Kerbal Star Systems Wiki

The Kerbol System is the home system, expanded stock system, and Solar System analogue. It is home to 9 planets, 2 comets, many asteroids and 3 dwarf planets.


The Kerbol System is most well known for being the home of the Kerbals. However, the system's uniqueness spans more than what it seems. It is the largest system as far as number of bodies goes and one of the largest when mass is taken into account, suggesting Kerbol formed in an environment rich in heavy compounds. It is also one of the few star systems known to have a single G-type star.

Formation and evolution

Four and a half billion years ago, a small portion of an interstellar dust cloud several light-years across began to collapse in on itself, forming into a hot disk of hydrogen, helium, and an assortment of heavier elements. Over time, the center of this disk became hot enough to become a protostar, surrounded by 12 recently formed proto-planets. Three of those proto-planets never reached planethood, and remained as dwarfs (Dres, Kel, Naith). The rest eventually grew big enough to classify as planetary mass objects, with the inner solar system composed of four slowly growing rocky worlds (Moho, Eve, Kerbin, Duna), while the outer system was populated by four rapidly growing gaseous worlds: Jool, Voon, Naal, and Oran (in that order). At the time, it was estimated that the outer Kerbol system was much denser than present day, with gas giant orbits twice as close to each other than they are now. Over the next few million years, the Kerbol System underwent drastic changes. Kerbol became a fully-fledged star, and began steadily growing brighter. Jool and Voon entered a historic 1:2 resonance, which began causing gravitational chaos in both the inner and outer solar system. It is thought that Jool entered the inner solar system for brief period of time, robbing the inner solar system of disk material and stunting Duna's growth, resulting in it being merely one-tenth of Kerbin's mass (when it otherwise would have been close to Kerbin's mass, if Jool had not intervened). It is also thought that the Jool-Voon resonance catapulted Naal and Oran into higher and higher orbits, where they eventually traded places (making Naal the furthest planet from the sun instead of Oran). It is also believed that during this early period of the Kerbol System that stars were clustered a lot closer than they are today, and so a close gravitational interaction with another solar system (likely Kirb, Kelin, or Kernim before they came together as Nova Kirbani) allowed Kerbol to capture an extra gas giant in an extremely wide orbit: Hypat. Jool and Voon eventually escaped the 1:2 resonance as Jool returned to the outer system, and the planets slipped into roughly the positions that they are in today. Over the next billion years, Eve, Kerbin, and Duna, all supported liquid water on their surfaces and may all have supported life. Eventually, Eve entered a runaway greenhouse state and Duna lost most of its atmosphere, becoming a cold and dry desert planet. Kerbin developed photosynthetic life and gained a primarily Nitrogen-Oxygen atmosphere. Approximately one billion years ago, the first multicelluar life appeared on Kerbin. Approximately 5 million years ago, Laythe thawed to become a wet world (that is if you chose Tropical Laythe instead of the default Icy Laythe), and the first Kerbal ancestors appeared. Being more intelligent than any other living thing in the Kerbol System, these creatures began to spread and make tools, while often finding the time to look up and wonder about their place in the universe.


Kerbol is regarded as being the first astronomical discovery by Kerbalkind. It is known as being the main light source of Kerbin and the driving force of life. It is highly advised for Kerbals not to look directly into Kerbol, especially considering the effect shiny objects have on the average Kerbal.


Inner Kerbol System

Inner planets


The closest planet to Kerbol and the smallest planet in the Kerbol System (0.055 Kerbin masses). Moho has no natural satellites; besides impact craters, its only known geological feature is a canyon produced by a period of contraction early in its history. Moho's very tenuous atmosphere consists of atoms blasted off its surface by the solar wind. Although it is the closest planet to Kerbol, it is not the hottest.


Eve is the hottest planet in the Kerbol System. Due to its super dense atmosphere and high quantity of greenhouse gases, it has trapped all heat captured by Kerbol. It also holds unique features such as "only planet to rotate backwards" and "only planet who's day is longer than its year". Due to it rotating in the opposite direction, Eve has developed no natural satellites, any of which have fallen into the planet. Scientists believe the planet may have once been a more Kerbin-like world.


Kerbin is what we call home for now. It is the 3rd planet from Kerbol and the only one we know so far to be inhabited by lifeforms. It has one moon, which Kerbals refer to as Mun, and sits right in the habitable zone, a region around a star where liquid water can be supported.


Duna is the current record holder for the most Kerbin-like world in the Kerbol System. Although it is smaller, colder, and drier, it has extensive evidence of once being a Kerbin-like planet, with even possible evidence of life once existing there.

Asteroid Belt

The Asteroid Belt is regarded as the boundary between the inner Kerbol System and the outer Kerbol System. It is guarded by a plethera of asteroids, including Vern and Dres.


Vern is the largest asteroid in the Asteroid Belt. It is also the largest non-spherical body orbiting Kerbol. It makes up less than 1/8 of the total mass in the asteroid belt.


Dres is the largest body in the Asteroid Belt, a region of small asteroids between Duna and Jool. Dres composed of about a third of the mass in that region and is the only body there large enough to sustain hydrostatic equilibrum.

Outer Kerbol System

Outer planets


Jool is known to Kerbals as being the "bright green dot". It is the second largest planet in the Kerbol System, but it has some of the largest moons.


Voon is regarded by astronomers as being the largest and prettiest planet in the Kerbol System. It is the only planet in the system with well defined rings, and also boasts the most moons, one of which being the only moon with a dense atmosphere and the only body in the system with seas of methane.


Oran is the first ice giant in the Kerbol System. It was also the first planet to be discovered due to its distance from Kerbol. It is regarded by astronomers as being the catalyst for rapid discovery of planets shortly after.


Naal is the first planet to be discovered mathematically. It is also known as being the bluest of the bodies in the Kerbol System. It is believed that the outward migration of Naal messed up the orbits of bodies in the Trans-Naalian region.



Kirnel is the short-period comet in the Kerbol System. Its orbit brings it to being the closest body to Kerbol, while the apoapsis brings it beyond the orbit of Jool.


Chur is a small comet that was captured into a smaller orbit by the influence of Jool and Voon. It is also the smallest comet discovered so far.


Minmus is the long-period comet in the Kerbol System. Its orbit gets as close as just within Kerbin to beyond the orbit of Naal. It is the larger and icier of the 2 comets in the Kerbol System.

Trans-Naalian region


Kel is the most widely-known Trans-Naalian Object (TNO) in the Kerbol System. Although it is too small to be considered a planet, it is one of the more active bodies in the system.


Hal is a TNO that rotates very rapidly. It is also well known for its large tholin deposits on the surface.


Naith is the largest TNO discovered radius-wise. It is also well known for its lack of tholins on the surface.


Hypat is the farthest planet in the Kerbol System, and the most irregular one too. It is well known for being the first planet to be discovered using an orbital telescope.

Habitable Worlds

The Kerbol System hosts one habitable world and four organic worlds. Two planets (Kerbin, Duna) reside in the habitable zone.

Visual Diagram

Kerbol System UPDATED.png

List of Bodies

In the Kerbol System, there are 9 planets, 4 dwarf planets, 3 comets, many asteroids, and many moons.