Definition of the sun's "death"?

Hi:

I just don't understand why the expansion of the sun into a red giant
would be classified as the sun's 'death'. As a red giant, the sun will
very much be alive as it is today. It will burn helium instead of the
hydrogen it burns today.

My definition of the "death of the sun", is when the sun ceases its
nuclear fusion. Fusion is what gives the sun its life.

Best,

Radium

Radium wrote:
> Hi:
>
> I just don't understand why the expansion of the sun into a red giant
> would be classified as the sun's 'death'. As a red giant, the sun will
> very much be alive as it is today. It will burn helium instead of the
> hydrogen it burns today.
>
> My definition of the "death of the sun", is when the sun ceases its
> nuclear fusion. Fusion is what gives the sun its life.
>
>
> Best,
>
> Radium
>

Stars spend the majority of their "lives" on the main sequence, i.e.,
fusing hydrogen into helium. and the secondary, tertiary, etc. fusion
processes are short lived by comparison.

Star are born and stars die... just like us. The big massive stars have
but short lives, a few millions of years. Stars like our sun last for a
good 10 billions of years, and the little red stars like Barnard's Star
might last for 100 billion years. How long stars live, is determined by
their mass (which must be at least 80 Jupiter masses to sustain
thermonuclear fusion of hydrogen).

There are four (4) fates for the end of stars depending on their masses
and the masses of their cores:

Red/Brown Dwarfs - less than 0.6 Ms <== Main Sequence 0.076-0.8 Ms
Stars less than about 0.6 solar masses, when nuclear fuel is used up,
gravitational collapse shrinks the star, but no more than the gas
temperature-pressure-volume laws of classical physics allow. We have
not found any white dwarf less massive than 0.6 solar masses. Part of
the answer is that the universe may not be old enough for lower mass
stars to have evolved off the main sequence.

White Dwarfs - 0.6 and 1.44 Ms <== Main Sequence 0.8-8 Ms
Stars with core masses between 0.6 and 1.44 solar masses are
destined to become white dwarfs. White dwarfs are degenerate matter.
Further collapse is halted by electron degeneracy pressure. See pages
456-459 in your textbook. The vast majority of stars are in this mass
range and are destined to become white dwarfs

Neutron Stars - 1.44 and 2.9 Ms <== Main Sequence 8-30 Ms
Core masses between 1.44 and 2.9 solar masses overcome electron
degeneracy pressure and collapse to form neutron stars, a star that is
essentially one gigantic nucleus. Further collapse is halted by neutron
degeneracy pressure.

Black Holes - 3 or more Ms <== Main Sequence > 30 Ms
But for cores with mass of 3 or more solar masses, neutron
degeneracy pressure does not stop the collapse and the star becomes a
black hole with zero physical size, but with all the mass. Gravity
really wins!

In each case, gravity eventually wins, but, to what extent is
determined by the mass and the relative pressures of the quantum
mechanical forces, electron and neutron degeneracy pressure. Your book
has an excellent diagram on page 459 relating the original star mass to
that of the final core mass (core mass being the mass of whats left of
the star at the end of its evolutionary processes).

On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote:

> I just don't understand why the expansion of the sun
> into a red giant would be classified as the sun's 'death'.
> ...
> My definition of the "death of the sun", is when the sun
> ceases its nuclear fusion.

I agree; it's sloppy terminology. A better term might be
death throes. But even that I'd save for the truly
terminal phase when the Sun creates a planetary
nebula. The red-giant phase would better be called
old age.

Of course, stars continue to shine quite nicely even
after nuclear fusion has stopped. I would call a
white dwarf moribund rather than dead.

Dear tony_flanders:

<tony_flanders@yahoo.com> wrote in message
news:1184331265.571374.137330@n60g2000hse.googlegr oups.com...
> On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote:
>
>> I just don't understand why the expansion of the sun
>> into a red giant would be classified as the sun's 'death'.
>> ...
>> My definition of the "death of the sun", is when the sun
>> ceases its nuclear fusion.
>
> I agree; it's sloppy terminology. A better term might be
> death throes. But even that I'd save for the truly
> terminal phase when the Sun creates a planetary
> nebula. The red-giant phase would better be called
> old age.

