The Sun (unofficially called Sun or the Star, along with Kun, Kol, Zun and most famously of all Kerbol) is the parent star of the planetary system in KSP, cannonly to as the Sun System.(not to be confused with the real life Solar system, and it's star Sun/Sol)

“Kerbol” is a fan-made portmanteau of “Kerbal” and “Sol” — the Latin name for the real-life Sol. In the past it was an unnamed directional light source at infinite distance, so the fans on the KSP forums invented and popularized the name.

Kun, Zun, and Kol are alienized versions of our own Star, which were also used early on, and Sun and The Star are currentry used for convenience, however at the moment the only canon name is The Sun.

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 The Sun

Escaping the SOI of any other body will place an object in orbit around The Sun. This will give a Science situation of being in space high over The Sun until an altitude less than 1,000 Mm is reached. Low orbit can be reached by using a standard Hohmann transfer; from Kerbin's orbit this requires about 8 km/s of change-in-velocity (Δv). The more efficient way to reach low Sun orbit, at the expense of drastically increased flight time, is to use a bi-elliptical transfer. With a sufficiently-distant apoapsis, the required Δv to “sundive” from Kerbin orbit can be reduced to under 4 km/s.

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

The sphere of influence (SOI) of The Sunis infinite, making The Sun inescapable. Thus, achieving gravitation-free flight is impossible. Once the apoapsis reaches a certain point, the game will report 68 years to reach it. This oddity occurs because times in KSP 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 the info tab will display the craft's situation as “escaping” The Sun. The end of the patched conics path plotted by the game can be reached, at which point the spacecraft begins drawing a course behind it. But the actual escape never occurs. Presumably, this state would continue indefinitely, as the time required to find out what would happen would take several years even at maximum time acceleration.


No known way of landing on The Sun exists, even with all cheats enabled. The overheating effect quickly destroys parts before they can reach the surface. Interestingly, asteroids have a maximum temperature tolerance of 1038 so do not overheat even under these circumstances, but are instead destroyed at an altitude of -250 m, which shows in the end flight dialog as "crashed into the surface of the sun" or similar, rather than ever landing.

One can attempt to place edited parts on the surface, but they bounce erratically at a few hundred to a few thousand meters-per-second if they do not explode.

Temperature and Luminosity

The Sun's visible surface, its photosphere, has a temperature of 5840 K. This temperature, along with the the star's yellow color, suggests that Kerbol is a Class G main-sequence star. Above the photosphere is a thin and hot atmosphere that is analogous to a chromosphere. The chromosphere extends to a height of 600 km and has at its base a pressure of 16 kPa. The temperature of the chromosphere decreses with increasing altitude until reaching a minimum of 4000 K at a height of 50 km. Above 50 km the temperature increases with increasing altitude. The maximum temperature of 10,000 K is reached at the atmosphere's extreme upper limit.

Based on its given size and temperature, The Sun's luminosity would be 56.7 yottawatts, however this is contradicted by other in-game physical parameters. The value of the solar constant at Kerbin is 1360 W/m2, which implies a solar luminosity of 3.16 yottawatts (0.008 Solar luminosities) and a surface temperature of 2840 K. These values are consistent with a Class M red dwarf.

Physical appearance

The equatorial radius of The Sun is almost four times than that of Jupiter and 43.6 times larger than Jool's, the largest planet currently known. The Sun has the yellow color of a Class G main-sequence star and its absolute bolometric magnitude is approximately +10. If close enough, one can see that the dark spots are indented.

The “corona” surrounding The Sun 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 The Sun 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 The Star's true size, which is usually much smaller than the corona appears Reference Frames

Warp Minimum Altitude
5× 3 270 000 m
10× 3 270 000 m
50× 6 540 000 m
100× 1 380 000 m
1 000× 26 160 000 m
10 000× 52 320 000 m
100 000× 65 400 000 m


  • 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.
  • The Sun 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 Sol/Sun, The Sun has 1/113th the mass and a 1/3rd its radius. The Sun's other attributes can be used to derive the following statistics: it has a luminosity of approximately 3 yottawatts based on the solar constant at Kerbin; a defined surface temperature of 5840 K (that of a Class G star), but a temperature less than 3000 K based on its size and luminosity (that of a Class M 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 The Sun. However, many astrophysical properties in KSP are effectively scaled down for gameplay.

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