Discovery [1] | |
---|---|
Discovered by | Catalina Sky Survey |
Discovery site | Catalina Station |
Discovery date | 17 November 1999 |
Designations | |
(15094) Polymele | |
Pronunciation | /pɒlɪˈmiːliː/ [2] |
Named after |
Polymele ( Greek mythology) [1] |
1999 WB2 · 1997 WR57 | |
Jupiter trojan
[1]
[3] ( Greek camp) [4] | |
Orbital characteristics [3] | |
Epoch 25 February 2023 ( JD 2460000.5) | |
Uncertainty parameter 0 | |
Earliest precovery date | 30 November 1951 [1] |
Aphelion | 5.682 AU |
Perihelion | 4.679 AU |
5.180 AU | |
Eccentricity | 0.0968 |
11.79 yr (4,307 d) | |
44.314 ° | |
0° 5m 0.936s / day | |
Inclination | 12.981° |
50.319° | |
4.772° | |
Jupiter MOID | 0.2445 AU |
TJupiter | 2.940 |
Physical characteristics | |
Dimensions | 27.0 × 24.4 × 10.4 km
[5] (± 2.0 × 1.6 × 1.6 km) |
21.075±0.136 km [6] [7] | |
Mean
density | 0.7–1 g/cm3 (assumed) [5] |
5.8607±0.0005 h [8] | |
170.9° (wrt ecliptic) [5] | |
Pole
ecliptic latitude | −80.9°±2.1° [5] |
Pole
ecliptic longitude | 231.8°±4.5° [5] |
0.073
[8] 0.091±0.017 [3] | |
P
[9] B–V = 0.652±0.065 [10] V–R = 0.477±0.065 [10] V–I = 0.799±0.068 [10] | |
11.60
[1]
[3]
[7]
[11]
[12] 11.691±0.002 (S/R) [8] | |
15094 Polymele /pɒlɪˈmiːliː/ 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 flyby planned to occur in September 2027. [9] [13] It was discovered on 17 November 1999, by astronomers with the Catalina Sky Survey at Mount Lemmon Observatory, Arizona, in the United States. The P-type asteroid has a 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]
Polymele is a Jupiter trojan 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. [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]
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. [1] 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). [17]
Polymele has been characterized as a primitive P-type asteroid by the investigators of the Lucy mission. [9] P-type asteroids are known for their low albedo. It has a V–I color index of 0.799, [10] which is lower than that for most larger Jupiter trojans (see table below).
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Polymele measures 21.075 kilometers in diameter and its surface has an 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 stellar occultation by Polymele, which revealed an apparently elongated projected shape with projected dimensions of 26.2 km × 12.8 km (16.3 mi × 8.0 mi). [14] Additional occultation observations of Polymele from 2020–2023 revealed that Polymele's true shape is a highly flattened disk with dimensions 27.0 km × 24.4 km × 10.4 km (16.8 mi × 15.2 mi × 6.5 mi), similar to the large flat lobe of the 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]
In March 2016, a rotational lightcurve of Polymele was obtained from photometric observations by Marc Buie and colleges. Lightcurve analysis gave a rotation period of 5.8607±0.0005 hours with a small brightness amplitude of 0.09±0.03 magnitude ( 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. [5] Polymele's rotational north pole points toward ecliptic latitude –80.9°, which corresponds to an axial tilt of 170.9° with respect to the ecliptic, making Polymele a retrograde rotator. [5]
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]
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]
Discovery [1] | |
---|---|
Discovered by | Catalina Sky Survey |
Discovery site | Catalina Station |
Discovery date | 17 November 1999 |
Designations | |
(15094) Polymele | |
Pronunciation | /pɒlɪˈmiːliː/ [2] |
Named after |
Polymele ( Greek mythology) [1] |
1999 WB2 · 1997 WR57 | |
Jupiter trojan
[1]
[3] ( Greek camp) [4] | |
Orbital characteristics [3] | |
Epoch 25 February 2023 ( JD 2460000.5) | |
Uncertainty parameter 0 | |
Earliest precovery date | 30 November 1951 [1] |
Aphelion | 5.682 AU |
Perihelion | 4.679 AU |
5.180 AU | |
Eccentricity | 0.0968 |
11.79 yr (4,307 d) | |
44.314 ° | |
0° 5m 0.936s / day | |
Inclination | 12.981° |
50.319° | |
4.772° | |
Jupiter MOID | 0.2445 AU |
TJupiter | 2.940 |
Physical characteristics | |
Dimensions | 27.0 × 24.4 × 10.4 km
[5] (± 2.0 × 1.6 × 1.6 km) |
21.075±0.136 km [6] [7] | |
Mean
density | 0.7–1 g/cm3 (assumed) [5] |
5.8607±0.0005 h [8] | |
170.9° (wrt ecliptic) [5] | |
Pole
ecliptic latitude | −80.9°±2.1° [5] |
Pole
ecliptic longitude | 231.8°±4.5° [5] |
0.073
[8] 0.091±0.017 [3] | |
P
[9] B–V = 0.652±0.065 [10] V–R = 0.477±0.065 [10] V–I = 0.799±0.068 [10] | |
11.60
[1]
[3]
[7]
[11]
[12] 11.691±0.002 (S/R) [8] | |
15094 Polymele /pɒlɪˈmiːliː/ 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 flyby planned to occur in September 2027. [9] [13] It was discovered on 17 November 1999, by astronomers with the Catalina Sky Survey at Mount Lemmon Observatory, Arizona, in the United States. The P-type asteroid has a 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]
Polymele is a Jupiter trojan 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. [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]
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. [1] 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). [17]
Polymele has been characterized as a primitive P-type asteroid by the investigators of the Lucy mission. [9] P-type asteroids are known for their low albedo. It has a V–I color index of 0.799, [10] which is lower than that for most larger Jupiter trojans (see table below).
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Polymele measures 21.075 kilometers in diameter and its surface has an 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 stellar occultation by Polymele, which revealed an apparently elongated projected shape with projected dimensions of 26.2 km × 12.8 km (16.3 mi × 8.0 mi). [14] Additional occultation observations of Polymele from 2020–2023 revealed that Polymele's true shape is a highly flattened disk with dimensions 27.0 km × 24.4 km × 10.4 km (16.8 mi × 15.2 mi × 6.5 mi), similar to the large flat lobe of the 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]
In March 2016, a rotational lightcurve of Polymele was obtained from photometric observations by Marc Buie and colleges. Lightcurve analysis gave a rotation period of 5.8607±0.0005 hours with a small brightness amplitude of 0.09±0.03 magnitude ( 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. [5] Polymele's rotational north pole points toward ecliptic latitude –80.9°, which corresponds to an axial tilt of 170.9° with respect to the ecliptic, making Polymele a retrograde rotator. [5]
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]
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]