Siarnaq

Siarnaq is the second-largest irregular moon of Saturn. It was discovered on 23 September 2000 by a team of astronomers led by Brett J. Gladman. The moon was named after the Inuit goddess of the sea, Siarnaq, who is more commonly known as Sedna.

Siarnaq is the largest member of Saturn's Inuit group of prograde irregular moons. These moons orbit far from Saturn and move in the same direction as the planet rotates. Scientists believe the moons of the Inuit group came from pieces of a bigger moon that broke apart long ago. This larger moon was likely pulled into Saturn's orbit by gravity billions of years ago. Today, several smaller moons share similar paths around Saturn, showing that Siarnaq may have been involved in another collision after it formed.

Discovery

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

More observations helped confirm that these objects were truly moons of Saturn. Later, even more moons were found, so Saturn briefly had more moons than Jupiter before 2003.

Name

Siarnaq, the second-largest irregular moon of Saturn, is named after the Inuit sea giantess or goddess who rules the Inuit underworld called Adlivun. In other versions of Inuit legend, she is also known as Nuliajuk and Sedna. Siarnaq is said to live at the bottom of the ocean and is believed to have created all sea life. Sometimes, stories say she was once a beautiful maiden who married a bird-man and was later saved by her father.

The moon received its name in August 2003, one month after it was approved by a group of experts. It was given the Roman numeral designation Saturn XXIX, meaning it is the 29th moon of Saturn. Before its official name, Siarnaq was known by a temporary name, S/2000 S 3, indicating it was the third Saturn moon found in images from 2000. The discoverers chose Inuit names for this group of moons to honor different cultures.

Physical characteristics

Diameter and albedo

From infrared observations by the Wide-field Infrared Survey Explorer (WISE) spacecraft, Siarnaq is estimated to be 39.3 km (24.4 mi) in diameter.

Surface and composition

Siarnaq is light red in color, and its infrared spectrum is very similar to 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 studied Siarnaq and found a feature linked to certain 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.

Observations show that Siarnaq's brightness changes a little at some angles but gets much brighter at a specific angle, suggesting its surface is full of loose material.

Shape and rotation

The Cassini spacecraft found that Siarnaq spins around once every 10.19 hours, the fastest among Saturn's irregular moons that move in the same direction as Saturn. Its shape seems roughly triangular. Observations also helped determine the direction of its north pole, showing it has a sideways tilt, leading to extreme seasons, much like the planet Uranus.

Orbit and group

Siarnaq travels around Saturn at an average distance of 17.9 million kilometers, completing its journey in 896 days, or about 2.45 years. Its path changes due to the pull of the Sun and other planets. Over 200 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, which orbit in a forward direction but have unusual paths. This 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 seem to have fewer small members, suggesting that collisions may have removed many of them over time.