Discovery

Ijiraq was discovered on Sept. 23, 2000 by Brett J. Gladman, John J. Kavelaars, Jean-Marc Petit, Hans Scholl, Matthew J. Holman, Brian G. Marsden, Phillip D. Nicholson, and Joseph A. Burns using the 3.6-m Canada-France-Hawaii reflector on Mauna Kea, Hawaii, with adaptive optics. They discovered seven other Saturnian moons at the same time: Siarnaq, Tarvos, Thrymr, Skathi, Mundilfari, Erriapus, and Suttungr.

Overview

Ijiraq has a mean radius of 3.7 miles (6 kilometers), assuming an albedo (a measure of how reflective the surface is) of 0.06. At a mean distance of 7.1 million miles (11.4 million kilometers) from Saturn, the moon takes about 452 Earth days to complete one orbit.

Ijiraq is one of five known members of the Inuit group of moons, which orbit Saturn at a mean distance of 7 to 11 million miles (11 to 18 million kilometers, at inclinations between 40 and 50 degrees from the plane of Saturn's equator, and with eccentricities of 0.15 to 0.48. (A moon's eccentricity is a number between 0 and 1 which describes the shape of the orbit. The closer to 0, the more circular it is; the closer to 1, the more elongated.)

The Inuit moons all have prograde orbits (they travel around Saturn in the same direction as the planet's rotation), but their deviations from circular orbits and from the plane of Saturn's equator classify them as "irregular" moons. Like Saturn's other irregular moons, they are thought to be objects that were captured by Saturn's gravity, rather than having accreted from the dusty disk that surrounded the newly formed planet, as the regular moons are thought to have done.

The similarities among the Inuit group's orbits suggest a common origin -- they may be fragments of a single object that shattered in a collision. The other members of this group are Kiviuq, Paaliaq, Siarnaq, and Tarqeq.

Observations by Tommy Grav and James Bauer using telescopes on Mauna Kea, Hawaii in 2006 (before the discovery of Tarqeq) found that Ijiraq is redder than Kiviuq, Siarnaq and Paaliaq, and lacks the feature these other moons display at the deep red wavelength of 0.7 micrometers.

How Ijiraq Got its Name

Originally called S/2000 S6, Ijiraq was named for a fictional character in the children's book, "Hide and Sneak" by Michael Arvaarluk Kusugak. The moon's co-discoverer, John J. Kavelaars, was reading the book to his children when he was struck by the realization that the character, who helped children hide, would provide a fitting namesake for one of Saturn's elusive moons.

Author Kusugak is responsible for the names of four of the five known moons in the Inuit group. He co-wrote the book from which the name Paaliaq was taken, and he suggested the names Kiviuq and Siarnaq, which came from Inuit legend and mythology.

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