<p>In one stage of classic accretion, the mass growth rate with time (dm/dt) for individual planetesimals is proportional to <span class="math-container">$m^{2/3}$</span> and in another stage it is proportional to <span class="math-container">$m^{4/3}$</span>.
My question is why are the exponents different? Which stage is a runaway and which stage comes first?</p>

CC BY-SA 4.0
2020-06-12T17:51:37.343Z
There are different theories of planetesimal formation - can you clarify where you are finding these relations, and more about what that source says about what the different stages are?
Eric Jensen
CC BY-SA 4.0
2020-12-22T18:50:11.547Z
Some superficial knowledge of differentiation is sufficient to conclude that solutions blow up in finite time for *m* in the 4/3 power and grow indefinitely as time cubed for *m* in the 2/3 power.
Incnis Mrsi
<astrophysics>
Question about mass growth rate for individual planetesimals
Boris
# Question about mass growth rate for individual planetesimals

(Asked by: username_0 on 2020-06-12)

In one stage of classic accretion, the mass growth rate with time (dm/dt) for individual planetesimals is proportional to $m^{2/3}$ and in another stage it is proportional to $m^{4/3}$.
My question is why are the exponents different? Which stage is a runaway and which stage comes first?

**Tags:** astrophysics

> **Comments:**
> **username_1**: There are different theories of planetesimal formation - can you clarify where you are finding these relations, and more about what that source says about what the different stages are?  
> **username_2**: Some superficial knowledge of differentiation is sufficient to conclude that solutions blow up in finite time for *m* in the 4/3 power and grow indefinitely as time cubed for *m* in the 2/3 power.  

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## 0 answers

