How long will the sun remain a white dwarf?

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

Radium wrote:
>
> 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?
>

The Cooling of CO White Dwarfs: Influence of the Internal Chemical Distribution
http://www.journals.uchicago.edu/ApJ...903/34903.html

On Fri, 13 Jul 2007 19:45:36 -0000, Radium <glucegen1@gmail.com> 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?

That would take forever. But a few tens of billions of years should be
long enough that the temperature drops low enough that no photons in the
visible range are produced, which is generally what defines a black
dwarf.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Jul 13, 1:16 pm, Chris L Peterson <c...@alumni.caltech.edu> wrote:

> That would take forever. But a few tens of billions of years should be
> long enough that the temperature drops low enough that no photons in the
> visible range are produced, which is generally what defines a black
> dwarf.

Approximately how long until this white drawf [which used to be the
sun] cools to around 70 degrees Fahrenheit? Will the universe exist
long enough for this to happen?

Radium wrote:
> On Jul 13, 1:16 pm, Chris L Peterson <c...@alumni.caltech.edu> wrote:
>
>> That would take forever. But a few tens of billions of years should be
>> long enough that the temperature drops low enough that no photons in the
>> visible range are produced, which is generally what defines a black
>> dwarf.
>
> Approximately how long until this white drawf [which used to be the
> sun] cools to around 70 degrees Fahrenheit? Will the universe exist
> long enough for this to happen?
>

The Cooling of CO White Dwarfs: Influence of the Internal Chemical Distribution
http://www.journals.uchicago.edu/ApJ...903/34903.html

On Fri, 13 Jul 2007 21:42:41 -0700, Radium <glucegen1@gmail.com> wrote:

>Approximately how long until this white drawf [which used to be the
>sun] cools to around 70 degrees Fahrenheit? Will the universe exist
>long enough for this to happen?

The temperature falls off somewhat exponentially... looks like it would
take hundreds of billions of years to get that cool, maybe trillions.
But it has all the time in the world (or the Universe), since it seems
likely the Universe will not ever cease to exist, but will just keep
cooling down and expanding forever.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Fri, 13 Jul 2007 19:45:36 -0000, Radium <glucegen1@gmail.com>
wrote:

>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?

It takes a solar type star about 100 billion years, which is more than
the presently estimated age of the universe.

Bud
--
The night is just the shadow of the Earth.

In article <1184355936.720567.167930@o11g2000prd.googlegroups .com>,
Radium <glucegen1@gmail.com> wrote:

> 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?

SInce the cooloff is pretty much exponential, it will take forever and
the rediated energy will never drop to exactly zero. SO you should
rephrase your question as:

# 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
# any significant anounts of heat or light [or other energies] than
# the surrounding space?

That time span will depend a lot on your precise definition of
"significant". But it will probably take hundreds of billion years,
or more.

Let me give you one concrete example: suppose the outside temperature
is exactly freezing, i.e. 0 deg C. You boil a pot of water, then
bring it outside. How long time will it take until the pot has
cooled down so there's no temperature difference between the pot
of water and the surroundings?

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!

Of course a temperature difference of 1E-6 degrees or smaller is
indistinguishable from zero - we call such a difference insignificant.

But where do you draw the line between "significant" and
"insignificant" here? In the example above, do you consider the
temperature of the pot of water to be "the same" as the surroundings
when the temperature difference drops below one degree? If so, it
will happen after two hours. Or do you require a temperature
difference of less than 0.01 degrees to consider the temperatures "the
same"? If so, the cooldown will require four hours.

The situation is similar with a white dwarf: no internal fusion gives
any energy anymore, so the white dwarf just cools down. OK, there's
one internal energy source remaining: gravitational contraction: the
white dwarf can contract somewhat under its own gravitation, and that
will release some energy, keeping it warmer for some time(*). But
still the white dwarf cools off more or less exponentially. Now,
since the white dwarfs are faint stars, they don't radiate that much
energy out into space, and that's one major reason they can "live" for
so long.

