<p><strong>Attempt to do an intuitive explanation:</strong></p>

<p>The Sun was formed from a cloud of matter. A small amount of that matter remained around the Sun, and had a similar composition. This was the solar nebulae.</p>

<p>But the composition of the planets are now not the same as the Sun. This is explained by that some of the matter was collected by the Sun, and some of it was blown out of the system.</p>

<p><strong>That was only the light stuff!</strong> like hydrogen and helium. Most iron and other metals are conjectured to have remained in orbit, forming the planets.</p>

<p>As the Sun is representative for the original composition (partly at least, stellar fusion has skewed the hydrogen/helium ratio). So if iron is 0.14% of the Sun, that is also the original abundance in the nebulae. <strong>So all the iron in the planetary bodies is 0.14% of the original nebulae mass</strong>.</p>

<p>From that you can calculate the original mass. It is a 'minimum' because some of the iron may have escaped as well.</p>

CC BY-SA 3.0
2016-02-15T15:56:57.537Z
Thanks for your reply! So to calculate the MMSN, I'd say that (for the rocky planets inside the snow line), if I know their masses and I know metals are 2% of the solar abundance, I can say that the sum of the masses of the rocky planets is x, and that the nebulae must have had 50 times as much material?
Stacks of overflow
CC BY-SA 3.0
2016-02-15T16:12:30.037Z
@Stacksofoverflow That is correct! 50 times is a *minimum* though, as some of the metals may have been lost too.
SE - stop firing the good guys
CC BY-SA 3.0
2016-02-15T16:16:56.780Z
Awesome, thanks so much. But now what if I'm looking at the planets outside of the snow line, would I assume that they are gas giants and so assume that their masses are only off by 2%? (Based on those assumptions?) Or would I have to try and find data on their cores?
Stacks of overflow
CC BY-SA 3.0
2016-02-15T16:19:32.727Z
@Stacksofoverflow You have found one of the basic limitations of the MMSN. We do not actually now a lot of the size nor the composition of the gas giant cores, so that gives a lot of uncertainty.
SE - stop firing the good guys
CC BY-SA 3.0
2016-02-15T16:22:30.450Z
Interesting, so in that case, when constructing the MMSN, how do astronomers scale for the masses of these planets?
Stacks of overflow
CC BY-SA 3.0
2016-02-15T16:26:17.830Z
@Stacksofoverflow Do not tell anyone this big secret, but a lot of things in astronomy is based upon inaccurate numbers and educated guesses. I can see if I can add more detail to my answer as soon as possible.
SE - stop firing the good guys
CC BY-SA 3.0
2016-02-15T16:30:51.710Z
alright, thanks for the conversation. I'm realizing that educated guesses and inaccurate measurements is the standard as I move along, lol.
Stacks of overflow
CC BY-SA 3.0
2016-02-15T12:07:06.160Z
2016-02-15T12:42:49.137Z
2016-02-15T12:42:49.137Z
SE - stop firing the good guys
<p>I'm attempting to build a MMSN, I've been trying for about... a week to get an intuition on the scaling factors for calculating the mass of the disks, I'm not entirely sure how to think about it. I feel as if the concept is extremely simple but that I'm thinking of it incorrectly. Can someone explain what exactly these scaling factors account for and how one would calculate them? I'm not looking for a solution, I'm looking for intuition on how these scaling factors are found. </p>

<p>My understand is that you pick an element, (Fe), and compare that to the solar abundance (does this mean the abundance of Fe in the sun? From there I would look at the abundance of Fe in the cores of the planet and compare them somehow to get some sort of scaling factor. From what I understand Fe makes .14% of the suns mass, so if I know lets say that neptune has a mass of 17m(earth) how would I start finding the scaling factor. </p>

<p>Thanks! </p>

CC BY-SA 3.0
2016-02-15T08:32:59.320Z
I can't understand this question, though it sounds of interest.
ProfRob
<mass><accretion-discs><the-sun>
Minimum Mass Solar Nebulae Scaling Factors
Stacks of overflow
# Minimum Mass Solar Nebulae Scaling Factors

(Asked by: username_0 on 2016-02-14)

I'm attempting to build a MMSN, I've been trying for about... a week to get an intuition on the scaling factors for calculating the mass of the disks, I'm not entirely sure how to think about it. I feel as if the concept is extremely simple but that I'm thinking of it incorrectly. Can someone explain what exactly these scaling factors account for and how one would calculate them? I'm not looking for a solution, I'm looking for intuition on how these scaling factors are found.

My understand is that you pick an element, (Fe), and compare that to the solar abundance (does this mean the abundance of Fe in the sun? From there I would look at the abundance of Fe in the cores of the planet and compare them somehow to get some sort of scaling factor. From what I understand Fe makes .14% of the suns mass, so if I know lets say that neptune has a mass of 17m(earth) how would I start finding the scaling factor.

Thanks!

**Tags:** mass, accretion-discs, the-sun
> **Comments:**
> **username_1**: I can't understand this question, though it sounds of interest.  

---

## 1 answers

### Answer by username_2 on 2016-02-15. Score: 1 | Accepted answer

**Attempt to do an intuitive explanation:**

The Sun was formed from a cloud of matter. A small amount of that matter remained around the Sun, and had a similar composition. This was the solar nebulae.

But the composition of the planets are now not the same as the Sun. This is explained by that some of the matter was collected by the Sun, and some of it was blown out of the system.

**That was only the light stuff!** like hydrogen and helium. Most iron and other metals are conjectured to have remained in orbit, forming the planets.

As the Sun is representative for the original composition (partly at least, stellar fusion has skewed the hydrogen/helium ratio). So if iron is 0.14% of the Sun, that is also the original abundance in the nebulae. **So all the iron in the planetary bodies is 0.14% of the original nebulae mass**.

From that you can calculate the original mass. It is a 'minimum' because some of the iron may have escaped as well.

> **Comments:**
> **username_0**: Thanks for your reply! So to calculate the MMSN, I'd say that (for the rocky planets inside the snow line), if I know their masses and I know metals are 2% of the solar abundance, I can say that the sum of the masses of the rocky planets is x, and that the nebulae must have had 50 times as much material?  
> **username_2**: @Stacksofoverflow That is correct! 50 times is a *minimum* though, as some of the metals may have been lost too.  
> **username_0**: Awesome, thanks so much. But now what if I'm looking at the planets outside of the snow line, would I assume that they are gas giants and so assume that their masses are only off by 2%? (Based on those assumptions?) Or would I have to try and find data on their cores?  
> **username_2**: @Stacksofoverflow You have found one of the basic limitations of the MMSN. We do not actually now a lot of the size nor the composition of the gas giant cores, so that gives a lot of uncertainty.  
> **username_0**: Interesting, so in that case, when constructing the MMSN, how do astronomers scale for the masses of these planets?  
> **username_2**: @Stacksofoverflow Do not tell anyone this big secret, but a lot of things in astronomy is based upon inaccurate numbers and educated guesses. I can see if I can add more detail to my answer as soon as possible.  
> **username_0**: alright, thanks for the conversation. I'm realizing that educated guesses and inaccurate measurements is the standard as I move along, lol.  

---