How about "menopausal"? ;>)

> Of course, stars continue to shine quite nicely even
> after nuclear fusion has stopped. I would call a
> white dwarf moribund rather than dead.

David A. Smith

On Jul 13, 6:09 am, "N:dlzc D:aol T:com $dlzc$" <d...@aol.com>
wrote:
> Dear tony_flanders:
>
> <tony_fland...@yahoo.com> wrote in message
>
> news:1184331265.571374.137330@n60g2000hse.googlegr oups.com...
>
> > On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote:
>
> >> I just don't understand why the expansion of the sun
> >> into a red giant would be classified as the sun's 'death'.
> >> ...
> >> My definition of the "death of the sun", is when the sun
> >> ceases its nuclear fusion.
>
> > I agree; it's sloppy terminology. A better term might be
> > death throes. But even that I'd save for the truly
> > terminal phase when the Sun creates a planetary
> > nebula. The red-giant phase would better be called
> > old age.
>
> How about "menopausal"? ;>)
>
> > Of course, stars continue to shine quite nicely even
> > after nuclear fusion has stopped. I would call a
> > white dwarf moribund rather than dead.
>
> David A. Smith

Why do we insist on using such anthropomorphic terminology anyway?
Objects in space don't get born, live, and then die, they transition
from one kind of object into another. When we apply the terms of
carbon based life forms to inanimate objects, we are being completely
arbitrary. Otherwise, when a super massive star collapses, why not
say, "A black hole is born!"?

Double-A

On Fri, 13 Jul 2007 07:34:50 -0700, Double-A <double-aa@hush.ai> wrote:

>
>Why do we insist on using such anthropomorphic terminology anyway?
>Objects in space don't get born, live, and then die, they transition
>from one kind of object into another. When we apply the terms of
>carbon based life forms to inanimate objects, we are being completely
>arbitrary. Otherwise, when a super massive star collapses, why not
>say, "A black hole is born!"?

I've heard that last said many times.

It is in our nature to anthropomorphize our environment. And in fact, it
is perfectly reasonable (even from a scientific standpoint) to speak of
the birth, life, and death of a star. Stars don't exist forever in
either direction, even if their material does. I could argue that you
were never born, but just transformed from a different kind of object
<g>.

_________________________________________________

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

Radium wrote:
> Hi:
>
> I just don't understand why the expansion of the sun into a red giant
> would be classified as the sun's 'death'. As a red giant, the sun will
> very much be alive as it is today. It will burn helium instead of the
> hydrogen it burns today.

I like "senescence". Big word, sounds good ;-)

> My definition of the "death of the sun", is when the sun ceases its
> nuclear fusion. Fusion is what gives the sun its life.

Qualified in that "life of a star" sense, as opposed to biological life,
I agree.

Shawn

Radium wrote:
> Hi:
>
> I just don't understand why the expansion of the sun into a red giant
> would be classified as the sun's 'death'. As a red giant, the sun will
> very much be alive as it is today. It will burn helium instead of the
> hydrogen it burns today.
>
> My definition of the "death of the sun", is when the sun ceases its
> nuclear fusion. Fusion is what gives the sun its life.
>

Fusion (after the radiation pressure of gravitational collapse) keeps
the star inflated against gravity... eventually gravity wins!

On Fri, 13 Jul 2007 16:55:54 GMT, Sam Wormley <swormley1@mchsi.com>
wrote:

> Fusion (after the radiation pressure of gravitational collapse) keeps
> the star inflated against gravity... eventually gravity wins!

A fact that applies to people as well <g>.