(*) Before astronomer's realized that the Sun's energy source was nuclear
fusion, other sources of energy were suggested. If the Sun had been
a huge coal fire, it would be able to shine only for a few centuries,
maybe a millennium. A more efficient energy source was gravitational
contraction, which would be able to keep the Sun hot for approximately
a million years. Back then, geologists suggesting that the Earth is
some 5 billion years old had an obvious difficulty: what energy source
could have kept the Sun shining for those five billion years? The
answer is of course nuclear fusion - but it wasn't until well into the
1900's that astronomers realized this.

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

In article <d2nf9391k03rnq48ejansavkuqltrgipdq@4ax.com>,
Chris L Peterson <clp@alumni.caltech.edu> wrote:

> On Fri, 13 Jul 2007 19:45:36 -0000, Radium <glucegen1@gmail.com> 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?
>
> That would take forever. But a few tens of billions of years should be
> long enough that the temperature drops low enough that no photons in the
> visible range are produced, which is generally what defines a black
> dwarf.

That would take forever too!!! According to the Planck blackbody
radiation curve, any blackbody hotter than absolute zero radiates
photons over all wavelengths. Yes, you and I radiate visible light,
X-rays and even gamma rays, although at an extremely low rate - but
still at a rate slightly above zero. And if a cool body would emit,
say, one gamma ray photon over a billion years, is that "no gamma
radiation" or not?

So if you say "that would take forever" about cooling down until no
more energy is radiated, you must say the same about radiation at
visible wavelengths, or any other wavelength rate. Only if you set some
level near but above sero as "insignificant" you can assign a finite
cooldown time span.

>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

On Sat, 14 Jul 2007 09:42:19 GMT, pausch@saaf.se (Paul Schlyter) wrote:

>That would take forever too!!!

That's true. I meant until the level of visible photons drops below
detectability (which is, of course, a moving target). As you say, all
that can be done is to set a threshold, or a specific target
temperature.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Don'tforget about fluctuation theory, sometimes known as Statistical
Mechanics. You will et a time (in that time range) where the
probability is that once heated water is colder than the ice.

On Jul 14, 5:42?am, pau...@saaf.se (Paul Schlyter) wrote:
> In article <1184355936.720567.167...@o11g2000prd.googlegroups .com>,
>
> Radium <gluceg...@gmail.com> wrote:
> > 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?
>
> SInce the cooloff is pretty much exponential, it will take forever and
> the rediated energy will never drop to exactly zero. SO you should
> rephrase your question as:
>
> # 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
> # any significant anounts of heat or light [or other energies] than
> # the surrounding space?
>
> That time span will depend a lot on your precise definition of
> "significant". But it will probably take hundreds of billion years,
> or more.
>
> Let me give you one concrete example: suppose the outside temperature
> is exactly freezing, i.e. 0 deg C. You boil a pot of water, then
> bring it outside. How long time will it take until the pot has
> cooled down so there's no temperature difference between the pot
> of water and the surroundings?
>
> 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!
>
> Of course a temperature difference of 1E-6 degrees or smaller is
> indistinguishable from zero - we call such a difference insignificant.
>
> But where do you draw the line between "significant" and
> "insignificant" here? In the example above, do you consider the
> temperature of the pot of water to be "the same" as the surroundings
> when the temperature difference drops below one degree? If so, it
> will happen after two hours. Or do you require a temperature
> difference of less than 0.01 degrees to consider the temperatures "the
> same"? If so, the cooldown will require four hours.
>
> The situation is similar with a white dwarf: no internal fusion gives
> any energy anymore, so the white dwarf just cools down. OK, there's
> one internal energy source remaining: gravitational contraction: the
> white dwarf can contract somewhat under its own gravitation, and that
> will release some energy, keeping it warmer for some time(*). But
> still the white dwarf cools off more or less exponentially. Now,
> since the white dwarfs are faint stars, they don't radiate that much
> energy out into space, and that's one major reason they can "live" for
> so long.
>
> (*) Before astronomer's realized that the Sun's energy source was nuclear
> fusion, other sources of energy were suggested. If the Sun had been
> a huge coal fire, it would be able to shine only for a few centuries,
> maybe a millennium. A more efficient energy source was gravitational
> contraction, which would be able to keep the Sun hot for approximately
> a million years. Back then, geologists suggesting that the Earth is
> some 5 billion years old had an obvious difficulty: what energy source
> could have kept the Sun shining for those five billion years? The
> answer is of course nuclear fusion - but it wasn't until well into the
> 1900's that astronomers realized this.
>
> --
> ----------------------------------------------------------------
> Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
> e-mail: pausch at stockholm dot bostream dot se
> WWW: http://stjarnhimlen.se/

