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Brown Dwarfs ???



 
 
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  #1  
Old June 12th 07, 10:19 PM posted to alt.astronomy
G=EMC^2 Glazier[_1_]
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Default Brown Dwarfs ???

They are not a planet. They are not a star What is the best
definition used to describe them? Is Jupiter a brown dwarf? It does not
look brown. Black dwarfs are a white dwarf that has cooled to a point
it no longer gives off heat(I think???) Bert

  #5  
Old June 16th 07, 02:52 AM posted to alt.astronomy
Scott Miller
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Default Brown Dwarfs ???

G=EMC^2 Glazier wrote:
They are not a planet. They are not a star What is the best
definition used to describe them? Is Jupiter a brown dwarf? It does not
look brown. Black dwarfs are a white dwarf that has cooled to a point
it no longer gives off heat(I think???) Bert


They are simply clumps of matter that failed to sustain nuclear fusion
as an energy source. Jupiter does not qualify because it is about 100
times too light to generate the temperatures and densities at its core
to initiate, let alone sustain nuclear fusion.
  #6  
Old June 16th 07, 12:19 PM posted to alt.astronomy
G=EMC^2 Glazier[_1_]
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Default Brown Dwarfs ???

Scott Brown is kind of close to the color red.,so can I think of a
brown dwarf evolving in time from a red dwarf? I 'm not confusing them
with a "real" red dwarf that can shine for a longer period than the Sun.
It is written it would take the mass of 80 Jupiters to create a core
that would light the fire of fusion bert

  #7  
Old June 16th 07, 12:30 PM posted to alt.astronomy
Scott Miller
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Default Brown Dwarfs ???

G=EMC^2 Glazier wrote:
Scott Brown is kind of close to the color red.,so can I think of a
brown dwarf evolving in time from a red dwarf? I 'm not confusing them
with a "real" red dwarf that can shine for a longer period than the Sun.
It is written it would take the mass of 80 Jupiters to create a core
that would light the fire of fusion bert


When is a red dwarf not a red dwarf. We are very precise in our
language in science, so saying that a brown dwarf evolved from a red
dwarf that is not a real red dwarf makes no sense.

A red dwarf maintains nuclear fusion in its core, a brown dwarf does
not. The transition between one or the other is in the amount of mass
each has to create the conditions in the core for fusion to either begin
and be sustained, or possibly begin and stop, if begin at all.
  #8  
Old June 16th 07, 12:57 PM posted to alt.astronomy
Tom Kerr
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Default Brown Dwarfs ???

In article , Scott Miller wrote:
G=EMC^2 Glazier wrote:
They are not a planet. They are not a star What is the best
definition used to describe them? Is Jupiter a brown dwarf? It does not
look brown. Black dwarfs are a white dwarf that has cooled to a point
it no longer gives off heat(I think???) Bert


They are simply clumps of matter that failed to sustain nuclear fusion
as an energy source. Jupiter does not qualify because it is about 100
times too light to generate the temperatures and densities at its core
to initiate, let alone sustain nuclear fusion.


Jupiter is not a brown dwarf, but what you state is incorrect. You can go
as low as 13 Jupiter masses and get deuterium burning (which is fusion),
and objects with 60 to 70 Jupiter masses or more burn both deuterium and
lithium.


  #9  
Old June 16th 07, 03:06 PM posted to alt.astronomy
G=EMC^2 Glazier[_1_]
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Default Brown Dwarfs ???

Scott It is tricky but I read there are two types of red dwarfs. Maybe
an astronomer would be best to define the two for us? bert

  #10  
Old June 16th 07, 03:14 PM posted to alt.astronomy
G=EMC^2 Glazier[_1_]
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Posts: 10,860
Default Brown Dwarfs ???

Tom I think I should have read your post before answering Scott. What
you posted gives the reason for the type of red dwarf were talking
about. Thanks for clearing it up. One has fusion for a short time the
other red dwarf evolved from a massive star and will radiate for a long
time bert

 




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