Sennim as seen from orbit.
Moon of Cyran
Orbital Characteristics
Semi-major axis 120 974 986 m [Note 1]
Apoapsis 145 169 983 m [Note 1]
Periapsis 96 779 989 m [Note 1]
Orbital eccentricity 0.2
Orbital inclination 3 °
Argument of periapsis 4 °
Longitude of the ascending node 71 °
Mean anomaly 2 rad (at 0s UT)
Sidereal orbital period 255 946 s
11 d 5 h 5 m 46.1 s
Synodic orbital period 257510.1 s
Orbital Velocity 2 425 to 3 637 m/s
Longest Time Eclipsed 6603 s
Physical Characteristics
Equatorial radius 500 000 m
Equatorial Circumference 3 141 593 m
Surface area 3.1415927×1012 m2
Mass 2.7550567×1022 kg
Standard gravitational parameter 1.8387469×1012 m3/s2
Density 52 617.707 kg/m3
Surface gravity 7.35 m/s2 (0.75 g)
Escape velocity 2 712.01 m/s
Sidereal rotation period 3 600.0000 s
1 h 0 m 0 s
Sidereal rotational velocity 872.66 m/s
Synchronous orbit 345.13 km
Sphere of influence 9 489 526.2 m [Note 1]
Atmospheric Characteristics
Atmosphere present ✓ Yes
Atmospheric Pressure 121.590 kPa
1.2 atm
Scale height  m
Atmospheric height 80 000 m
1.2×10-6 atm
Temperaturemin -32.67 °C 240.48 K
Temperaturemax -3.15 °C 270 K
Oxygen present × No
Scientific multiplier
Surface 9
Splashed 9
Lower atmosphere 8.5
Upper atmosphere 8
Near space 7.5
Outer space 7
Recovery 5

  1. 1.0 1.1 1.2 1.3 The distances are given from the bodies center not surface (unlike ingame)
Sennin is the fifth moon of Cyran from the Planet Cyran mod, and the largest of the six moons in orbit around the giant planet.
PlanetCyran Sennim

In-Game description

A world with a dense atmosphere and lakes of mercury, this world bears a striking resemblance to Kerbin, yet at the same time is nothing like it. A bit like Eve, only less hard to land and return from. And this planet looks strangely green... perhaps it's vegetation? Only one way to find out...

Kerbin Astronomical Society


Physical properties

Sennim has a radius equal to that of Laythe, although its surface gravity is slightly lower, indicating that the moon is less dense. It's radius is 1 Laythe radus or 0.833 Kerbin radii while its surface gravity is 0.75g. Unlike Laythe, however, Sennim is not tidally locked and has lakes instead of oceans, the surface is mainly land. Said lakes are not water, instead being comprised of liquid mercury that is over thirteen times the density of water. It partially resembles real-life Titan in some aspects.

The dry sections of the moon are covered in gentle hills and mountains, with the teal of the lowlands giving way to lime green and cyan as altitude increases.


Sennim has a dense atmosphere that is rich in Chlorine and Hydrogen. Although Sennim is smaller than Kerbin and has a lower gravity, it has an atmospheric pressure of 1.2 times that of Kerbin, therefore parachutes and wings are very effective when trying to land.

The following table gives atmospheric pressure in Sennim's atmosphere at varying heights above the datum sea level:

Altitude (m) Pressure (Pa) Pressure (atm)
0 121 582 1.200
2 500 78 155 0.771
5 000 46 915 0.463
7 500 32 360 0.319
10 000 21 889 0.216
12 500 15 013 0.148
15 000 10 252 0.101
20 000 5 315 0.052
25 000 2 613 0.026
30 000 1 094 0.011
35 000 405.1 0.004
40 000 196.3 0.002
50 000 76.66 0.001
60 000 18.55 0.000
70 000 1.649 0.000
80 000 0 0.000


Sennim has seven biomes in total, and these are:

Sennim Biome Map

Sennim biome map

  • Green Poles
  • Lakes of Mercury
  • Slopes of Deuterium
  • Hills of Kirbian
  • Highlands of Insomnia
  • Mountains of Qusad
  • Peaks of Tritium


Quote from the author of the Planet Cyran mod:

With Sennim I wanted to to something very different: create a world with extra-terrestrial life. I quickly got the idea of giving it silver oceans of Mercury, a metal that is liquid at room temperatures. After some in-game experimenting with VertexPlanet I actually managed to pull it off. I also made various textures for both the surfaces of the planets, the oceans, and even the terrain scatter in Sennim's case. I actually planned on giving Sennim a sandy golden atmosphere, but whilst editing the atmosphere in-game with KittopiaTech I accidentally gave it a green color instead of golden. I actually liked the green color, so I saved that color in the config file, then made a screenshot and isolated the color using an image editing program so I could use it for the ambient color and rim color. It's funny how I then forgot about this change and accidentally gave Sennim a golden atmosphere in every image despite having given it a green atmosphere.

The White Guardian


  • Sennim is the only Kopernicus planet thus far that features custom trees, or trees in general.
  • Sennim is one of the few Kopernicus planets to feature custom ocean and surface textures.