The discussion revolves around the cooling process of brown dwarfs, exploring how their temperature decreases over time and the implications of this cooling on their physical state. Participants examine various aspects, including the phase transitions of hydrogen, the role of gravity in heating, and comparisons to other celestial bodies like planets.
Participants do not reach a consensus on several points, including the mechanisms of cooling, the implications of gravitational energy, and the nature of phase transitions in brown dwarfs. Multiple competing views remain throughout the discussion.
Some statements rely on specific assumptions about the behavior of materials at low temperatures and the definitions of degeneracy pressure, which may not be universally accepted. The discussion also touches on the complexities of energy transfer and the physical states of matter in extreme conditions.
stefan r said:The word "death" has always bothered me with regard to stars. In what sense is a star "alive".
stefan r said:At low temperature the metals can precipitate and rain out of solution.
Would that actually happen - the raining out that is.stefan r said:At low temperature the metals can precipitate and rain out of solution. The falling droplets release energy because they are denser and they are falling down a gravity well. That will generate heat and delay surface cooling.
Electron degeneracy also holds up planets.256bits said:Would that actually happen - the raining out that is.
The brown dwarf is pretty dense already throughout, with electron degeneracy pressure holding it up, rather than kinetic motion of the protons.
I have no idea about Uranus.snorkack said:Electron degeneracy also holds up planets.
Three gas giants possesses internal heat - all except Uranus.
Would Uranus freeze at 1 bar level if it were in outer solar system?
Do you have a reference showing that it expands when it cools?Thecla said:The only fuel for heating a brown dwarf is gravity and gravity is eternal. This is where I get confused: The brown drawf cools by radiating heat, it cools off and expands. Then the cycle is repeated , it will contract due to gravity and heat up again. Why wouldn't this go on forever since you are not running out of gravity?
Thecla said:The only fuel for heating a brown dwarf is gravity and gravity is eternal. This is where I get confused: The brown drawf cools by radiating heat, it cools off and expands. Then the cycle is repeated , it will contract due to gravity and heat up again. Why wouldn't this go on forever since you are not running out of gravity?
I think we both are on about different parts of a brown dwarf life cycle.snorkack said:Would Uranus freeze at 1 bar level if it were in outer solar system?
No.256bits said:Planets are mainly supported from pressure produced by thermal motion of the atoms and molecules within.
Some degeneracy is present, but not to the extent of that within the dwarf stars, where the density is the deciding factor for its radius, regardless of temperature.
snorkack said:A bucket of water is supported by degeneracy. Trivial proof: cool it to absolute zero, at which thermal motion of atom and molecules witin does not exist. The contents of bucket expand when their thermal motion is stopped.
Planets are likewise degenerate, in that thermal expansion of the material has minor effects on total volume. And so are brown dwarfs.
What would you be meaning by that statement? Gravitational Potential Energy transfers to thermal energy which can the lost by radiation. That's not "eternal".Thecla said:gravity is eternal.
Hmm. Maybe you could say that but what counts here is Gravitational Potential Energy. That transfers partly to thermal energy, which radiates away and leaves less GPE. As the net energy goes down, so does the temperature.Thecla said:The only fuel for heating a brown dwarf is gravity and gravity is eternal.