15094 Polymele

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15094 Polymele
Discovery [1]
Discovered by CSS
Discovery site Mount Lemmon Obs.
Discovery date 17 November 1999
MPC designation (15094) Polymele
Named after
(Greek mythology)[2]
1999 WB2 · 1997 WR57
Jupiter trojan[1][2]
(Greek camp)[3]
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc 24.10 yr (8,803 days)
Aphelion 5.6519 AU
Perihelion 4.6769 AU
5.1644 AU
Eccentricity 0.0944
11.74 yr (4,287 days)
0° 5m 2.4s / day
Inclination 12.992°
Jupiter MOID 0.2223 AU
Jupiter Tisserand parameter 2.9400
Physical characteristics
Dimensions 21.075±0.136 km[4]
4 h[5]
6.1 h[6]

15094 Polymele, provisional designation 1999 WB2, is a dark Jupiter trojan from the Greek camp, approximately 21 kilometers in diameter. It is a target of the Lucy mission with a close fly by planned to occur in September 2027.[5][6]

It was discovered on 17 November 1999, by astronomers of the Catalina Sky Survey at Mount Lemmon Observatory, Arizona, United States, and later named after Polymele, a figure from Greek mythology.[2]

Orbit and classification[edit]

Polymele is a Jovian asteroid orbiting in the leading Greek camp at Jupiter's L4 Lagrangian point, 60° ahead of the Gas Giant's orbit (see Trojans in astronomy). It orbits the Sun at a distance of 4.7–5.7 AU once every 11 years and 9 months (4,287 days). Its orbit has an eccentricity of 0.09 and an inclination of 13° with respect to the ecliptic.[1]

The asteroid's observation arc begins 48 years prior to its official discovery observation at Mount Lemmon, with a precovery from the Digitized Sky Survey, taken at Palomar Observatory in 1951.[2]

Physical characteristics[edit]

Polymele has been characterized as a dark and uncommon P-type asteroid by the investigators of the Lucy mission.[6] They are known for their low albedos.

Diameter and albedo[edit]

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Polymele measures 21.075 kilometers in diameter and its surface has an albedo of 0.091.[4]


In 2016, photometric observations of Polymele give a rotation period of approximately 4 hours with a low brightness variation of 0.1 magnitude (U=n.a.), which indicates that the body has a spheroidal shape.[5] The Lucy mission team, however, publishes a spin rate of 6.1 hours in their fact-sheet.[6] As of April 2017, Polymele in not yet listed in the Lightcurve Data Base.[7]


This minor planet was named after Polymele, the daughter of Peleus from Greek mythology. According to the Latin author Gaius Julius Hyginus (c. 64 BC – AD 17), she is the wife of the Argonaut Menoetius and the mother of Patroclus, who participated in the Trojan War.[2] Polymele is also known as "Philomela"; that name was previously used for the asteroid 196 Philomela. The approved naming citation was published by the Minor Planet Center on 22 February 2016 (M.P.C. 98711).[8]

Lucy mission target[edit]

Polymele is planned to be visited by the Lucy spacecraft which will launch in 2021. The fly by is scheduled for 15 September 2027, and will approach the asteroid to a distance of 415 kilometers at a velocity of 6 kilometers per second.[6] The mission's targets with their flyby dates are:[6][9][10]

  1. 52246 Donaldjohanson — 20 April 2025: 4 km diameter C-type asteroid in the inner main-belt, member of ~130Myr old Erigone family;
  2. 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;
  3. 15094 Polymele — 15 September 2027: 21 km diameter P-type Trojan at L4, likely collisional fragment;
  4. 11351 Leucus — 18 April 2028: 34 km diameter D-type slow rotator Trojan at L4;
  5. 21900 Orus — 11 November 2028: 51 km diameter D-type Trojan at L4;
  6. 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.


  1. ^ a b c d e "JPL Small-Body Database Browser: 15094 Polymele (1999 WB2)" (2015-06-10 last obs.). Jet Propulsion Laboratory. Retrieved 5 July 2017. 
  2. ^ a b c d e "15094 Polymele (1999 WB2)". Minor Planet Center. Retrieved 12 April 2017. 
  3. ^ "List of Jupiter Trojans". Minor Planet Center. 20 June 2016. Retrieved 4 December 2016. 
  4. ^ a b c 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:1209.1549Freely accessible. Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. Retrieved 12 April 2017. 
  5. ^ a b c 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. 
  6. ^ a b c d e f g 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. 
  7. ^ "LCDB Data for (15094) Polymele". Asteroid Lightcurve Database (LCDB). Retrieved 12 April 2017. 
  8. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 12 April 2017. 
  9. ^ Casey Dreier; Emily Lakdawalla (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society. Retrieved 12 April 2017. 
  10. ^ https://www.hou.usra.edu/meetings/lpsc2017/pdf/2025.pdf

External links[edit]