Siarnaq

Siarnaq is the second-largest irregular moon of Saturn. It was found on 23 September 2000 by a team led by Brett J. Gladman. The moon is named after the Inuit sea goddess Siarnaq, who is also called Sedna.

Siarnaq is the largest moon in Saturn's Inuit group of irregular moons. These moons orbit far from Saturn and move in the same direction as the planet turns. Scientists think these moons came from pieces of a bigger moon that broke apart long ago. This bigger moon was probably pulled into Saturn's orbit by gravity billions of years ago. Today, several smaller moons follow similar paths, suggesting Siarnaq may have been part of another collision after it formed.

Discovery

Siarnaq was discovered on 23 September 2000 by a team of astronomers. They were looking for faraway objects around Saturn using telescopes with special cameras. They found Siarnaq and another object called Tarvos. These discoveries added to the number of known moons around Saturn, giving it more moons than the planet Uranus at that time.

More observations showed these objects were really moons of Saturn. Later, more moons were found, so Saturn briefly had more moons than Jupiter before 2003.

Name

Siarnaq is the second-largest irregular moon of Saturn. It is named after the Inuit sea giantess or goddess. She rules the Inuit underworld called Adlivun. In some stories, she is also known as Nuliajuk and Sedna.

Siarnaq is said to live at the bottom of the ocean. People believe she created all sea life. In some tales, she was once a beautiful maiden who married a bird-man and was saved by her father.

The moon got its name in August 2003. This was one month after experts approved it. It was called Saturn XXIX, meaning it is the 29th moon of Saturn. Before its name, Siarnaq was known by a temporary name, S/2000 S 3. This name showed it was the third Saturn moon found in images from 2000. The discoverers picked Inuit names for these moons to honor different cultures.

Physical characteristics

Diameter and albedo

From infrared observations by the Wide-field Infrared Survey Explorer (WISE) spacecraft, Siarnaq is about 39.3 km (24.4 mi) wide.

Surface and composition

Siarnaq is light red in color. Its infrared spectrum looks like the Inuit-group satellites Paaliaq and Kiviuq, suggesting it might have come from the same larger body that broke apart.

The James Webb Space Telescope found a feature on Siarnaq linked to minerals that contain water. Unlike another moon named Phoebe, Siarnaq does not have much water ice. Instead, it has a type of carbon linked to organic materials. Siarnaq's makeup is very similar to another moon named Albiorix.

Siarnaq's brightness changes a little at some angles but gets much brighter at a special angle, suggesting its surface has loose material.

Shape and rotation

The Cassini spacecraft found that Siarnaq spins around once every 10.19 hours, the fastest of Saturn's irregular moons that move in the same direction as Saturn. It looks roughly triangular. Observations also showed the direction of its north pole, revealing a sideways tilt. This causes extreme seasons, much like the planet Uranus.

Orbit and group

Siarnaq travels around Saturn at an average distance of 17.9 million kilometers, taking about 896 days to complete its journey. Its path changes because of the pull of the Sun and other planets. Over many years, Siarnaq’s distance from Saturn can vary between 17.5 and 18.3 million kilometers.

Siarnaq is part of Saturn’s Inuit group of moons. These moons orbit in a forward direction but have unusual paths. The group is divided into three smaller groups based on their distance from Saturn. Siarnaq is in the outermost group and is one of seven known moons in this subgroup. These moons may have fewer small members because collisions might have removed many of them over time.