<p>A &quot;star&quot; has significant hydrogen fusion occuring in its core.  This energy prevents collapse and allows the star to reach a stable position state.</p>
<p>A Brown dwarf does not have significant hydrogen fusion.  Its core is heated by the release of gravitational energy (the Kelvin–Helmholtz mechanism).</p>
<p>The transition between brown and red dwarfs is at around 80 Jupiter masses. At the transition it can be hard to distinguish brown and red dwarfs, especially when they are young. It may not be possible to tell the difference between a young star at 85 Jupiter masses, and a young brown dwarf at 75.</p>

CC BY-SA 4.0
2021-08-22T05:58:58.037Z
Nice answer. Do you know whether these transition stars would appear with starspots and granules or with  bands?
Prallax
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2021-08-21T17:51:31.897Z
2021-08-21T17:51:31.897Z
James K
<p>I've generally seen brown dwarfs depicted as more massive and slightly wider Jupiters in varying colors with banded cloud structures, sometimes hot enough to be visible glowing. I've also seen red dwarfs generally depicted as smaller and redder suns with sunspots and granules, and Wikipedia <a href="https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems#Variability" rel="nofollow noreferrer">mentions</a> that red dwarfs are prone to large starspots and flares. My question is where is the transition region between them and what happens there? Can there be brown dwarfs with starspots? Red dwarfs with bands?</p>

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2021-08-21T10:44:51.860Z
sometimes it may be difficult to distinguish a brown dwarf from a low mass star. Have a look at this wonderful answer about the lithium test https://astronomy.stackexchange.com/questions/20698/concerning-the-lithium-test-for-brown-dwarfs/20740#20740
Prallax
<planetary-atmosphere><brown-dwarf><surface><red-dwarf><stellar-atmospheres>
At what point does an astronomical body's surface stop being gas giant-like and start being sun-like?
Adam Lincoln Steele
# At what point does an astronomical body's surface stop being gas giant-like and start being sun-like?

(Asked by: username_0 on 2021-08-21)

I've generally seen brown dwarfs depicted as more massive and slightly wider Jupiters in varying colors with banded cloud structures, sometimes hot enough to be visible glowing. I've also seen red dwarfs generally depicted as smaller and redder suns with sunspots and granules, and Wikipedia [mentions](https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems#Variability) that red dwarfs are prone to large starspots and flares. My question is where is the transition region between them and what happens there? Can there be brown dwarfs with starspots? Red dwarfs with bands?

**Tags:** planetary-atmosphere, brown-dwarf, surface, red-dwarf, stellar-atmospheres

> **Comments:**
> **username_1**: sometimes it may be difficult to distinguish a brown dwarf from a low mass star. Have a look at this wonderful answer about the lithium test https://astronomy.stackexchange.com/questions/20698/concerning-the-lithium-test-for-brown-dwarfs/20740#20740  

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## 1 answers

### Answer by username_2 on 2021-08-21. Score: 2

A "star" has significant hydrogen fusion occuring in its core. This energy prevents collapse and allows the star to reach a stable position state.

A Brown dwarf does not have significant hydrogen fusion. Its core is heated by the release of gravitational energy (the Kelvin–Helmholtz mechanism).

The transition between brown and red dwarfs is at around 80 Jupiter masses. At the transition it can be hard to distinguish brown and red dwarfs, especially when they are young. It may not be possible to tell the difference between a young star at 85 Jupiter masses, and a young brown dwarf at 75.

> **Comments:**
> **username_1**: Nice answer. Do you know whether these transition stars would appear with starspots and granules or with  bands?  

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