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Hyrrokkin (// hi-ROK-in) or Saturn XLIV (provisional designation S/2004 S 19) is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on June 26, 2006, from observations taken between December 12, 2004, and April 30, 2006.
Hyrrokkin is about 8 kilometres in diameter, and orbits Saturn at an average distance of 18,168 Mm in 914 days, at an inclination of 153° to the ecliptic (154° to Saturn's equator), in a retrograde direction and with an eccentricity of 0.36. During four observations in March 2013, the synodic rotational period was measured by the Cassini spacecraft to approximately 12 hours and 45 minutes.
It was named in April 2007 after Hyrrokkin, a giantess from Norse mythology, who launched Hringhorni, Baldr's funeral ship. It was originally listed as being spelled Hyrokkin, but the spelling was later corrected.
- Rehnberg, Morgan (14 August 2015). "Cassini studies backwards-orbiting moon Hyrrokkin". Space Exploration Network. SEN. Retrieved 2015-08-17.
- Scott Sheppard's Saturnian satellites page
- IAUC 8727: Satellites of Saturn June 30, 2006 (discovery)
- MPEC 2006-M44: S/2004 S 19 June 26, 2006 (discovery and ephemeris)
- IAUC 8826: Satellites of Jupiter and Saturn April 5, 2007 (Naming the moon)
- IAUC 8860: Saturn XLIV (Hyrrokkin) July 31, 2007 (correcting the name)
- Denk, T., Mottola, S. (2013): Irregular Saturnian Moon Lightcurves from Cassini-ISS Observations: Update. Abstract 406.08, DPS conference 2013, Denver (Colorado), October 10, 2013 (synodic rotation period)