_________________________________________________

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

On Jul 13, 7:43 am, Chris L Peterson <c...@alumni.caltech.edu> wrote:
> On Fri, 13 Jul 2007 07:34:50 -0700, Double-A <double...@hush.ai> wrote:
>
> >Why do we insist on using such anthropomorphic terminology anyway?
> >Objects in space don't get born, live, and then die, they transition
> >from one kind of object into another. When we apply the terms of
> >carbon based life forms to inanimate objects, we are being completely
> >arbitrary. Otherwise, when a super massive star collapses, why not
> >say, "A black hole is born!"?
>
> I've heard that last said many times.
>
> It is in our nature to anthropomorphize our environment. And in fact, it
> is perfectly reasonable (even from a scientific standpoint) to speak of
> the birth, life, and death of a star. Stars don't exist forever in
> either direction, even if their material does. I could argue that you
> were never born, but just transformed from a different kind of object
> <g>.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatoryhttp://www.cloudbait.com

And so I was, O enlightened one.

Double-A

"Double-A" <double-aa@hush.ai> wrote in message
news:1184337290.253768.63600@i13g2000prf.googlegro ups.com...
: On Jul 13, 6:09 am, "N:dlzc D:aol T:com $dlzc$" <d...@aol.com>
: wrote:
: > Dear tony_flanders:
: >
: > <tony_fland...@yahoo.com> wrote in message
: >
: > news:1184331265.571374.137330@n60g2000hse.googlegr oups.com...
: >
: > > On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote:
: >
: > >> I just don't understand why the expansion of the sun
: > >> into a red giant would be classified as the sun's 'death'.
: > >> ...
: > >> My definition of the "death of the sun", is when the sun
: > >> ceases its nuclear fusion.
: >
: > > I agree; it's sloppy terminology. A better term might be
: > > death throes. But even that I'd save for the truly
: > > terminal phase when the Sun creates a planetary
: > > nebula. The red-giant phase would better be called
: > > old age.
: >
: > How about "menopausal"? ;>)
: >
: > > Of course, stars continue to shine quite nicely even
: > > after nuclear fusion has stopped. I would call a
: > > white dwarf moribund rather than dead.
: >
: > David A. Smith
:
: Why do we insist on using such anthropomorphic terminology anyway?
: Objects in space don't get born, live, and then die, they transition
: from one kind of object into another. When we apply the terms of
: carbon based life forms to inanimate objects, we are being completely
: arbitrary. Otherwise, when a super massive star collapses, why not
: say, "A black hole is born!"?

Black hole... a snake swallowing its own tail.

Possibly a neutron body... the nuclei, protons and electrons
compressed under gravity at the core; but at the surface, cold
evaporation to leave huge clouds of hydrogen light years across
and talking billions of years to form,

http://antwrp.gsfc.nasa.gov/apod/ap070106.html

which slowly absorb radiation from other stars before condensing
again to complete the cycle, the conclusion being a universe that always
was and always will be.

The core? Planets such as the Earth would fit the description
rather well with its abundance of heavy elements.

"Beginning" and "ending" are also anthropomorphisms, yet life itself
is cyclic, energy driven, so why should not the universe be so as well?

Big Bangs and black holes are rather silly theories, that's all.
If there were a big bang there'd be a detectable point from which
everything radiated, yet even the CMBR is homogeneous.
http://antwrp.gsfc.nasa.gov/apod/ap061007.html

And then there is this:
http://antwrp.gsfc.nasa.gov/apod/ap061008.html

The evidence for either wild conjecture simply isn't there, we
must examine the universe from ALL the data before we can
call ourselves scientists.

In article <LADli.26938$Fc.8903@attbi_s21>,
Sam Wormley <swormley1@mchsi.com> wrote:

<snip>

> Your book has an excellent diagram on page 459 relating the original
> star mass to that of the final core mass (core mass being the mass of
> whats left of the star at the end of its evolutionary processes).

What book is that? I assume your posting was taken from class notes --
what course?

--
Odysseus

In article <odysseus1479-at-3033AE.03080814072007@news.telus.net>, Odysseus <odysseus1479-at@yahoo-dot.ca> wrote:
>In article <LADli.26938$Fc.8903@attbi_s21>,
> Sam Wormley <swormley1@mchsi.com> wrote:
>
><snip>
>
>> Your book has an excellent diagram on page 459 relating the original
>> star mass to that of the final core mass (core mass being the mass of
>> whats left of the star at the end of its evolutionary processes).
>
>What book is that? I assume your posting was taken from class notes --
>what course?