"Chris L Peterson" <clp@alumni.caltech.edu> wrote in message
news:rplh93973ll761k6cgsnpufj37n1qvtnck@4ax.com...
> On Sat, 14 Jul 2007 09:42:19 GMT, pausch@saaf.se (Paul Schlyter) wrote:
>
>>That would take forever too!!!
>
> That's true. I meant until the level of visible photons drops below
> detectability (which is, of course, a moving target). As you say, all
> that can be done is to set a threshold, or a specific target
> temperature.

I think the OP asked about 70F with the idea of having
some humans around. His question is really whether there
could be habitable planets around at a time when the
galaxies were evaporating rather than how long it would
take for a white dwarf to cool to 290K.

One can imagine a time when gathering hydrogen to keep
their brown dwarf running was a civilisation's main
occupation, but I guess that's another story.

George

Paul Schlyter wrote: (snip)

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

Quoting Style in Newsgroup Postings
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/

On 13 juuli, 22:45, Radium <gluceg...@gmail.com> 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...

On Mon, 16 Jul 2007 08:39:07 -0700, Crown-Horned Snorkack
<chornedsnorkack@hush.ai> 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

	#1
Radium	How long will the sun remain a white dwarf? 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

	#2
Sam Wormley	Re: How long will the sun remain a white dwarf? Radium wrote: > > 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? > The Cooling of CO White Dwarfs: Influence of the Internal Chemical Distribution http://www.journals.uchicago.edu/ApJ...903/34903.html

	#3
Chris L Peterson	Re: How long will the sun remain a white dwarf? On Fri, 13 Jul 2007 19:45:36 -0000, Radium <glucegen1@gmail.com> 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? That would take forever. But a few tens of billions of years should be long enough that the temperature drops low enough that no photons in the visible range are produced, which is generally what defines a black dwarf. _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com

	#7
William Hamblen	Re: How long will the sun remain a white dwarf? On Fri, 13 Jul 2007 19:45:36 -0000, Radium <glucegen1@gmail.com> wrote: >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? It takes a solar type star about 100 billion years, which is more than the presently estimated age of the universe. Bud -- The night is just the shadow of the Earth.

	#8
Paul Schlyter	Re: How long will the sun remain a white dwarf? In article <1184355936.720567.167930@o11g2000prd.googlegroups .com>, Radium <glucegen1@gmail.com> wrote: > 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? SInce the cooloff is pretty much exponential, it will take forever and the rediated energy will never drop to exactly zero. SO you should rephrase your question as: # 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 # any significant anounts of heat or light [or other energies] than # the surrounding space? That time span will depend a lot on your precise definition of "significant". But it will probably take hundreds of billion years, or more. Let me give you one concrete example: suppose the outside temperature is exactly freezing, i.e. 0 deg C. You boil a pot of water, then bring it outside. How long time will it take until the pot has cooled down so there's no temperature difference between the pot of water and the surroundings? 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! Of course a temperature difference of 1E-6 degrees or smaller is indistinguishable from zero - we call such a difference insignificant. But where do you draw the line between "significant" and "insignificant" here? In the example above, do you consider the temperature of the pot of water to be "the same" as the surroundings when the temperature difference drops below one degree? If so, it will happen after two hours. Or do you require a temperature difference of less than 0.01 degrees to consider the temperatures "the same"? If so, the cooldown will require four hours. The situation is similar with a white dwarf: no internal fusion gives any energy anymore, so the white dwarf just cools down. OK, there's one internal energy source remaining: gravitational contraction: the white dwarf can contract somewhat under its own gravitation, and that will release some energy, keeping it warmer for some time(). But still the white dwarf cools off more or less exponentially. Now, since the white dwarfs are faint stars, they don't radiate that much energy out into space, and that's one major reason they can "live" for so long. () Before astronomer's realized that the Sun's energy source was nuclear fusion, other sources of energy were suggested. If the Sun had been a huge coal fire, it would be able to shine only for a few centuries, maybe a millennium. A more efficient energy source was gravitational contraction, which would be able to keep the Sun hot for approximately a million years. Back then, geologists suggesting that the Earth is some 5 billion years old had an obvious difficulty: what energy source could have kept the Sun shining for those five billion years? The answer is of course nuclear fusion - but it wasn't until well into the 1900's that astronomers realized this. -- ---------------------------------------------------------------- Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN e-mail: pausch at stockholm dot bostream dot se WWW: http://stjarnhimlen.se/

