Ijiraq (moon)

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Ijiraq - Saturn XXII
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 (/ˈjɨrɑːk/ EE-yə-rahk or /ˈɨrɑːk/ EE-jə-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[edit]

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[edit]

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 Ijirap (Ijiraqan) spectrum lacks the weak absorption near 0.7 μm, attributed to a possible water hydration, found in the other three.[4]

Name[edit]

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

References[edit]

  1. Ephemeris from IAU-MPC NSES

External links[edit]