Glad I wasn't the only one wondering about this. I looked at the thread
and other possibly related threads and couldn't work out what the
reference to "your book" was all about. I'd like to find out as well.

In article <odysseus1479-at-3033AE.03080814072007@news.telus.net>, Odysseus <odysseus1479-at@yahoo-dot.ca> wrote:
>In article <LADli.26938$Fc.8903@attbi_s21>,
> Sam Wormley <swormley1@mchsi.com> wrote:
>
><snip>
>
>> Your book has an excellent diagram on page 459 relating the original
>> star mass to that of the final core mass (core mass being the mass of
>> whats left of the star at the end of its evolutionary processes).
>
>What book is that? I assume your posting was taken from class notes --
>what course?

Google can be so useful sometimes. It's a direct quote from:

http://edu-observatory.org/mcc/homew...19/homework.ch.
18-19.html

Odysseus wrote:
> In article <LADli.26938$Fc.8903@attbi_s21>,
> Sam Wormley <swormley1@mchsi.com> wrote:
>
> <snip>
>
>> Your book has an excellent diagram on page 459 relating the original
>> star mass to that of the final core mass (core mass being the mass of
>> whats left of the star at the end of its evolutionary processes).
>
> What book is that? I assume your posting was taken from class notes --
> what course?
>

I've been teaching from "Astronomy: Journey To The Cosmic Frontier", 4th ed
by John D. Fix ISBN: 007299181x
http://www.mhhe.com/fix/

Syllabus
http://edu-observatory.org/mcc/syllabus

Sam Wormley wrote:
> Radium wrote:
>> Hi:
>>
>> I just don't understand why the expansion of the sun into a red giant
>> would be classified as the sun's 'death'. As a red giant, the sun will
>> very much be alive as it is today. It will burn helium instead of the
>> hydrogen it burns today.
>>
>> My definition of the "death of the sun", is when the sun ceases its
>> nuclear fusion. Fusion is what gives the sun its life.
>>
>>
>> Best,
>>
>> Radium
>>
>
> Stars spend the majority of their "lives" on the main sequence, i.e.,
> fusing hydrogen into helium. and the secondary, tertiary, etc. fusion
> processes are short lived by comparison.
>
> Star are born and stars die... just like us. The big massive stars have
> but short lives, a few millions of years. Stars like our sun last for a
> good 10 billions of years, and the little red stars like Barnard's Star
> might last for 100 billion years. How long stars live, is determined by
> their mass (which must be at least 80 Jupiter masses to sustain
> thermonuclear fusion of hydrogen).
>
> There are four (4) fates for the end of stars depending on their masses
> and the masses of their cores:
>
> Red/Brown Dwarfs - less than 0.6 Ms <== Main Sequence 0.076-0.8 Ms
> Stars less than about 0.6 solar masses, when nuclear fuel is used up,
> gravitational collapse shrinks the star, but no more than the gas
> temperature-pressure-volume laws of classical physics allow. We have
> not found any white dwarf less massive than 0.6 solar masses. Part of
> the answer is that the universe may not be old enough for lower mass
> stars to have evolved off the main sequence.
>
> White Dwarfs - 0.6 and 1.44 Ms <== Main Sequence 0.8-8 Ms
> Stars with core masses between 0.6 and 1.44 solar masses are
> destined to become white dwarfs. White dwarfs are degenerate matter.
> Further collapse is halted by electron degeneracy pressure. See pages
> 456-459 in your textbook. The vast majority of stars are in this mass
> range and are destined to become white dwarfs
>
> Neutron Stars - 1.44 and 2.9 Ms <== Main Sequence 8-30 Ms
> Core masses between 1.44 and 2.9 solar masses overcome electron
> degeneracy pressure and collapse to form neutron stars, a star that is
> essentially one gigantic nucleus. Further collapse is halted by neutron
> degeneracy pressure.
>
> Black Holes - 3 or more Ms <== Main Sequence > 30 Ms
> But for cores with mass of 3 or more solar masses, neutron
> degeneracy pressure does not stop the collapse and the star becomes a
> black hole with zero physical size, but with all the mass. Gravity
> really wins!
>
> In each case, gravity eventually wins, but, to what extent is
> determined by the mass and the relative pressures of the quantum
> mechanical forces, electron and neutron degeneracy pressure. Your book
> has an excellent diagram on page 459 relating the original star mass to
> that of the final core mass (core mass being the mass of whats left of
> the star at the end of its evolutionary processes).

