<p>Brown dwarfs are technically stars, but not in your typical sense, as they cannot start or sustain nuclear fusion. Think about it this way: stars are formed in clumps inside giant gas clouds called nebulae, along with planets, but what if one of these clumps is too big to become a planet and too small to become red dwarfs. These are brown dwarfs. Some consider them to be stars, others consider them to be planets, and some neither. So, opinions vary.</p>

CC BY-SA 4.0
2023-01-13T16:11:26.513Z
No opinions, don't vary. Brown dwarfs and stars are mutually exclusive. Whilst there is a grey area between planets and brown dwarfs there is no such grey area between stars and brown dwarfs.
ProfRob
CC BY-SA 4.0
2019-04-01T06:41:31.983Z
2019-04-01T06:41:31.983Z
Samvart Upadhyay
<p>I was reading about the coolest stars, and was surprised to find about stars with a surface temperature lower than a candle, like 2MASS 0939-2448 A/B, of about 100 Celsius like CFBDSIR 1458+10B and even below 0 Celsius temperature where the water freezes like WISE J0855-0714. Then I thought, they might be stars where fusion only happens very deep in the core, and then I found out this:</p>
<p><a href="https://en.wikipedia.org/wiki/Brown_dwarf" rel="nofollow noreferrer">Brown dwarf</a></p>
<blockquote>
<p>In addition, many brown dwarfs undergo no fusion; those at the low end
of the mass range (under 13 MJ) are never hot enough to fuse even
deuterium, and even those at the high end of the mass range (over 60
MJ) cool quickly enough that after 10 million years they no longer
undergo fusion.</p>
</blockquote>
<p>Are these brown dwarfs which don't sustain any type of fusion considered stars? If so, what's the reason?</p>

CC BY-SA 4.0
2019-02-09T18:15:46.467Z
No, they're massive planets. Although there is some discussion in the scientific community at the moment where to draw the line between star and planet exactly, something that doesn't do fusion is no star for sure.
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-02-10T09:23:57.497Z
The book I am reading treats them as stars and made a distinction  to planet based on mechanism and dynamics of formation.  So as for the above comments it should be a grey area indeed. I could add a comment as soon I recover the book, I was right at cloud collapsing yesterday. Very roughly: collapse of  matter => stars.  Debris and dust collection => planets.
Alchimista
CC BY-SA 4.0
2019-02-10T21:47:44.957Z
You are confused. Just because they have a catalogue number, doesn't make them stars. They are brown dwarfs.
ProfRob
<star><brown-dwarf>
Are brown dwarfs which don't sustain any fusion considered stars?
Pablo
# Are brown dwarfs which don't sustain any fusion considered stars?

(Asked by: username_0 on 2019-02-09)

I was reading about the coolest stars, and was surprised to find about stars with a surface temperature lower than a candle, like 2MASS 0939-2448 A/B, of about 100 Celsius like CFBDSIR 1458+10B and even below 0 Celsius temperature where the water freezes like WISE J0855-0714. Then I thought, they might be stars where fusion only happens very deep in the core, and then I found out this:

[Brown dwarf](https://en.wikipedia.org/wiki/Brown_dwarf)

> In addition, many brown dwarfs undergo no fusion; those at the low end
> of the mass range (under 13 MJ) are never hot enough to fuse even
> deuterium, and even those at the high end of the mass range (over 60
> MJ) cool quickly enough that after 10 million years they no longer
> undergo fusion.

Are these brown dwarfs which don't sustain any type of fusion considered stars? If so, what's the reason?

**Tags:** star, brown-dwarf
> **Comments:**
> **username_1**: No, they're massive planets. Although there is some discussion in the scientific community at the moment where to draw the line between star and planet exactly, something that doesn't do fusion is no star for sure.  
> **username_2**: The book I am reading treats them as stars and made a distinction  to planet based on mechanism and dynamics of formation.  So as for the above comments it should be a grey area indeed. I could add a comment as soon I recover the book, I was right at cloud collapsing yesterday. Very roughly: collapse of  matter => stars.  Debris and dust collection => planets.  
> **username_3**: You are confused. Just because they have a catalogue number, doesn't make them stars. They are brown dwarfs.  

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## 1 answers

### Answer by username_4 on 2019-04-01. Score: 2

Brown dwarfs are technically stars, but not in your typical sense, as they cannot start or sustain nuclear fusion. Think about it this way: stars are formed in clumps inside giant gas clouds called nebulae, along with planets, but what if one of these clumps is too big to become a planet and too small to become red dwarfs. These are brown dwarfs. Some consider them to be stars, others consider them to be planets, and some neither. So, opinions vary.

> **Comments:**
> **username_3**: No opinions, don't vary. Brown dwarfs and stars are mutually exclusive. Whilst there is a grey area between planets and brown dwarfs there is no such grey area between stars and brown dwarfs.  

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