2002 MS4 is a large trans-Neptunian object. 2002 MS4 is possibly the 15th largest TNO and 6th largest Cubewano currently known.
Discovery
2002 MS4 is discovered on June 18, 2002 by Michael E. Brown and Chadwick A. Trujillo at Palomar Observatory.
2002 MS4 has precovery images back to 1954.
Stats
Estimated Diameter: 726 km (603 - 849 km)
Aphelion: 47.86 AU
Perihelion: 35.51 AU
Semi-major axis: 41.67 AU
Orbital Period: 268.98 years
Rotation period: 16.34 hours
Date discovered: 2002.6.18
Satellite: ?
Classification: TNO, KBO - Cubewano
Orbit
2002 MS4 currently 47.2 AU from the Sun and will come to perihelion around 2122.
How big is it?
2002 MS4 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
Mike Brown's automatically updated website lists it as a highly likely dwarf planet.
The Spitzer Space Telescope has estimated it to have a diameter of 726 ± 123 km.
A recent estimate by the Herschel team of the diameter is 934 km. That would lift it into the top 10 largest TNOs. Apparently the body has a lower albedo than originally assumed.
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