Something I'd like to know:

Just what will be left of a star (that won't explode into a neutron star
or black hole) some 20 billion years from now. A cold, spinning sphere
of iron that you could walk on?

All stellar 'histories' that I have read (maybe I should say
understood), don't seem to elaborate on this.

As for the neutron star: Has there been any speculation as to how this
would appear if you could orbit one from a safe distance?

--
Stupot http://insignity.blogspot.com

Stuart Chapman wrote:

>
> Something I'd like to know:
>
> Just what will be left of a star (that won't explode into a neutron star
> or black hole) some 20 billion years from now. A cold, spinning sphere
> of iron that you could walk on?
>
> All stellar 'histories' that I have read (maybe I should say
> understood), don't seem to elaborate on this.
>
> As for the neutron star: Has there been any speculation as to how this
> would appear if you could orbit one from a safe distance?
>

When there is no further energy source to hold up a star the star will
become degenerate with total mass greater than about 0.6 solar masses.
And of course there is a limit--the Chandrasekhar limit of 1.44 solar
masses. The remnant will most likely have a gas surface for a very long
time, however trillions of years into the future it should "freeze"
solid. As for walking on it... the gravitation would be enormous.

Stuart Chapman nous a donc écrit :

> Something I'd like to know:
>
> Just what will be left of a star (that won't explode into a neutron
> star or black hole) some 20 billion years from now. A cold, spinning
> sphere of iron that you could walk on?

Not iron. Degenerate electronic matter is the constituent of a white dwarf.
Don't ask me the aspect of this matter

You could obviously walk on it, if you are not crushed by gravitation.
And in 20 billion years, this sphere of matter will surely be as cold as the
rest of the universe.
>
> All stellar 'histories' that I have read (maybe I should say
> understood), don't seem to elaborate on this.
>
> As for the neutron star: Has there been any speculation as to how this
> would appear if you could orbit one from a safe distance?

You could refer to this page
http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html where you will find some
animation films about travelling to a neutron star.
The aspect of a neutron star must be a (quite) perfect sphere of iron, which
forms the crust of the star.

--
Norbert. (no X for the answer)
======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

On Mon, 16 Jul 2007 16:06:14 +0200, "Norbert"
<Xnorbert.rumiano@numericable.frX> wrote:

>Not iron. Degenerate electronic matter is the constituent of a white dwarf.
>Don't ask me the aspect of this matter

>You could obviously walk on it, if you are not crushed by gravitation.
>And in 20 billion years, this sphere of matter will surely be as cold as the
>rest of the universe.

I think that in just 20 billion years, you'd still get toasted pretty
well walking on the surface of a neutron star. It would still be a few
thousand degrees. Better give it at least a few hundred billion years if
you want it cool enough to walk on.

_________________________________________________

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

Chris L Peterson nous a donc écrit :

> On Mon, 16 Jul 2007 16:06:14 +0200, "Norbert"
> <Xnorbert.rumiano@numericable.frX> wrote:
>
>> Not iron. Degenerate electronic matter is the constituent of a white
>> dwarf. Don't ask me the aspect of this matter

>> You could obviously walk on it, if you are not crushed by
>> gravitation.
>> And in 20 billion years, this sphere of matter will surely be as
>> cold as the rest of the universe.
>
> I think that in just 20 billion years, you'd still get toasted pretty
> well walking on the surface of a neutron star. It would still be a few
> thousand degrees. Better give it at least a few hundred billion years
> if you want it cool enough to walk on.
>
I was talking about white dwarf. And from
http://www.journals.uchicago.edu/ApJ...864961312Guest
it seems that about 10 billion years will be enough.

