Discovery[1][2] | |
---|---|
Discovered by | Scott S. Sheppard |
Discovery site | Cerro Tololo Obs. |
Discovery date | 11 May 2018 |
Designations | |
Designation | Jupiter LXXI |
Pronunciation | /ˈɜːrsə/ |
Named after | Ἔρσα Ersa |
S/2018 J 1 | |
Orbital characteristics | |
Epoch 1 January 2000 (JD 2451545.0) | |
Observation arc | 21.08 yr (7,701 d) |
Earliest precovery date | 6 August 2000[3] |
Satellite of | Jupiter |
Group | Himalia group |
Proper orbital elements[4] | |
Proper semi-major axis | 11,401,000 km (0.07621 AU) AU |
Proper eccentricity | 0.116 |
Proper inclination | 29.1° (to ecliptic) |
Proper mean motion | 527.587231 deg / yr |
Proper orbital period | 0.68235 yr (249.229 d) |
Precession of perihelion | 8994.503 arcsec / yr |
Precession of the ascending node | 4232.058 arcsec / yr |
Physical characteristics | |
≈3 km[5] | |
Albedo | 0.04 (assumed)[5] |
22.9[5] | |
15.9[1] | |
Ersa /ˈɜːrsə/, also designated Jupiter LXXI, is a small outer natural satellite of Jupiter discovered by Scott S. Sheppard on 11 May 2018, using the 4.0-meter Víctor M. Blanco Telescope at Cerro Tololo Observatory, Chile. It was announced alongside nine other Jovian moons on 17 July 2018 and was provisionally designated S/2018 J 1 by the Minor Planet Center, after observations were collected over a long enough time span to confirm the satellite's orbit.[1] The satellite has been found in precovery observations as early as 6 August 2000.[3]
Ersa is part of the Himalia group, a tight cluster of prograde irregular moons of Jupiter that follow similar orbits to Himalia at semi-major axes between 11–12 million km (6.8–7.5 million mi) and inclinations between 26–31°.[5] With an estimated diameter of 3 km (1.9 mi) for an absolute magnitude of 15.9, it is one of the smallest known members of the Himalia group.[5]
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