<p>To explain the high C/O and HCN/H<span class="math-container">$_2$</span>O ratios in the inner region of brown dwarf circumstellar disks the authors of the article mentioned (arxiv.org/pdf/1311.1228) deduce that the icy planetesimals beyond the snow line are not migrating inwards around brown dwarfs.  In larger planetary disks icy planetesimals migrate inward and supplement the water within the snow line.  Migration is probably not effective in Brown Dwarf disks because the gas density is too low.  They also speculate that the formation rate of icy planetesimals is more efficient in the smaller disks.  The lines they measure indicate temperatures above 600 C so they are selectively measuring the chemistry only in the inner parts of disks.</p>
<p>Most of the oxygen in a disk binds with the plentiful amount of hydrogen so with less water there is less oxygen and a higher C/O ratio.</p>
<p>The Earth formed within the snow line where water remains gaseous in the planetary disk, so our water came from planetesimals or comets from beyond the snow line.</p>

CC BY-SA 4.0
2024-09-28T07:36:30.790Z
The authors of which article?
ProfRob
CC BY-SA 4.0
2024-09-28T14:28:10.120Z
arxiv.org/pdf/1311.1228 mentioned in the comments.
eshaya
CC BY-SA 4.0
2024-09-26T16:52:21.167Z
2024-09-28T14:28:06.810Z
2024-09-28T14:28:06.810Z
eshaya
<p>I was reading into brown dwarf systems and I heard that most planets orbiting one would mostly be depleted of water and be carbon planets, though it never gave an answer as to why. Jupiter and it's moons are rich in water and water ice, and a brown dwarf is only a few times more massive, so why are their satellites/planets so different? Is it due to their formation method or something else?</p>

CC BY-SA 4.0
2024-09-24T20:26:06.183Z
Better with a citation to where this is claimed or discussed.
ProfRob
CC BY-SA 4.0
2024-09-25T04:01:35.500Z
On page 23 of https://arxiv.org/pdf/1311.1228 it says that the inner regions of brown dwarf disks are drier than  t  tauri disks and the composition of rocky planets around brown dwarfs should include large amounts of carbon.
sno
<star-formation><planetary-formation><brown-dwarf>
Why are brown dwarf systems commonly carbon planets?
ArchiveOfStars
# Why are brown dwarf systems commonly carbon planets?

(Asked by: username_0 on 2024-09-24)

I was reading into brown dwarf systems and I heard that most planets orbiting one would mostly be depleted of water and be carbon planets, though it never gave an answer as to why. Jupiter and it's moons are rich in water and water ice, and a brown dwarf is only a few times more massive, so why are their satellites/planets so different? Is it due to their formation method or something else?

**Tags:** star-formation, planetary-formation, brown-dwarf

> **Comments:**
> **username_1**: Better with a citation to where this is claimed or discussed.  
> **username_2**: On page 23 of https://arxiv.org/pdf/1311.1228 it says that the inner regions of brown dwarf disks are drier than  t  tauri disks and the composition of rocky planets around brown dwarfs should include large amounts of carbon.  

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## 1 answers

### Answer by username_3 on 2024-09-26. Score: 2 | Accepted answer

To explain the high C/O and HCN/H$\_2$O ratios in the inner region of brown dwarf circumstellar disks the authors of the article mentioned (arxiv.org/pdf/1311.1228) deduce that the icy planetesimals beyond the username_2w line are not migrating inwards around brown dwarfs. In larger planetary disks icy planetesimals migrate inward and supplement the water within the username_2w line. Migration is probably not effective in Brown Dwarf disks because the gas density is too low. They also speculate that the formation rate of icy planetesimals is more efficient in the smaller disks. The lines they measure indicate temperatures above 600 C so they are selectively measuring the chemistry only in the inner parts of disks.

Most of the oxygen in a disk binds with the plentiful amount of hydrogen so with less water there is less oxygen and a higher C/O ratio.

The Earth formed within the username_2w line where water remains gaseous in the planetary disk, so our water came from planetesimals or comets from beyond the username_2w line.

> **Comments:**
> **username_1**: The authors of which article?  
> **username_3**: arxiv.org/pdf/1311.1228 mentioned in the comments.  

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