Of course, for a neutron star, it will take a much much longer time

--
Norbert. (no X for the answer)
======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

On Mon, 16 Jul 2007 17:11:52 +0200, "Norbert"
<Xnorbert.rumiano@numericable.frX> wrote:

>I was talking about white dwarf. And from
>http://www.journals.uchicago.edu/ApJ...864961312Guest
>it seems that about 10 billion years will be enough.

Sorry, I was thinking white dwarf even while typing neutron star. And
from my reading of the referenced paper, a typical white dwarf
temperature will be about 15,000 K after 10 billion years... a little
warmer than I'd care to walk on! That temperature is also in line with
what you get modeling the luminosity function as a simple exponential
(which was the source of my time estimates elsewhere in this
discussion).

_________________________________________________

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

Chris L Peterson nous a donc écrit :

> On Mon, 16 Jul 2007 17:11:52 +0200, "Norbert"
> <Xnorbert.rumiano@numericable.frX> wrote:
>
>> I was talking about white dwarf. And from
>> http://www.journals.uchicago.edu/ApJ...864961312Guest
>> it seems that about 10 billion years will be enough.
>
> Sorry, I was thinking white dwarf even while typing neutron star. And
> from my reading of the referenced paper, a typical white dwarf
> temperature will be about 15,000 K after 10 billion years... a little
> warmer than I'd care to walk on! That temperature is also in line with
> what you get modeling the luminosity function as a simple exponential
> (which was the source of my time estimates elsewhere in this
> discussion).
>
Chris, you're right. My first reading of this article was a bit too fast.
I agree : I won't put my feet on such a star

--
Norbert. (no X for the answer)
======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

On Jul 16, 3:06 pm, "Norbert" <Xnorbert.rumi...@numericable.frX>
wrote:
> Stuart Chapman nous a donc écrit :
>
> > Something I'd like to know:
>
> > Just what will be left of a star (that won't explode into a neutron
> > star or black hole) some 20 billion years from now. A cold, spinning
> > sphere of iron that you could walk on?
>
> Not iron. Degenerate electronic matter is the constituent of a white dwarf.
> Don't ask me the aspect of this matter

Mostly at the surface chemically it will be carbon and oxygen when it
cools down enough to recombine from a plasma. And crystallisation is
believed to play a part in the cooling of white dwarfs when the
surface temperature falls below about 6000K (typically 5x10^9 years
after formation).

> You could obviously walk on it, if you are not crushed by gravitation.
> And in 20 billion years, this sphere of matter will surely be as cold as the
> rest of the universe.

I think I would prefer to wait about 10^12 years for it to cool. By
then if current theories are correct it will be a roughly Earth sized
diamond with an iron core and very unpleasantly strong surface
gravity.

Various ZZ Cetae type white dwarf type stars are being studied to try
and understand their cooling processes.
eg http://www.aas.org/publications/baas...aas203/181.htm
more popular version
http://news.bbc.co.uk/1/hi/sci/tech/3492919.stm

Regards,
Martin Brown

	#1
Radium	Definition of the sun's "death"? Hi: I just don't understand why the expansion of the sun into a red giant would be classified as the sun's 'death'. As a red giant, the sun will very much be alive as it is today. It will burn helium instead of the hydrogen it burns today. My definition of the "death of the sun", is when the sun ceases its nuclear fusion. Fusion is what gives the sun its life. Best, Radium

