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Kerbol (officially called the Sun, and also known as the Star) is the central star of the Kerbol System. Five planets are known to orbit it: Moho, Eve, Kerbin, Duna and Jool and two dwarf planets Eeloo and Dres.

Compared to our own Sun, Kerbol has a 113 times lesser mass and 3 time smaller radius. Kerbol's other attributes can be used to make the following comparisons: It has the temperature of a K Class main sequence star, the radius of a M class star, the luminosity of a G class star, and the mass of a sub-brown dwarf. In reality, such a star cannot exist as the minimum mass of a star is approximately 75 times the mass of Jupiter, a full power of ten higher than that of Kerbol.

Orbiting Kerbol

Orbits just above the surface have an orbital period of 409.214 minutes and a speed of 66.945 km/s.

While Kerbol can be reached from Kerbin's orbit by using a Hohmann transfer orbit, doing so requires a Δv of about 8 km/s. The most efficient way to reach Kerbol from Kerbin orbit is to use a bi-elliptic transfer. With a sufficiently-distant apoapsis, the required ΔV to sundive can be reduced to under 4 km/s at the expense of drastically-increased flight time.

The sphere of influence of Kerbol is infinite. A orbit around Kerbol is inescapable, and achieving gravitation-free flight is impossible. Once the apoapsis reaches a certain point, the game will say that it 68 years to reach. This oddity occurs because times in Kerbal Space Program are limited to 232-1 seconds as a consequence of how numbers are handled.

Physical appearance

The equatorial radius of Kerbol is almost four times that that of Jupiter and 43.6 times larger than Jool's radius, currently the largest known planet. Kerbol's heat will always destroy a craft, even with the "No crash damage" cheat enabled, and makes landing on Kerbol impossible.

Squad has long-term plans for solar flares and prominences that would make a low Kerbol orbit even more dangerous.[citation needed] It is currently possible for a craft to approach to roughly 1300 meters altitude before it explodes due to overheating. No known way of landing on Kerbol exists. One can attempt to place edited parts on the surface, but they bounce erratically at a few hundred to a few thousand m/s if they do not explode.

Until version 0.11 Kerbol was a point of light in the skybox impossible to reach, although no “surface” existed. Up to version 0.13.3 dropping below the “surface” was still safe, but a ship can break up from the extreme gravity gradients and/or be shot outwards at large fractions of the speed of light.

If close enough it is possible to see that the dark spots are indented.

Reference Frames

Time warp Minimum Altitude
5× 3 270 000 m
10× 3 270 000 m
50× 6 540 000 m
100× 13 080 000 m
1 000× 26 160 000 m
10 000× 52 320 000 m
100 000× 65 400 000 m

All Kerbol orbits are in an inertial reference frame. In the old demo, getting close enough to experience the lower maximum time warps results Deep Space Kraken attacks.


  • The name “Kerbol” was created by forum members and never appears in the game. Officially, the star is simply referred to as “the Sun," though the lead developer mentioned that its name could change once the need to differentiate it from other stars arises.
  • Kerbol has just under twice the surface gravity of Kerbin, but only slightly more than Eve.



  • Art pass.
  • Actual model added, new sprite/flare effect, size changed.
  • Added solid surface (featureless invisible plateau ~4500-4700 km above nominal radius).
  • Added Gravity, nominal radius of 65,400 km.
  • Made it possible to reach Kerbol.
  • Initial Release.