	#11
Havriliak@aol.com	Re: How long will the sun remain a white dwarf? Don'tforget about fluctuation theory, sometimes known as Statistical Mechanics. You will et a time (in that time range) where the probability is that once heated water is colder than the ice. On Jul 14, 5:42?am, pau...@saaf.se (Paul Schlyter) wrote: > In article <1184355936.720567.167...@o11g2000prd.googlegroups .com>, > > Radium <gluceg...@gmail.com> wrote: > > 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? > > SInce the cooloff is pretty much exponential, it will take forever and > the rediated energy will never drop to exactly zero. SO you should > rephrase your question as: > > # 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 > # any significant anounts of heat or light [or other energies] than > # the surrounding space? > > That time span will depend a lot on your precise definition of > "significant". But it will probably take hundreds of billion years, > or more. > > Let me give you one concrete example: suppose the outside temperature > is exactly freezing, i.e. 0 deg C. You boil a pot of water, then > bring it outside. How long time will it take until the pot has > cooled down so there's no temperature difference between the pot > of water and the surroundings? > > 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! > > Of course a temperature difference of 1E-6 degrees or smaller is > indistinguishable from zero - we call such a difference insignificant. > > But where do you draw the line between "significant" and > "insignificant" here? In the example above, do you consider the > temperature of the pot of water to be "the same" as the surroundings > when the temperature difference drops below one degree? If so, it > will happen after two hours. Or do you require a temperature > difference of less than 0.01 degrees to consider the temperatures "the > same"? If so, the cooldown will require four hours. > > The situation is similar with a white dwarf: no internal fusion gives > any energy anymore, so the white dwarf just cools down. OK, there's > one internal energy source remaining: gravitational contraction: the > white dwarf can contract somewhat under its own gravitation, and that > will release some energy, keeping it warmer for some time(). But > still the white dwarf cools off more or less exponentially. Now, > since the white dwarfs are faint stars, they don't radiate that much > energy out into space, and that's one major reason they can "live" for > so long. > > () Before astronomer's realized that the Sun's energy source was nuclear > fusion, other sources of energy were suggested. If the Sun had been > a huge coal fire, it would be able to shine only for a few centuries, > maybe a millennium. A more efficient energy source was gravitational > contraction, which would be able to keep the Sun hot for approximately > a million years. Back then, geologists suggesting that the Earth is > some 5 billion years old had an obvious difficulty: what energy source > could have kept the Sun shining for those five billion years? The > answer is of course nuclear fusion - but it wasn't until well into the > 1900's that astronomers realized this. > > -- > ---------------------------------------------------------------- > Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN > e-mail: pausch at stockholm dot bostream dot se > WWW: http://stjarnhimlen.se/

	#12
George Dishman	Re: How long will the sun remain a white dwarf? "Chris L Peterson" <clp@alumni.caltech.edu> wrote in message news:rplh93973ll761k6cgsnpufj37n1qvtnck@4ax.com... > On Sat, 14 Jul 2007 09:42:19 GMT, pausch@saaf.se (Paul Schlyter) wrote: > >>That would take forever too!!! > > That's true. I meant until the level of visible photons drops below > detectability (which is, of course, a moving target). As you say, all > that can be done is to set a threshold, or a specific target > temperature. I think the OP asked about 70F with the idea of having some humans around. His question is really whether there could be habitable planets around at a time when the galaxies were evaporating rather than how long it would take for a white dwarf to cool to 290K. One can imagine a time when gathering hydrogen to keep their brown dwarf running was a civilisation's main occupation, but I guess that's another story. George

	#13
invalid@example.com	Re: 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:: Quoting Style in Newsgroup Postings 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/

	#14
Crown-Horned Snorkack	Re: How long will the sun remain a white dwarf? On 13 juuli, 22:45, Radium <gluceg...@gmail.com> 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...