Is there any function that can describe the distribution* of asteroid diameters expected within an*' asteroid belt?

*: distribution as frequency of occurrence within the asteroid belt or absolute numbers, not as positional distribution or orbits inside the belt.

*':Not THE asteroid belt. So the answer could/should fit Sol's 'main' asteroid belt, but also any rather usual one on any other star system.

Possible independent variables used by the model given

The fewer used the better, as the model will be broader, but if by introducing any the precision of the result increases by a magnitude, then you are welcome. The variables at my disposal to find out the distribution of sizes are:

  • Initial mass of the belt on system formation.
  • Inner and outer radius of the ring.
  • Current age of the system.
  • Star(s) radius, mass, luminosity and temperature.
  • Planets around, and their masses and orbital characteristics. (this would not include planetesimals produced by the model, of course)

You can add any constant that you find necessary.


The more general the solution presented, the better, but any amount of them taken are acceptable to answer the question.

  • Considering a star system old enough to be stable.
  • Constant density of the bodies in it.
  • It's a rather standard main belt. This means that it does not need to represent oort cloud or anything further than ~100AU, neither heavily disturbed belts like Kuiper or singular through expectedly common ones like trojan 'belts'. (but will be very welcome if does!)

Other considerations and previous research

The model needs to fit only standard relatively usual scenarios: there happen to be the conditions that allow the formation of and asteroid belt but prevent it's accretion into a planet, (e.g., a Jovian around) but not any other strange condition (like gas planets drifting inwards in the formation period and altering significantly the distribution).

To be precise, I'd like to find out the most general of such expected distributions. If it's relevant o known, I'll be happy to have the distinct versions for the 'rocky' zone of the system, without volatiles, and the icy part.

I found an article about the distribution of asteroids in our main asteroid belt, but couldn’t get anything like what I ask from it: http://orbit.psi.edu/~tricaric/pdf/skads.pdf

Wikipedia also has something to say about it in the case of the Kuiper Belt: https://en.wikipedia.org/wiki/Kuiper_belt#Mass_and_size_distribution But as there seem to be so many things that do not fit the expected models about that belt, I don't dare make generalizations from it.

I understand that there won't be probably any accepted model of the kind I'm looking for, and giving an exact answer might involve doing original research, but I'd like to find out at least an acceptable and credible rule of thumb that has some decent foundation.

It's allowed that the diameter of the given asteroids is up to be enough to be considered planetoids (around 10^3 km), but if it's significantly bigger, please tell me how it does not clean it's orbit or form a 'trojan' type of ring instead of a typical more or less evenly spreaded ring, and I'll be happy to consider correct the 'magno-planetoids' :D.

Edit 1: Formatting changes and better parametrization of what's expected to be in and what may be left out of the answer.

Edit 2: I've found some interesting article: https://www-n.oca.eu/morby/papers/fossileSFD.pdf I'll post what I find in it as an answer if I'm able to get it from there, though it looks like it will only model our belt, and so not be enough.

  • $\begingroup$ Have you looked at JPL's Near-Earth Object Program? JPL generally has a lot of information on large and small bodies in the heliosphere. $\endgroup$ Mar 31, 2016 at 13:56
  • $\begingroup$ Thanx for the links and comment. I've been looking at around it, and i find it interesting. Though it does not answer the question, as it presents the Sol system 'experimental' data. I'm looking for models or general rules of thumb of size 'commonness' inside an asteroid belt, given n parameters. I'll edit the question to clarify that. $\endgroup$
    – Oxy
    Mar 31, 2016 at 17:04

1 Answer 1


This paper goes through the process of comparing a few models for size distribution of Kuiper Belt objects. The approach is much more empirical than what you seem to have in mind, but it does highlight that the size distribution is a power law, or a combination of multiple power laws.

Here is another paper which is also rather empirical, but discusses some theoretical implications for their observations and points out some relevant physical processes in star forming regions. This is before the formation of an individual asteroid belt or even proto-planetary disk, but similar processes may apply to the aggregation and destruction of dust/grains/pebbles in an asteroid belt.

As always in astrophysics, the answer is "it's (very) complicated", but hopefully that gives you a couple of hints to go on...

  • $\begingroup$ After many hours of messing with available papers, you end up confirming what I found... the only seemingly sure thing is that it can be defined somewhat by power laws. It's not that precise, but it fits my purposes nicely and gives me some creative freedom while still allowing me to have guidelines to keep everything scientifically plausible at least. $\endgroup$
    – Oxy
    Oct 7, 2016 at 10:58

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