Ku

Ku is a large orange-colored super-Jupiter orbiting Rexau.

Properties
Ku is a huge gas giant in orbit of Rexau. It has a mass of 450 M🜨, a radius of 11🜨. It has an axial tilt of 7 degrees, and one day on Ku would take 29 hours.

Orbit
Ku orbits Rexau at an average distance of 0.03 AU, with an orbital eccentricity of 0.003. Its orbit is the plane of reference for the Rexau system, and ergo has an inclination of 0 and orbits prograde. Ku's orbit brings it close enough to Rimelu to destabilize the latter's orbit.

Atmosphere
The atmosphere of Ku is composed of primarily hydrogen, some helium and ammonia, and traces of methane, water vapor, ethane, and hydrogen deuteride.

Magnetosphere
Ku's immense magnetosphere protects it and its nearest moons from most forms of solar weather. Its magnetosphere extends several dozen times its own radius past its core.

Moons and rings
Ku has 1 major moon, Lawa, which is also the homeplanet of the Njetra. There are several dozen minor moons in various orbits. There are thin and tenuous rings around Ku, shepherded either by orbital resonances with Lawa or by the countless minor moons.

Significance
Without Ku's magnetosphere, Lawa would've been sterilized by the solar weather of Rexau, and life would never have stayed long enough on Lawa to create sentient species in the form of the Njetra.

The Njetra saw Ku every day from their vantage point of Lawa, and it became a major part of their religions and culture. There are several Njetra stations in orbit of Ku, and several facilities scattered around its moons.

Deuterium collection
The Njetra have designed skimmer ships capable of filtering hydrogen deuteride from the atmosphere of Ku, separating it into hydrogen and deuterium, and using the deuterium for fusion reactors or fusion powered spacecraft thrusters.