Moons of outer solar system - S/2007 (148780) 1 (moon of Altjira)

S/2007(148780)1, is a retrograde natural satellite of 148780 Altjira, which is a binary classical Kuiper belt object (cubewano).

S/2007(148780)1, is large compared to the primary, estimated diameter 246 km vs 340 km.

S/2007(148780)1 is the 25th largest moon in the Solar System currently known.

Discovery

S/2007(148780)1 was reported in March 2007.

Naming

Upon discovery, the moon was issued a provisional designation, S/2007 (148780)1.

Stats

Diameter (estimated): 246 km (200 - 360 km)

Semi-major axis: 9904 ± 56 km

Orbital Period: 139.56 days

Rotation Period: ?

How big is it?

Altjira and S/2007(148780)1 are so far away in the outer solar system that we don't know for sure how large they are. 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.