Ijiraq (moon)

Ijiraq

Animated discovery image of Ijiraq
Discovery[1]
Discovered by	J. J. Kavelaars B. J. Gladman
Discovered	in 2000
Mean Orbital elements[2]
Epoch 2000 Feb. 26.00
Semi-major axis	11.124 Gm
Eccentricity	0.3163
Inclination	46.444° ^*
Orbital period	451.4 d (1.24 yr)
Physical characteristics
Mean diameter	12 km[3] ^**
Rotation period	?
Albedo	0.04[3] assumed
Color	red B-V=1.05 R-V=0.58[4]
Spectral type	(redder than D)[4]
^*to the ecliptic ^**based on the albedo

Ijiraq (/ˈiːjᵻrɑːk/ EE-yə-rahk or /ˈɪdʒᵻrɑːk/ IJ-ə-rahk), or Saturn XXII (22), is 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.^[5][6] 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 11.1 Gm in 451 days on an orbit very similar to Kiviuq's. 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]

Physical characteristics

Animated discovery image of Ijiraq 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) spectrum lacks the weak absorption near 0.7 μm, attributed to a possible water hydration, found in the other three.^[4]

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.

References

1. Discovery Circumstances (JPL)
2. Mean orbital parameters from JPL
3. Scott Sheppard pages
4. Grav, T.; and Bauer, J.; A deeper look at the colors of Saturnian irregular satellites
5. IAUC 7521: S/2000 S 5, S/2000 S 6 November 18, 2000 (discovery)
6. MPEC 2000-Y14: S/2000 S 3, S/2000 S 4, S/2000 S 5, S/2000 S 6, S/2000 S 10 December 19, 2000 (discovery and ephemeris)
7. IAUC 8177: Satellites of Jupiter, Saturn, Uranus August 8, 2003 (naming the moon)
8. Nesvorný, D.; Alvarellos, Jose L. A.; Dones, L.; and Levison, H. F.; Orbital and Collisional Evolution of the Irregular Satellites, The Astronomical Journal, 126 (2003), pp. 398–429
9. Gladman, B. J.; Nicholson, P. D.; Burns, J. A.; Kavelaars, J. J.; Marsden, B. G.; Holman, M. J.; Grav, T.; Hergenrother, C. W.; Petit, J.-M.; Jacobson, R. A.; and Gray, W. J.; Discovery of 12 satellites of Saturn exhibiting orbital clustering, Nature, 412 (July 12, 2001), pp. 163–166

10. Ephemeris from IAU-MPC NSES

External links

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