Thresomin
Thresomin as seen through a telescope on the surface of Mesbin
Name: Thresomin
Designation: Kaywell A d V
Discovery (Mesbin): Direct telescopic imaging (though it is visible to the unaided eye)
Thresomin was discovered by astronomers watching Statmun. Once exactly every three Mesbin Days, a star-like object would go behind Statmun. This turned out to be an object orbiting in a 3:1 resonance with Mesbin's rotation and Statmun's orbit. Thresomin is a polarizing object for many astronomers and astronomy educators. When it was discovered, it was hailed as the fifth moon of Mesbin. However, around the same time, astronomers were discovering many, many small moonlets in orbits quite similar to Thresomin. Those moonlets, now understood to be a diffuse ring system left over from the destruction of Statmun's compositional parent body, show similar spectral characteristics to Thresomin--rich in silicates and metals as well as hints of volatile ices. While it is certainly the largest of these objects to date, it is not yet agreed upon by astronomers whether this is simply the largest moonlet or the smallest moon--a problem paralleled in discussions of certain dwarf planets orbiting Kaywell. Its name means "Small Object in Three-To-One Resonance."
- Dimensions = 4.6 km x 5.8 km x 5.8 km
- Polar Radius = 2310 m
- Mass = 5.981 x 10^15 kg
- Density = 7.2497 x 10 g/cm^3
- Polar Surface Gravity = 0.005576 Gee
- Rotation Period = 5103 seconds (1 hour 25 minutes 3 seconds)
- Parent Body = Mesbin
- Semi Major Axis = 5,498,502.912 meters
- Orbital Period = 5103 seconds (1 hour 25 minutes 3 seconds)
- Eccentricity = 0.0062
- Inclination = 0.23°
- Mean Anomaly At Epoch = 334°
- Argument of Periapsis = 230°
- Longitude of Ascending Node = 10°
Thresomin is likely the second largest surviving chunk of the Manonam/Pluto-sized satellite that was broken up to form Statmun. It is mostly iron by volume as deduced by its density, but its surface is covered largely in rock with traces of subsurface volatiles.
Its primary role in space program development around Mesbin is that of a fuel stop. From a delta-v perspective, Thresomin is about halfway between low Mesbin orbit and low Kerbmun orbit (or low Troymin orbit). It is also an early career game destination for space probes, though its low sphere of influence size means that patched conics display and maneuver nodes are likely necessary to reliably intercept this satellite.