 kilometers at a velocity of 5.9 kilometers per second. The mission's targets with their flyby dates are:
- 52246 Donaldjohanson — 20 April 2025: 4 km diameter C-type asteroid in the inner main-belt, member of ~130Myr old Erigone family;
- 3548 Eurybates — 12 August 2027: 64 km diameter C-type Jupiter Trojan in the Greek camp at L4, largest member of the only confirmed disruptive collisional family in the Trojans;
- 15094 Polymele — 15 September 2027: 21 km diameter P-type Trojan at L4, likely collisional fragment;
- 11351 Leucus — 18 April 2028: 34 km diameter D-type slow rotator Trojan at L4;
- 21900 Orus — 11 November 2028: 51 km diameter D-type Trojan at L4;
- 617 Patroclus — 2 March 2033: P-type binary Trojan. The primary, Patroclus, has a mean diameter of 113 km and its companion, Menoetius, has a diameter of 104 km. The pair orbit at a separation of 680 km. The binary resides in the Trojan camp at L5.
During spring 2013, a rotational lightcurve of Leucus was obtained from photometric observations made by astronomers Robert Stephens and Daniel Coley at the Center for Solar System Studies (CS3), California, using a 0.35/0.4-meter Schmidt-Cassegrain telescope. The lightcurve showed an exceptionally slow rotation period of 513.7 hours with a brightness variation of 0.53 in magnitude (U=2+). No evidence of a non-principal axis rotation (NPAR) was found.[a] It is one of the slowest rotators known to exist.
In preparation for the planned visit by the Lucy spacecraft, Leucus was once again observed by astronomers Marc Buie at SwRI and Stefano Mottola at DLR in 2016. The obtained bimodal lightcurve gave a somewhat shorter period of 440 hours and an amplitude of 0.7 magnitude.
Diameter and albedo
According to the surveys carried out by the Infrared Astronomical Satellite IRAS, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Leucus has a low albedo of 0.06 and 0.08, with a diameter of 42.1 and 34.2 kilometers, respectively. The Collaborative Asteroid Lightcurve Link derives a lower albedo of 0.05 and a diameter of 42.1 kilometers, in accordance with the result obtained by IRAS.
This minor planet was named from Greek mythology, after the Achaean warrior Leucus in Homer's Iliad. He was a companion of Odysseus. Leucus was killed during the Trojan War by Antiphus, one of the fifty sons of King Priam of Troy. The approved naming citation was published by the Minor Planet Center on 22 February 2016 (M.P.C. 98711).
- "11351 Leucus (1997 TS25)". Minor Planet Center. Retrieved 22 June 2018.
- "JPL Small-Body Database Browser: 11351 Leucus (1997 TS25)" (2017-06-07 last obs.). Jet Propulsion Laboratory. Retrieved 22 June 2018.
- "List of Jupiter Trojans". Minor Planet Center. 1 June 2018. Retrieved 22 June 2018.
- "Asteroid (11351) Leucus – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 22 June 2018.
- Grav, T.; Mainzer, A. K.; Bauer, J. M.; Masiero, J. R.; Nugent, C. R. (November 2012). "WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy". The Astrophysical Journal. 759 (1): 10. arXiv: . Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. Retrieved 22 June 2018. (online catalog)
- Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System – IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 15 June 2018.
- French, Linda M.; Stephens, Robert, D.; Coley, Daniel R.; Wasserman, Lawrence H.; Vilas, Faith; La Rocca, Daniel (October 2013). "A Troop of Trojans: Photometry of 24 Jovian Trojan Asteroids". The Minor Planet Bulletin. 40 (4): 198–203. Bibcode:2013MPBu...40..198F. ISSN 1052-8091. Retrieved 22 June 2018.
- Levison, H. F.; Olkin, C.; Noll, K. S.; Marchi, S.; Lucy Team (March 2017). "Lucy: Surveying the Diversity of the Trojan Asteroids: The Fossils of Planet Formation" (PDF). 48th Lunar and Planetary Science Conference. Bibcode:2017LPI....48.2025L. Retrieved 13 April 2017.
- Hainaut, O. R.; Boehnhardt, H.; Protopapa, S. (October 2012). "Colours of minor bodies in the outer solar system. II. A statistical analysis revisited" (PDF). Astronomy and Astrophysics. 546: 20. arXiv: . Bibcode:2012A&A...546A.115H. doi:10.1051/0004-6361/201219566. Retrieved 22 June 2018.
- "LCDB Data for (11351) Leucus". Asteroid Lightcurve Database (LCDB). Retrieved 22 June 2018.
- Casey Dreier; Emily Lakdawalla (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society. Retrieved 12 April 2017.
- Buie, Marc W.; Zangari, Amanda Marie; Marchi, Simone; Mottola, Stefano; Levison, Harold F. (October 2016). "Ground-based characterization of Leucus and Polymele, two fly-by targets of the Lucy Discovery mission". American Astronomical Society. Bibcode:2016DPS....4820806B. Retrieved 13 April 2017.
- Homer, Iliad, 4. 491
- "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 22 June 2018.
- Asteroid Lightcurve Database (LCDB), query form (info)
- Dictionary of Minor Planet Names, Google books
- Discovery Circumstances: Numbered Minor Planets (10001)-(15000) – Minor Planet Center
- Asteroid 11351 Leucus at the Small Bodies Data Ferret
- 11351 Leucus at AstDyS-2, Asteroids—Dynamic Site
- 11351 Leucus at the JPL Small-Body Database