Kharun

What is Kharun like?

Kharun is a moon of Kharsis, the system’s arid mining planet. It is a lunar-type moon: dry rock, like Earth’s Moon.

• Size. 780 km in radius.
• Gravity. 0.698 m/s².
• Air. Tenuous: almost vacuum, a very thin layer of gas (an exosphere) that is 97% argon. Impacts from space rocks and argon formed in its own rock top it up.
• Haze. Only dust charged with static electricity and whatever the impacts throw up.
• Going outside. Outside work means a full EVA, in a spacesuit.

Where is it?

Kharun orbits 75,595 km from Kharsis, with its axis tilted eleven degrees. It is tidally locked: it spins at exactly the rate at which it goes round the planet, once every 2.75 hours. That is why it always shows Kharsis the same face.

From Kharun, Kharsis never moves in the sky. It is a disc nine and six-tenths degrees across, always above the same point on the horizon. It wobbles only six degrees, so slowly that it takes a whole shift to notice.

Why are its two faces so different?

The face turned towards Kharsis never has full night. A permanent ochre light bathes it, which the miners call “the eye”. That face is watched and inventoried, and it runs on logistics.

The far face is the opposite. It is the only place in the inner system over which Kharsis has no line of sight. The inner system is the part closest to the star.

For much of each turn, the far face has nothing in its sky but stars. Then Erran, la Errante (‘the wanderer’), another moon of Kharsis, rises over the horizon. It hangs wide and pale for a while and leaves.

What is there to fear?

On the far face there is no coverage and no constant light. And the windows of visibility can be worked out in advance. That makes Kharun the system’s stealth body. Smuggling and interception there run to the clock.

The dossier on the moons of Aurin shows how the two sides, the Zenith and the Nadir, handle it:

“The Zenith have a complete inventory of the visible face. On the other, their reports have said ‘no operational interest’ for nine years, which is exactly how long the Nadir have gone without needing them to say anything else.”

Dossier on the moons of Aurin

In other words, it suits the Nadir that those reports stay as they are.

What is odd about its orbit?

Kharun is the middle link of the Kharsis chain:

Body	What it is	Orbit time
Kravane	Moon	1.375 hours
Kharun	Moon	2.75 hours
Ashkar	Captured asteroid	5.5 hours

Each takes exactly twice as long as the one before: a 1:2:4 ratio, exact down to the last digit. Because of their phase, the three never line up at once. They always rise and set at the same point on the horizon. The miners of Kharsis have used them as a clock for forty years without ever correcting it.

None of these orbits is worked out from the masses. They are looked up in the Tabla de Fases, the system’s table of measured orbits.

The Registro Aura, the first catalogue of the system, gave it the suffix -un. It kept it for captured bodies or those with unresolved orbits.