Weywot

Weywot, officially (50000) Quaoar I Weywot, is the only known moon of the trans-Neptunian object and possible dwarf planet 50000 Quaoar. Discovered by Michael Brown and T.A. Suer using images acquired by the Hubble Space Telescope on 14 February 2006, its existence was announced in an IAU Circular notice published on 22 February 2007. Weywot has an estimated diameter of 170 km (110 mi) (approximately 15% of its primary). The satellite was found at 0.35 arcseconds from Quaoar with an apparent magnitude difference of 5.6.

Orbit
Two possible orbits for Weywot have been determined from the observations: the first is a prograde orbit with an orbital inclination of 14 degrees, the second a retrograde orbit with an orbital inclination of 30 degrees (150 degrees); the other parameters are very similar between the two orbits. Weywot orbits at a distance of 14,500 km (9,000 mi) from Quaoar and has an orbital eccentricity of about 0.14, it completes one orbit in about 12.5 days.

Physical characteristics
As of 2019 Weywot is estimated to be around 170 km (110 mi) in diameter, based on a stellar occultation by Weywot in 2019. Weywot was estimated to be 81 km (50 mi) in diameter, based on observations with the Herschel Space Observatory in 2013. Prior to the Herschel Space Observatory measurements, Weywot was measured be about 74 km (​1⁄12 of Quaoar) according to its apparent magnitude, under the assumption that Weywot has an equal albedo and density to Quaoar. Weywot is estimated to only have ​1⁄2000 the mass of Quaoar.

Name
Upon discovery, Weywot was issued a provisional designation, S/2006 (50000) 1. Brown left the choice of a name up to the Tongva, whose creator-god Quaoar had been named after. The Tongva chose the sky god Weywot, son of Quaoar. The naming of Weywot was officially announced in a Minor Planet Circular notice published on 4 October 2009. It was thought that Weywot may have originated from a collision with Quaoar and another large Kuiper belt object.

Extra
WEYWOT is on of Two Hubble WFPC2 observations of Quaoar and Weywot taken on March 20 and 28, 2008 show the pair of Kuiper Belt Objects moving against the background of stars. These are two of the observations that were used to determine the mass of Quaoar from the size of Weywot's orbit.