	#2
Sam Wormley	Re: Definition of the sun's "death"? Radium wrote: > Hi: > > I just don't understand why the expansion of the sun into a red giant > would be classified as the sun's 'death'. As a red giant, the sun will > very much be alive as it is today. It will burn helium instead of the > hydrogen it burns today. > > My definition of the "death of the sun", is when the sun ceases its > nuclear fusion. Fusion is what gives the sun its life. > > > Best, > > Radium > Stars spend the majority of their "lives" on the main sequence, i.e., fusing hydrogen into helium. and the secondary, tertiary, etc. fusion processes are short lived by comparison. Star are born and stars die... just like us. The big massive stars have but short lives, a few millions of years. Stars like our sun last for a good 10 billions of years, and the little red stars like Barnard's Star might last for 100 billion years. How long stars live, is determined by their mass (which must be at least 80 Jupiter masses to sustain thermonuclear fusion of hydrogen). There are four (4) fates for the end of stars depending on their masses and the masses of their cores: Red/Brown Dwarfs - less than 0.6 Ms <== Main Sequence 0.076-0.8 Ms Stars less than about 0.6 solar masses, when nuclear fuel is used up, gravitational collapse shrinks the star, but no more than the gas temperature-pressure-volume laws of classical physics allow. We have not found any white dwarf less massive than 0.6 solar masses. Part of the answer is that the universe may not be old enough for lower mass stars to have evolved off the main sequence. White Dwarfs - 0.6 and 1.44 Ms <== Main Sequence 0.8-8 Ms Stars with core masses between 0.6 and 1.44 solar masses are destined to become white dwarfs. White dwarfs are degenerate matter. Further collapse is halted by electron degeneracy pressure. See pages 456-459 in your textbook. The vast majority of stars are in this mass range and are destined to become white dwarfs Neutron Stars - 1.44 and 2.9 Ms <== Main Sequence 8-30 Ms Core masses between 1.44 and 2.9 solar masses overcome electron degeneracy pressure and collapse to form neutron stars, a star that is essentially one gigantic nucleus. Further collapse is halted by neutron degeneracy pressure. Black Holes - 3 or more Ms <== Main Sequence > 30 Ms But for cores with mass of 3 or more solar masses, neutron degeneracy pressure does not stop the collapse and the star becomes a black hole with zero physical size, but with all the mass. Gravity really wins! In each case, gravity eventually wins, but, to what extent is determined by the mass and the relative pressures of the quantum mechanical forces, electron and neutron degeneracy pressure. Your book has an excellent diagram on page 459 relating the original star mass to that of the final core mass (core mass being the mass of whats left of the star at the end of its evolutionary processes).

	#3
tony_flanders@yahoo.com	Re: Definition of the sun's "death"? On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote: > I just don't understand why the expansion of the sun > into a red giant would be classified as the sun's 'death'. > ... > My definition of the "death of the sun", is when the sun > ceases its nuclear fusion. I agree; it's sloppy terminology. A better term might be death throes. But even that I'd save for the truly terminal phase when the Sun creates a planetary nebula. The red-giant phase would better be called old age. Of course, stars continue to shine quite nicely even after nuclear fusion has stopped. I would call a white dwarf moribund rather than dead.

	#4
N:dlzc D:aol T:com \(dlzc\)	Re: Definition of the sun's "death"? Dear tony_flanders: <tony_flanders@yahoo.com> wrote in message news:1184331265.571374.137330@n60g2000hse.googlegr oups.com... > On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote: > >> I just don't understand why the expansion of the sun >> into a red giant would be classified as the sun's 'death'. >> ... >> My definition of the "death of the sun", is when the sun >> ceases its nuclear fusion. > > I agree; it's sloppy terminology. A better term might be > death throes. But even that I'd save for the truly > terminal phase when the Sun creates a planetary > nebula. The red-giant phase would better be called > old age. How about "menopausal"? ;>) > Of course, stars continue to shine quite nicely even > after nuclear fusion has stopped. I would call a > white dwarf moribund rather than dead. David A. Smith

