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How long will the sun remain a white dwarf?



 
 
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  #11  
Old July 15th 07, 05:04 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar
Guy Macon
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Posts: 134
Default How long will the sun remain a white dwarf?




Paul Schlyter wrote:

At the start, the temperature difference is 100 deg C of course.
Let's say after one hour the temperature difference is 10 degrees.
After two hours it's 1 degree, after three hours 0.1 degrees, after
four hours 1E-2 degrees. After a day+night the temperature difference
is 1E-22 degrees, after a week 1E-166 degrees, after a year 1E-8764
degrees, and after 15 billion years 1E-131490000000000 degrees. The
temperature difference will never ever go all the way to zero!


This assumes that the quantum of temperature is smaller than
10^-131490000000000 degrees...

--
Guy Macon http://www.guymacon.com/

  #12  
Old July 15th 07, 05:55 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
[email protected]
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Posts: 23
Default How long will the sun remain a white dwarf?




Paul Schlyter wrote: (snip)

Paul please read the following references in order to
improve the quality of your posts::

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http://www.xs4all.nl/%7ewijnands/nnq/nquote.html

How do I quote correctly in usenet?
http://www.netmeister.org/news/learn2quote2.html

Common Mistakes in Usenet Postings and How to Avoid Them
http://www.complang.tuwien.ac.at/ant...s.html#quoting

Bottom vs. top posting and quotation style on Usenet
http://www.cs.tut.fi/~jkorpela/usenet/brox.html

Why bottom-posting is better than top-posting
http://www.caliburn.nl/topposting.html

+What do you mean "my reply is upside-down"?
http://www.i-hate-computers.demon.co.uk/quote.html

Put an end to Outlook Express's messy quotes with this automated fix!
http://home.in.tum.de/~jain/software/oe-quotefix/

  #13  
Old July 16th 07, 04:39 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
Crown-Horned Snorkack
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Default How long will the sun remain a white dwarf?

On 13 juuli, 22:45, Radium wrote:
Hi:

When the sun becomes a white dwarf, approximately how long will it
take for it to cool off to a cold black dwarf that does not emit
anymore heat or light [or other energies] than the surrounding space?

Thanks,

Radium


Would there ever be a time when the emitted heat of the white dwarf is
significantly less than incident relict radiation? The white dwarf is
cooling, but so is relict radiation...

  #14  
Old July 16th 07, 05:08 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
Chris L Peterson
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Default How long will the sun remain a white dwarf?

On Mon, 16 Jul 2007 08:39:07 -0700, Crown-Horned Snorkack
wrote:

Would there ever be a time when the emitted heat of the white dwarf is
significantly less than incident relict radiation? The white dwarf is
cooling, but so is relict radiation...


Unless you can propose some active cooling mechanism (that is, something
other than passive radiation), it would violate the second law of
thermodynamics for the white dwarf to become cooler than the temperature
of the Universe as measured from the white dwarf's location (which in
all likelihood will be very close to the average relict radiation
temperature).

The white dwarf will remain forever warmer than the background.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #15  
Old July 18th 07, 08:49 AM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
Crown-Horned Snorkack
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Default How long will the sun remain a white dwarf?

On 16 juuli, 19:08, Chris L Peterson wrote:
On Mon, 16 Jul 2007 08:39:07 -0700, Crown-Horned Snorkack

wrote:
Would there ever be a time when the emitted heat of the white dwarf is
significantly less than incident relict radiation? The white dwarf is
cooling, but so is relict radiation...


Unless you can propose some active cooling mechanism (that is, something
other than passive radiation), it would violate the second law of
thermodynamics for the white dwarf to become cooler than the temperature
of the Universe as measured from the white dwarf's location (which in
all likelihood will be very close to the average relict radiation
temperature).

The white dwarf will remain forever warmer than the background.

And Earth is forever warmer than background. However, geothermal heat
is negligible compared to incident light of Sun.

Would the white dwarf cool to a point where its loss of internal heat
is smaller than the incident relict radiation?

  #16  
Old July 18th 07, 02:59 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
Passing through [email protected]
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Default How long will the sun remain a white dwarf?

On Fri, 13 Jul 2007 19:45:36 -0000, Radium
wrote:

Hi:

When the sun becomes a white dwarf, approximately how long will it
take for it to cool off to a cold black dwarf that does not emit
anymore heat or light [or other energies] than the surrounding space?


Thanks,

Radium


Hasn't the recent discovery that the Universe's expanse is
accelerating put an upper limit on the lifetime of the Unverse? Or at
least the lifetime before every particle is froced apart from al te
particles? Of course I'm sure that with in another 20 years someone
will make another discovery which will throw that model out as well.
  #18  
Old July 18th 07, 03:34 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
Chris L Peterson
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Posts: 10,007
Default How long will the sun remain a white dwarf?

On Wed, 18 Jul 2007 00:49:53 -0700, Crown-Horned Snorkack
wrote:

And Earth is forever warmer than background. However, geothermal heat
is negligible compared to incident light of Sun.


Not so. The Earth gives up more heat than it receives from the Sun. It
is slowly cooling. The Sun provides nowhere near enough energy to heat
the Earth above its current temperature. Don't confuse the temperature
of the Earth as a whole, which is determined by residual heat of
formation and by internal radioactive processes, with the surface and
atmospheric temperature, which is determined largely by solar radiation.

Would the white dwarf cool to a point where its loss of internal heat
is smaller than the incident relict radiation?


Again, that would violate the second law. Heat flows from warm to cold,
not the other way. The white dwarf will spend eternity with its
temperature asymptotically approaching its surrounding temperature. It
can never get colder than the background, unless some cosmic
refrigerator comes along and actively pumps heat out of it.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #19  
Old July 20th 07, 10:12 AM posted to sci.astro.amateur,sci.astro,alt.astronomy,alt.astronomy.solar,uk.sci.astronomy
Paul Schlyter[_2_]
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Posts: 893
Default How long will the sun remain a white dwarf?

In article ,
Chris L Peterson wrote:

On Wed, 18 Jul 2007 00:49:53 -0700, Crown-Horned Snorkack
wrote:

And Earth is forever warmer than background. However, geothermal heat
is negligible compared to incident light of Sun.


Not so. The Earth gives up more heat than it receives from the Sun. It
is slowly cooling. The Sun provides nowhere near enough energy to heat
the Earth above its current temperature. Don't confuse the temperature
of the Earth as a whole, which is determined by residual heat of
formation and by internal radioactive processes, with the surface and
atmospheric temperature, which is determined largely by solar radiation.


.....which means the geothermal heat flow is negligible compared to
the radiation heat flow from the Sun onto the Earth, and from the Earth
out into speace. Or else, geothermal heat would need to be taken into
account by meteorologists when forecasting the weather.

Only on small parts of the Earth (e.g. on Iceland), geothermal heat flow
is non-negligible on the Earth's surface.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
 




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