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Kerbol as seen from orbit.
Physical Characteristics
Equatorial radius 261 600 000 m
Equatorial circumference 1 643 681 276 m
Surface area 8.5997404×1017 m2
Mass 1.7565459×1028 kg
Standard gravitational parameter 1.1723328×1018 m3/s2
Density 234.23818 kg/m3
Surface gravity 17.1 m/s2 (1.747 g)
Escape velocity 94 672.01 m/s
Sidereal rotation period 432 000.00 s
20 d 0 h 0 m 0 s
Sidereal rotational velocity 3 804.8 m/s
Synchronous orbit 1 508 045.29 km
Sphere of influence
Atmospheric Characteristics
Atmosphere present ✓ Yes
Atmospheric pressure 16.0000 kPa
0.157908 atm
Atmospheric height 600 000 m
1.6×10-7 atm
Temperaturemin 3741.80 °C 4014.95 K
Temperaturemax 9348.05 °C 9621.2 K
Oxygen present × No
Scientific multiplier
Surface N/A
Splashed N/A
Lower atmosphere 1
Upper atmosphere 1
Near space 11
Outer space 2
Recovery 4

Kerbol (officially called the Sun and sometimes the Star) is the parent star of the planetary system in KSP, popularly referred to as the Kerbol System. As of version 0.90.0, it has seven known children: the planets Moho, Eve, Kerbin, Duna and Jool and the two dwarf planets Dres and Eeloo.

Kerbol has the pale yellow-orange color of a Class K main-sequence star. Its absolute bolometric magnitude is approximately +10.

In-game Description

The Sun is the most well known object in the daytime sky. Scientists have noted a particular burning sensation and potential loss of vision if it is stared at for long periods of time. This is especially important to keep in mind considering the effect shiny objects have on the average Kerbal.

Kerbal Astronomical Society

Orbiting Kerbol

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-elliptical 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.

Orbits just above the surface have an orbital period of 409.214 minutes and a speed of 66.945 km/s. At around 1,340m above the surface, there is a sudden increase in temperature which causes destruction to vessel parts and kerbonauts on EVA; this marks the closest sustained altitude possible, though catastrophic dives to lower depths are possible.

The sphere of influence of Kerbol is infinite. An 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 takes 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.

With a powerful enough ship, it is possible to get to the point where one is "escaping" Kerbol. This can easily be achieved (as of 0.23.5). While the actual escape never occurs, the info tab will display the craft's situation as "escaping". It will reach a point where the course plotted by the game ends, and the spacecraft begins plotting its own course. Presumably, this will continue indefinitely, as the time required to find out what would happen would take several years.

Physical appearance

The equatorial radius of Kerbol is almost four times than that of Jupiter and 43.6 times larger than Jool's, the largest planet currently known. 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. Asteroids have a maximum temperature tolerance of 1038 so do not overheat even under these circumstances, but are instead destroyed at an altitude of -250m, which shows in the end flight dialog as "crashed into the surface of the sun" or similar.

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, one can see that the dark spots are indented.


The “corona” surrounding Kerbol is not the actual size of the sun as it appears. It will shrink and grow relative to the location of the viewpoint, just as the size of Kerbol does normally. However, it won't shrink past a certain point, and if the sun is viewed from a far enough point, the corona is still very visible. This is apparent when using camera or telescope mods that remove the corona and show Kerbol's true size, which is usually much smaller than the corona appears.

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 in 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.
  • It is possible "Kerbol" is a portmanteau of "kerbal" and "sol", the Latin name of the Sun.
  • Kerbol has just under twice the surface gravity of Kerbin, thus only slightly more than Eve's.

Real-world comparison

While otherwise analogous to our own real-life Sun, Kerbol has 1/113th the mass and a 1/3rd its radius. Kerbol's other attributes can be used to derive the following statistics: it has a luminosity of approximately 4.5 Yotta-watts (0.012 Solar luminosities) based on the temperatures of planets Eve, Kerbin, and Duna; a surface temperature of approximately 3100 K based on its size and luminosity—the temperature of a Class M main-sequence star; the radius of a red dwarf; 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 greater than that of Kerbol. However, many astrophysical properties in KSP are effectively scaled down for gameplay.



  • 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.