Callirrhoe (moon)

Not to be confused with Kallichore (moon).

Callirrhoe
This discovery image of Callirrhoe taken by Spacewatch in October 1999
Discovery[1]
Discovered bySpacewatch[a]
Discovery siteKitt Peak National Observatory
Discovery date19 October 1999
Designations
Designation
Jupiter XVII
Pronunciation/kəˈlɪroʊiː/[3][4]
Named after
Καλλιρρόη Kallirrhoê
S/1999 J 1
1999 UX18
Orbital characteristics[5]
Epoch 2026-01-01
Observation arc17.54 yr (6,406 days)
Periapsis15.6 million km
Apoapsis30.9 million km
23.3 million km
Eccentricity0.329
–724.4 days
322°
0° 27m 25.866s / day
Inclination147.3° (to ecliptic)
32.2°
102.2°
Satellite ofJupiter
GroupPasiphae group
Physical characteristics
9.6±1.3 km[6]
Albedo0.052±0.016[6]
Spectral type
D[6]
20.8[7]
13.92±0.02[6]

Callirrhoe (/kəˈlɪroʊ.iː/; Greek: Καλλιρρόη), also known as Jupiter XVII, is one of Jupiter's outermost natural satellites.

Discovery and naming

Callirrhoe was imaged by Spacewatch at Kitt Peak National Observatory from 6 October through 4 November 1999.[8] It was originally believed to be an asteroid, and was thus given the minor planet provisional designation 1999 UX18.[9][10] It was discovered to be in orbit around Jupiter by Tim Spahr on 18 July 2000, and then given the designation S/1999 J 1.[1][11] It was the 17th confirmed moon of Jupiter.[8]

Stack of three images taken by the VLT in July 2000, showing Callirrhoe's movement relative to background stars

It was named in October 2002 after Callirrhoe, daughter of the river god Achelous, one of Zeus's (Jupiter's) many conquests.[12]

Orbit

Callirrhoe orbits Jupiter (at an average distance of 23.3 million km) on a high-eccentricity (0.33) and high-inclination (147° to ecliptic) retrograde orbit.[5] The orbital elements are continuously changing due to solar and planetary perturbations.

It belongs to the Pasiphae group, a group of retrograde moons jupiters with semi-major axes spread over 22–25 million km, inclinations between 141° and 158°, and higher eccentricities between 0.22 and 0.44.

Physical characteristics

Callirrhoe has an apparent magnitude of 20.8,[7] making it even fainter than dwarf planet Eris at magnitude 18.7.[13] Jupiter is about 2.1 billion times brighter than Callirrhoe.[b]

Callirrhoe's measured albedo is around 5.2%, which means its diameter is 9.6 kilometers. [6]

While Pasiphae belongs to the grey color class (V=17.22 B−V=0.74, V−R=0.38), Callirrhoe falls under the light red color class (V=21.39 B−V=0.72, V−R=0.50), similarly to Megaclite and Sinope.[14]

Origin

Callirrhoe probably did not form near Jupiter but was captured by Jupiter later. Callirrhoe is believed to be a fragment from a captured asteroid along with other Pasiphae group satellites.[15][16]

However, it falls into a different color class than Pasiphae and could therefore have been captured by Jupiter independently of the Pasiphae group.

Exploration

Callirrhoe imaged by the LORRI instrument aboard New Horizons

The New Horizons spacecraft flew through the Jovian system in early 2007, using Jupiter for a gravity assist to shorten its journey to Pluto. As a navigation exercise, New Horizons imaged Callirrhoe from a distance on 10 January 2007 using its LORRI instrument.[17]

Notes

  1. ^ The discovery is credited to the team of astronomers consisting of J. V. Scotti, T. B. Spahr, R. S. McMillan, J. A. Larson, J. Montani, A. E. Gleason, and T. Gehrels.[2]
  2. ^

References

  1. ^ a b Brian G. Marsden (20 July 2000). "IAUC 7460: S/1999 J 1". IAU. Archived from the original on 26 April 2006. Retrieved 22 November 2005.
  2. ^ "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology Science Center. Retrieved 26 November 2020.
  3. ^ Noah Webster (1884). A Practical Dictionary of the English Language.
  4. ^ "Pasiphae". Dictionary.com Unabridged (Online). n.d.
  5. ^ a b Horizons output. "Jovian Osculating Orbital Elements for Callirrhoe (517)". Retrieved 18 December 2025.
  6. ^ a b c d e Grav, T.; Bauer, J. M.; Mainzer, A. K.; Masiero, J. R.; Nugent, C. R.; Cutri, R. M.; et al. (August 2015). "NEOWISE: Observations of the Irregular Satellites of Jupiter and Saturn" (PDF). The Astrophysical Journal. 809 (1): 9. Bibcode:2015ApJ...809....3G. doi:10.1088/0004-637X/809/1/3. S2CID 5834661. 3.
  7. ^ a b Sheppard, Scott. "Scott S. Sheppard - Jupiter Moons". Department of Terrestrial Magnetism. Carnegie Institution for Science. Retrieved 26 November 2020.
  8. ^ a b "New Outer Satellite of Jupiter Discovered". Minor Planet Center. Retrieved 23 July 2009.
  9. ^ "New moon of Jupiter found". SpaceFlight Now (University of Arizona News Release). Retrieved 23 July 2009.
  10. ^ MPS 7418 (Minor Planet Circulars Supplement); not available on-line
  11. ^ MPEC 2000-Y16: S/1975 J 1 = S/2000 J 1, S/1999 J 1 2000-12-19 (discovery and ephemeris)
  12. ^ IAUC 7998: Satellites of Jupiter 2002 October 22 (naming the moon)
  13. ^ "AstDys (136199) Eris Ephemerides". Department of Mathematics, University of Pisa, Italy. Retrieved 16 March 2009.
  14. ^ Grav, Tommy; Holman, M. J.; Gladman, B. J.; Aksnes, K. (2003). "Photometric survey of the irregular satellites". Icarus. 166 (1): 33–45. arXiv:astro-ph/0301016. Bibcode:2003Icar..166...33G. doi:10.1016/j.icarus.2003.07.005. S2CID 7793999.
  15. ^ Brown, M. E. (2000). "Near-Infrared Spectroscopy of Centaurs and Irregular Satellites". The Astronomical Journal. 119 (2). The American Astronomical Society: 977–983. Bibcode:2000AJ....119..977B. CiteSeerX 10.1.1.22.1349. doi:10.1086/301202. S2CID 15143844.
  16. ^ Sheppard, S. S.; and Jewitt, D. C.; An Abundant Population of Small Irregular Satellites Around Jupiter Archived 5 August 2003 at the Wayback Machine, Nature, Vol. 423 (May 2003), pp. 261-263
  17. ^ "New Horizons Jupiter Encounter Timeline". www.planetary.org.
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