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
Pronunciation /ˌpɒlɪˈmli/
Named after
(Greek mythology)[2]
1999 WB2 · 1997 WR57
Jupiter trojan[1][2]
(Greek camp)[3]
Orbital characteristics[1]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc 24.10 yr (8,803 d)
Aphelion 5.6537 AU
Perihelion 4.6781 AU
5.1659 AU
Eccentricity 0.0944
11.74 yr (4,289 d)
0° 5m 2.04s / day
Inclination 12.990°
Jupiter MOID 0.2252 AU
TJupiter 2.9400
Physical characteristics
Dimensions 21.075±0.136 km[4]
6.1 h[6]

15094 Polymele (/ˌpɒlɪˈmli/), provisional designation 1999 WB2, is a primitive Jupiter trojan from the Greek camp, approximately 21 kilometers (13 miles) 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, the wife of Menoetius and the mother of Patroclus in 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 (4,289 days; semi-major axis of 5.17 AU). 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 taken at Palomar Observatory in 1951, and published by the Digitized Sky Survey.[2]

Physical characteristics[edit]

Polymele has been characterized as a primitive P-type asteroid by the investigators of the Lucy mission.[6] P-type asteroids are known for their low albedo.

Diameter and albedo[edit]

According to the survey carried out by 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] It has not been observed previously, neither by the Infrared Astronomical Satellite IRAS, nor by the Japanese Akari satellite.


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 2018, 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]

  • 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.


  1. ^ a b c d e "JPL Small-Body Database Browser: 15094 Polymele (1999 WB2)" (2015-06-10 last obs.). Jet Propulsion Laboratory. Retrieved 8 March 2018. 
  2. ^ a b c d e "15094 Polymele (1999 WB2)". Minor Planet Center. Retrieved 8 March 2018. 
  3. ^ "List of Jupiter Trojans". Minor Planet Center. 20 June 2016. Retrieved 8 March 2018. 
  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" (PDF). 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 8 March 2018. 
  8. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 8 March 2018. 
  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]