I'm trying to build a table with the Min and Max Radius and Mass of Solar bodies. In order to get data to be able to random generate other solar systems. This is a basic exercise, I'm pulling data from the maximum and minimum classification we have in the Solar System Example:

Body Type Min. Radius (km) Max. Radius (km) Min. Mass (kg) Max. Mass (kg)
Planet 470 71492 1.471*10e22 1.899*10e27
Dwarf Planet 400 1188 2.000*10e20 1.471*10e22
Sat. 400 2634 2.000*10e20 1.340*10e23

When I was researching the Asteroids I got into conflicting data. It appears they can range from 1 meter into the 400 km but if I start reading about TNOs this number goes way in into the Dwarf Planet sizes. So I think I'm struggling to define the range for Asteroids since it appears they make a distinction based on their location on the Solar System, or am I reading this wrong? Should for generation of solar system purposes consider the range of 1m to 400km if the body resides in the inner system, and classify everything else has dwarf planet if it lives in the outer system?

Appreciate any help and resources for further reading.


1 Answer 1


In truth, there are only "solar system bodies" which range in size from millimeters to the size of Jupiter. The division into "asteroids", "dwarf planets" and "planets" is a human choice for practical purposes, rather than a "natural" description.

So to summarise how "we" choose to classify solar system bodies:

  1. Planets are major bodies, those that are both in hydrostatic equilibrium (ie rounded) and which dominate their orbits (ie have "cleared their orbit").
  2. Dwarf planets are secondary bodies, they are rounded, but do not dominate their orbit.
  3. Small solar system bodies (SSSBs) are minor bodies in orbit around the sun. They are not rounded.
  4. Moons are natural satellites, they orbit one of 1,2, or 3, and are large enough to be observed as an individual body.
  5. SSSBs and dwarf planets can be further classified by where they are found. Those close to the sun are called "asteroids". More distant object are called "centaurs", or "TNOs", "plutoids" and so on
  6. Comets are objects that give off vapour or dust when warmed by the sun.

So for the sake of classification, there are three factors we consider, The gravitational size of the body, whether the body is in hydrostatic equilibrium and where the body is compared to other solar system bodies.

Most asteroids have a mass that makes them sssb, but at least 1 asteroid is also a dwarf planet. Most TNOs are SSSBs, but (as a result of observation bais.

  • $\begingroup$ This makes complete sense. Just two question is it Hydrodynamic or hydrostatic equilibrium? and In theory the cap would be when an object approaches the threshold to be come a brown dwarf otherwise I can just go beserk on the generation within 1 cm to the size of Jupiter? $\endgroup$ Commented Apr 8 at 22:07
  • $\begingroup$ hydrostatic, I've fixed the answer. Whether something is in hydrostatic equilibrium and gravitationally rounded depends on both its size and its composition. Ice balls are quicker to flow at small sizes than rocky (or metallic) ones. The number of items follows an exponential distribution, but there are already questions here about that. $\endgroup$
    – James K
    Commented Apr 8 at 22:20

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