page_title: Siarnaq
section_title: Discovery
hierarchical_section_title: Siarnaq / History / Discovery
caption_attribution_description: English: Animation of three discovery images of Saturn's irregular moon Siarnaq (S/2000 S 3), taken by the 3.6-meter Canada-France-Hawaii Telescope (CFHT) on 23 September 2000. Each image was taken approximately 90 minutes apart, showing the moon's motion relative to the background stars and galaxies. The raw image datasets used are 550459p, 550469p, and 550481p. For comparison, the star field in these images can be viewed at the CDS's Aladin star atlas.
context_page_description: Siarnaq, also designated Saturn XXIX, is a prograde irregular satellite of Saturn. It was discovered at the Mauna Kea Observatory by astronomers Brett Gladman and John Kavelaars in 2000, and given the temporary designation S/2000 S 3. Named after Siarnaq, the Inuit goddess of the sea, it is the largest member of the Inuit group of irregular satellites.
context_section_description: Siarnaq was discovered by Canadian astronomers Brett Gladman and John Kavelaars at the Mauna Kea Observatory on 23 September 2000. The discovery of Siarnaq formed part of an observational campaign, coordinated by Gladman in late 2000, to search for distant irregular satellites around Saturn. The campaign consisted of an international team of eight astronomers using various ground-based telescopes to survey Saturn's Hill sphere, the region within which satellites can have stable orbits around the planet. The first campaign observations were conducted in August 2000 and produced two irregular satellite candidates: Ymir and Paaliaq. However, with a limited set of observations, their orbits were indeterminate and required further observations before announcing their discoveries.
  On 23 September 2000, a more extensive search for irregular satellites was conducted by Gladman and Kavelaars using the 3.6-meter Canada-France-Hawaii Telescope (CFHT) at the Mauna Kea Observatory in Hawaii. With a wide field of view along with a digital charge-coupled device camera, the CFHT covered a larger search area than the August observations, down to a limiting magnitude of 24.5. Gladman and Kavelaars reobserved the two satellites from August and identified two more new irregular satellite candidates: Siarnaq and Tarvos. Siarnaq, the brighter of the two, was detected at an apparent magnitude of 20. Shortly after the survey, the two candidates were reported to other astronomers for further confirmation.
  Between 25–29 September 2000, follow-up observations of the four irregular satellites were made at various observatories. Preliminary orbit calculations ruled out the possibility that the satellites could be foreground asteroids, confirming that Ymir, Paaliaq, Siarnaq, and Tarvos were indeed orbiting Saturn. The discovery of the four Saturnian satellites was formally reported by the International Astronomical Union on 25 October 2000, and was announced by Gladman's team a day later at a meeting hosted by the American Astronomical Society's Division for Planetary Sciences. The discovery of the four satellites raised Saturn's known moons to 22, surpassing Uranus's moon count of 21 at the time.
  Although Siarnaq was confirmed as a satellite, its orbit was poorly determined and required extensive follow-up observations. The moon was reobserved by the Kitt Peak National Observatory in December 2000, and later by the Palomar and La Palma observatories in early 2001. In the interim, Gladman's team had discovered eight more irregular satellites of Saturn, six of which were found in CFHT images from September 2000. By February 2001, the team surveyed 90 percent of Saturn's Hill sphere down to a limiting magnitude of 23 and discovered a total of 12 irregular satellites around Saturn, raising the planet's number of known moons to 30 and overtaking Jupiter as the planet with the most known moons until 2003.
caption: Discovery images of Siarnaq taken by the CFHT in September 2000