15094 Polymele

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15094 Polymele
V–I = 0.799±0.068[10]
11.60[1][3][7][11][12]
11.691±0.002 (S/R)[8]

15094 Polymele

rotation period of 5.9 hours and highly flattened shape.[14][15] It was named after Polymele from Greek mythology, the wife of Menoetius and the mother of Patroclus.[1] In 2022, it was reported to have a natural satellite approximately 5 kilometers (3.1 miles) in diameter.[16]

Orbit and classification

Polymele is a

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.[3] 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 later on.[1]

Naming

This

M.P.C. 98711).[17]

Physical characteristics

Polymele has been characterized as a primitive

V–I color index of 0.799,[10]
which is lower than that for most larger Jupiter trojans (see table below).

Size, shape, and albedo

According to the survey carried out by the

albedo of 0.091,[6][7][11] while in 2018, Marc Buie published an albedo of 0.073 and an absolute magnitude of 11.691 in the S- and/or R band.[8] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a larger diameter of 26.64 kilometers based on an absolute magnitude of 11.6.[12]

On 27 March 2022, multiple astronomers observed a

Kuiper belt object 486958 Arrokoth.[15] This unusual flattened shape of Polymele implies that it had retained its original shape from when it formed by accretion.[15]

Rotation

In March 2016, a rotational

U=2-), which indicates the body is being viewed pole-on.[8] Previously, the Lucy mission team published spin rates of 6.1 and 4 hours, respectively.[9][13]

The resolved observation of Polymele's shape in multiple occultation events allowed the Lucy team to determine the orientation of Polymele's rotational pole.

ecliptic latitude –80.9°, which corresponds to an axial tilt of 170.9° with respect to the ecliptic, making Polymele a retrograde rotator.[5]

Satellite

Discovery of Polymele's satellite in the 26 March 2022 occultation

Following observations of an occultation on 26 March 2022, the Lucy mission team reported the discovery of a natural satellite around Polymele. The satellite is a smaller asteroid about 5–6 kilometers (3.1–3.7 miles) in diameter, orbiting nearly in the equatorial plane of Polymele at a distance of 204.4 ± 2.6 km (127.0 ± 1.6 mi).[14][5] Assuming Polymele has a density of 0.7–1 g/cm3, the satellite should have an orbital period between 14.4 and 16.6 days.[5] It will not be assigned a formal name until further observations determine its orbit.[18] The Lucy team refers to the companion by the temporary informal name "Shaun," after Aardman Animations' animated sheep.[16] The satellite was detected again in an occultation on 4 February 2023,[15] in the largest organized occultation expedition in history. Nearly 200 astronomers across two continents participated in the campaign.[19]

Exploration

Lucy mission target

Polymele is planned to be visited by the Lucy spacecraft which launched in 2021. The flyby is scheduled for 15 September 2027, and will approach the asteroid to a distance of 415 km (258 mi) at a relative velocity of 6 km/s (13,000 mph).[9]

References

  1. ^ a b c d e f g h "15094 Polymele (1999 WB2)". Minor Planet Center. Retrieved 8 March 2018.
  2. ^ 'Polymela' in Noah Webster (1884) A Practical Dictionary of the English Language
  3. ^ a b c d e "JPL Small-Body Database Browser: 15094 Polymele (1999 WB2)" (2015-06-10 last obs.). Jet Propulsion Laboratory. Retrieved 26 September 2018.
  4. ^ "List of Jupiter Trojans". Minor Planet Center. 20 June 2016. Retrieved 8 March 2018.
  5. ^ a b c d e f g h i Levison, H. F.; Buie, M. W.; Keeney, B. A.; Mottola, S.; et al. (June 2023). Interpreting the Stellar Occultations of (15094) Polymele – a Lucy Target (PDF). Asteroids, Comets, Meteors Conference 2023. Lunar and Planetary Institute.
  6. ^
    S2CID 119101711. (online catalog
    )
  7. ^
    Bibcode:2016PDSS..247.....M
    . Retrieved 26 September 2018.
  8. ^
    doi:10.3847/1538-3881/aabd81
    . Retrieved 26 September 2018.
  9. ^
    Bibcode:2017LPI....48.2025L
    . Retrieved 13 April 2017.
  10. ^
    S2CID 54776793
    .
  11. ^
    S2CID 118700974. (catalog
    )
  12. ^ a b "LCDB Data for (15094) Polymele". Asteroid Lightcurve Database (LCDB). Retrieved 26 September 2018.
  13. ^
    Bibcode:2016DPS....4820806B
    .
  14. ^
    Bibcode:2022DPS....5451203B
    . 512.03. Retrieved 28 January 2023.
  15. ^ a b c d Buie, M. W.; Keeney, B. A.; Levison, H. F.; et al. (June 2023). Occultation results for the (15094) Polymele system – a Lucy Target (PDF). Asteroids, Comets, Meteors Conference 2023. Lunar and Planetary Institute.
  16. ^ a b Clark, Stephen (14 June 2022). "Ninth asteroid added to Lucy mission; optimism grows on solar array issue". Spaceflight Now. Retrieved 15 June 2022.
  17. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 8 March 2018.
  18. ^ "NASA's Lucy Team Discovers Moon Around Asteroid Polymele". NASA. 16 August 2022. Retrieved 17 August 2022.
  19. ^ NASA/SwRI. "Spotting a Satellite - Lucy Mission". LUCY Mission Page. Retrieved 1 September 2023.

External links

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