Ijiraq (moon)

Ijiraq

Discovery images of Ijiraq taken by the CFHT in September 2000
Discovery[1][2]
Discovered by	J. J. Kavelaars B. J. Gladman
Discovery date	2000
Designations
Designation	Saturn XXII
Pronunciation	/ˈɪdʒɪrɑːk/
Named after	Ijiraq
Alternative names	S/2000 S 6
Adjectives	Ijiraupian, Ijiraqian[a]
Orbital characteristics[3]
Epoch 2000 January 1.5
Semi-major axis	11.345 Gm
Eccentricity	0.353
Orbital period (sidereal)	451.46 d (1.24 yr)
Inclination	49.2°
Satellite of	Saturn
Group	Inuit group (Kiviuq)
Physical characteristics[4][5]
Mean diameter	13+50% −30% km
Synodic rotation period	13.03±0.14 h
Albedo	0.06 assumed
Spectral type	color: red B-V=1.05 R-V=0.58[6]
Apparent magnitude	22.6
Absolute magnitude (H)	13.2

Ijiraq, or Saturn XXII (22), is a small prograde irregular satellite of Saturn. It was discovered by the team of Brett Gladman, John J. Kavelaars, et al. in 2000, and given the temporary designation S/2000 S 6.^[1][2] It was named in 2003 after the ijiraq, a creature in Inuit mythology.^[7]

Orbit

Irregular prograde groups of satellites of Saturn: Inuit (blue) and Gallic (red). The eccentricity of the orbits is represented by the yellow segments extending from the pericentre to the apocentre.

Ijiraq orbits Saturn at an average distance of 11.3 million km in 451 days on an orbit very similar to Kiviuq's.^[3] Ijiraq is believed to be in Kozai resonance: its orbit is cyclically reducing the inclination while increasing the eccentricity and vice versa. The orbital argument of pericenter oscillates around 90° with an amplitude of 60°.^[8] Like Kiviuq and Thrymr, Ijiraq's orbital elements overlap strongly with Phoebe's, and it is likely to collide with Phoebe in the future.^[5]

Physical characteristics

While Ijiraq is a member of the Inuit group of irregular satellites,^[9] recent observations revealed that it is distinctively redder than Paaliaq, Siarnaq and Kiviuq. Its spectral slope (a measure of body reflectance in function of the wavelength) is twice as steep as that of other Inuit-group satellites (20% per 100 nm), typical for red trans-Neptunian objects like Sedna but unknown for irregular satellites. In addition, the Ijiraupian (Ijiraqan)^[a] spectrum lacks the weak absorption near 0.7 μm, attributed to a possible water hydration, found in the other three.^[6]

Name

Ijiraq was named in 2003 after the ijiraq, a creature of Inuit mythology.^[7]

Kavelaars, an astronomer at McMaster University, suggested this name to help astronomical nomenclature to get out of its Greco-Romano-Renaissance rut. He spent several months trying to find names that were both multi-cultural and Canadian, consulting Amerindian scholars without finding a name that seemed appropriate. In March 2001, he was reading an Inuit tale to his children and had a revelation. The ijiraq plays at hide-and-seek, which is what these small moons of Saturn do: they are hard to find, and cold like the Canadian arctic (the team of discoverers includes Canadians, Norwegians and Icelanders—nordicity is their common trait). Kavelaars contacted the author of the tale, Michael Kusugak, to get his assent, and the latter also suggested the names for Kiviuq and 90377 Sedna.

Notes

1. The genitive form of Ijiraq is Ijiraup. Thus the adjectival form could be absolutive Ijiraqian or genitive Ijiraupian, parallel to nominative Venusian and genitive Venerian for Venus. See Inuktitut morphology

References

1. "IAUC 7521: S/2000 S 5, S/2000 S 6". www.cbat.eps.harvard.edu. November 18, 2000.
2. "MPEC 2000-Y14 : S/2000 S 3, S/2000 S 4, S/2000 S 5, S/2000 S 6, S/2000 S 10". minorplanetcenter.net. December 19, 2000.
3. "Planetary Satellite Mean Elements". ssd.jpl.nasa.gov.
4. Denk, T.; Mottola, S. (2019). Cassini Observations of Saturn's Irregular Moons (PDF). 50th Lunar and Planetary Science Conference. Lunar and Planetary Institute.
5. Denk, Tilmann; Mottola, Stefano; Tosi, Frederico; Bottke, William F.; Hamilton, Douglas P. (2018). "The Irregular Satellites of Saturn" (PDF). In Schenk, P.M.; Clark, R.N.; Howett, C.J.A.; Verbiscer, A.J.; Waite, J.H. (eds.). Enceladus and the Icy Moons of Saturn. Space Science Series. Vol. 322. Tucson, AZ: The University of Arizona Press. pp. 409–434. Bibcode:2018eims.book..409D. doi:10.2458/azu_uapress_9780816537075-ch020. ISBN 9780816537075.
6. Grav, T.; Bauer, J. (2007-03-08) [2006-11-18]. "A deeper look at the colors of the Saturnian irregular satellites". Icarus. 191 (1): 267–285. arXiv:astro-ph/0611590. Bibcode:2007Icar..191..267G. doi:10.1016/j.icarus.2007.04.020. S2CID 15710195.
7. "IAUC 8177: Sats OF (22); Sats OF JUPITER, SATURN, URANUS". www.cbat.eps.harvard.edu. August 8, 2003.
8. Nesvorn, David; Alvarellos, Jose L. A.; Dones, Luke; Levison, Harold F. (2003). "Orbital and Collisional Evolution of the Irregular Satellites". The Astronomical Journal. 126 (1). IOP Publishing: 425. Bibcode:2003AJ....126..398N. doi:10.1086/375461.
9. Gladman, Brett; Kavelaars, J. J.; Holman, Matthew; Nicholson, Philip D.; Burns, Joseph A.; Hergenrother, Carl W.; Petit, Jean-Marc; Marsden, Brian G.; Jacobson, Robert; Gray, William; Grav, Tommy (2001-07-12). "Discovery of 12 satellites of Saturn exhibiting orbital clustering". Nature. 412 (6843): 163–166. Bibcode:2001Natur.412..163G. doi:10.1038/35084032. ISSN 1476-4687. PMID 11449267. S2CID 4420031.

External links

• Ephemeris from IAU-MPC NSES