<p>The Oort Cloud has not been observed directly so far, so it's really hard to make any statement about its nature. That said, if the Asteroid Belt is anything to go by, we can maybe make some sort of estimate.</p>
<p><a href="https://www.researchgate.net/figure/Size-frequency-distributions-of-asteroids-in-near-Earth-orbits-and-the-main-belt-Bottke_fig2_351020644" rel="nofollow noreferrer">This chart</a> shows that models of the main asteroid belt predict that it contains on the order of 10^7 (10 million) asteroids 1 km in diameter, 10^9 (1 billion) objects 100 meters wide, and 10^11 (100 billion) objects 10 meters across.</p>
<p><a href="https://i.sstatic.net/pBNGj8Gf.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/pBNGj8Gf.png" alt="Chart of estimated asteroid count by diameter" /></a></p>
<p>If we assume the Oort cloud exists and follows that same distribution (not a well supported assumption!), then we should very approximately expect the density of objects to go up by two orders of magnitude for each order of magnitude we go down in size (i.e. objects 1/10th as large should be roughly 100 times more dense), so no, linear wouldn't work there.</p>

CC BY-SA 4.0
2024-11-13T16:32:20.923Z
Well, maybe not such a bad assumption, since the Oort cloud did form in the inner Solar System and then was scattered out. But of course the scattering might have been size dependent...?
ProfRob
CC BY-SA 4.0
2024-11-13T16:44:17.330Z
It could also depend on material, the asteroid belt is basically rocky but the oort is supposed to be much more ice-heavy and that could change how it developed. (Mostly thinking of small objects being subject to sublimation or some such thing, at least if they get warm enough.)
Darth Pseudonym
CC BY-SA 4.0
2024-11-14T10:56:40.600Z
That is a very good point about size distribution, one which would have to be taken into account, as would another assumption about the Oort cloud being centrally condensed.
Wookie
CC BY-SA 4.0
2024-11-13T15:56:04.217Z
2024-11-13T15:56:04.217Z
Darth Pseudonym
<p>Astronomy magazine (<a href="https://www.astronomy.com/science/ive-heard-that-the-oort-cloud-contains-trillions-of-icy-bodies-what-would-be-the-average-distance-between-these-bodies/" rel="nofollow noreferrer">here)</a> has stated the following:</p>
<blockquote>
<p>The Oort Cloud has many more objects than the main asteroid belt, some trillion objects larger than a kilometer, but it also occupies a much larger volume of space from 5,000 AU to beyond 20,000 to 50,000 AU from the Sun. Oort Cloud objects larger than 1 km have some 31 million miles (50 million km) between each other. This is about the distance between Earth and Mars at their closest approach.</p>
</blockquote>
<p>I assume that in its creationary phase the cloud contained objects smaller than 1km and that occasional collisions continue to produce smaller objects. Would it be a ridiculous approach to linearly scale down the separational distance by size, saying that (for example) objects of 1 m have 50 thousand km between them and objects of 1 mm have 1 thousand km between them?</p>

CC BY-SA 4.0
2024-11-12T15:01:22.777Z
Even this 50 million km for +1 km is a ballpark estimate, to put it mildly.
Mithoron
CC BY-SA 4.0
2024-11-12T23:09:14.130Z
Please bear in mind that the Oort cloud is still hypothetical. We *assume* it exists, and that occasionally comets come from there, but we can't see it, and we can't detect any gravitational effects from Oort cloud bodies.
PM 2Ring
CC BY-SA 4.0
2024-11-13T15:54:00.593Z
Hold on. Your source says 50 million km is the estimated distance between objects "larger than" 1 km, which isn't the same as saying "objects of 1 km diameter". Even if the linear approach worked, which is probably doesn't, you aren't going linearly.
Darth Pseudonym
<asteroids><distances><collision>
What are the relative distances between objects in the Oort cloud?
Wookie
# What are the relative distances between objects in the Oort cloud?

(Asked by: username_0 on 2024-11-12)

Astronomy magazine ([here)](https://www.astronomy.com/science/ive-heard-that-the-oort-cloud-contains-trillions-of-icy-bodies-what-would-be-the-average-distance-between-these-bodies/) has stated the following:

> The Oort Cloud has many more objects than the main asteroid belt, some trillion objects larger than a kilometer, but it also occupies a much larger volume of space from 5,000 AU to beyond 20,000 to 50,000 AU from the Sun. Oort Cloud objects larger than 1 km have some 31 million miles (50 million km) between each other. This is about the distance between Earth and Mars at their closest approach.

I assume that in its creationary phase the cloud contained objects smaller than 1km and that occasional collisions continue to produce smaller objects. Would it be a ridiculous approach to linearly scale down the separational distance by size, saying that (for example) objects of 1 m have 50 thousand km between them and objects of 1 mm have 1 thousand km between them?

**Tags:** asteroids, distances, collision
> **Comments:**
> **username_1**: Even this 50 million km for +1 km is a ballpark estimate, to put it mildly.  
> **username_2**: Please bear in mind that the Oort cloud is still hypothetical. We *assume* it exists, and that occasionally comets come from there, but we can't see it, and we can't detect any gravitational effects from Oort cloud bodies.  
> **username_3**: Hold on. Your source says 50 million km is the estimated distance between objects "larger than" 1 km, which isn't the same as saying "objects of 1 km diameter". Even if the linear approach worked, which is probably doesn't, you aren't going linearly.  

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## 1 answers

### Answer by username_3 on 2024-11-13. Score: 3 | Accepted answer

The Oort Cloud has not been observed directly so far, so it's really hard to make any statement about its nature. That said, if the Asteroid Belt is anything to go by, we can maybe make some sort of estimate.

[This chart](https://www.researchgate.net/figure/Size-frequency-distributions-of-asteroids-in-near-Earth-orbits-and-the-main-belt-Bottke_fig2_351020644) shows that models of the main asteroid belt predict that it contains on the order of 10^7 (10 million) asteroids 1 km in diameter, 10^9 (1 billion) objects 100 meters wide, and 10^11 (100 billion) objects 10 meters across.

[![Chart of estimated asteroid count by diameter](https://i.sstatic.net/pBNGj8Gf.png)](https://i.sstatic.net/pBNGj8Gf.png)

If we assume the Oort cloud exists and follows that same distribution (not a well supported assumption!), then we should very approximately expect the density of objects to go up by two orders of magnitude for each order of magnitude we go down in size (i.e. objects 1/10th as large should be roughly 100 times more dense), so no, linear wouldn't work there.

> **Comments:**
> **username_4**: Well, maybe not such a bad assumption, since the Oort cloud did form in the inner Solar System and then was scattered out. But of course the scattering might have been size dependent...?  
> **username_3**: It could also depend on material, the asteroid belt is basically rocky but the oort is supposed to be much more ice-heavy and that could change how it developed. (Mostly thinking of small objects being subject to sublimation or some such thing, at least if they get warm enough.)  
> **username_0**: That is a very good point about size distribution, one which would have to be taken into account, as would another assumption about the Oort cloud being centrally condensed.  

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