	#5
Double-A	Re: Definition of the sun's "death"? On Jul 13, 6:09 am, "N:dlzc D:aol T:com \(dlzc\)" <d...@aol.com> wrote: > Dear tony_flanders: > > <tony_fland...@yahoo.com> wrote in message > > news:1184331265.571374.137330@n60g2000hse.googlegr oups.com... > > > On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote: > > >> I just don't understand why the expansion of the sun > >> into a red giant would be classified as the sun's 'death'. > >> ... > >> My definition of the "death of the sun", is when the sun > >> ceases its nuclear fusion. > > > I agree; it's sloppy terminology. A better term might be > > death throes. But even that I'd save for the truly > > terminal phase when the Sun creates a planetary > > nebula. The red-giant phase would better be called > > old age. > > How about "menopausal"? ;>) > > > Of course, stars continue to shine quite nicely even > > after nuclear fusion has stopped. I would call a > > white dwarf moribund rather than dead. > > David A. Smith Why do we insist on using such anthropomorphic terminology anyway? Objects in space don't get born, live, and then die, they transition from one kind of object into another. When we apply the terms of carbon based life forms to inanimate objects, we are being completely arbitrary. Otherwise, when a super massive star collapses, why not say, "A black hole is born!"? Double-A

	#6
Chris L Peterson	Re: Definition of the sun's "death"? On Fri, 13 Jul 2007 07:34:50 -0700, Double-A <double-aa@hush.ai> wrote: > >Why do we insist on using such anthropomorphic terminology anyway? >Objects in space don't get born, live, and then die, they transition >from one kind of object into another. When we apply the terms of >carbon based life forms to inanimate objects, we are being completely >arbitrary. Otherwise, when a super massive star collapses, why not >say, "A black hole is born!"? I've heard that last said many times. It is in our nature to anthropomorphize our environment. And in fact, it is perfectly reasonable (even from a scientific standpoint) to speak of the birth, life, and death of a star. Stars don't exist forever in either direction, even if their material does. I could argue that you were never born, but just transformed from a different kind of object <g>. _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com

	#7
Shawn	Re: Definition of the sun's "death"? Radium wrote: > Hi: > > I just don't understand why the expansion of the sun into a red giant > would be classified as the sun's 'death'. As a red giant, the sun will > very much be alive as it is today. It will burn helium instead of the > hydrogen it burns today. I like "senescence". Big word, sounds good ;-) > My definition of the "death of the sun", is when the sun ceases its > nuclear fusion. Fusion is what gives the sun its life. Qualified in that "life of a star" sense, as opposed to biological life, I agree. Shawn

	#11
Androcles	Re: Definition of the sun's "death"? "Double-A" <double-aa@hush.ai> wrote in message news:1184337290.253768.63600@i13g2000prf.googlegro ups.com... : On Jul 13, 6:09 am, "N:dlzc D:aol T:com \(dlzc\)" <d...@aol.com> : wrote: : > Dear tony_flanders: : > : > <tony_fland...@yahoo.com> wrote in message : > : > news:1184331265.571374.137330@n60g2000hse.googlegr oups.com... : > : > > On Jul 13, 12:33 am, Radium <gluceg...@gmail.com> wrote: : > : > >> I just don't understand why the expansion of the sun : > >> into a red giant would be classified as the sun's 'death'. : > >> ... : > >> My definition of the "death of the sun", is when the sun : > >> ceases its nuclear fusion. : > : > > I agree; it's sloppy terminology. A better term might be : > > death throes. But even that I'd save for the truly : > > terminal phase when the Sun creates a planetary : > > nebula. The red-giant phase would better be called : > > old age. : > : > How about "menopausal"? ;>) : > : > > Of course, stars continue to shine quite nicely even : > > after nuclear fusion has stopped. I would call a : > > white dwarf moribund rather than dead. : > : > David A. Smith : : Why do we insist on using such anthropomorphic terminology anyway? : Objects in space don't get born, live, and then die, they transition : from one kind of object into another. When we apply the terms of : carbon based life forms to inanimate objects, we are being completely : arbitrary. Otherwise, when a super massive star collapses, why not : say, "A black hole is born!"? Black hole... a snake swallowing its own tail. Possibly a neutron body... the nuclei, protons and electrons compressed under gravity at the core; but at the surface, cold evaporation to leave huge clouds of hydrogen light years across and talking billions of years to form, http://antwrp.gsfc.nasa.gov/apod/ap070106.html which slowly absorb radiation from other stars before condensing again to complete the cycle, the conclusion being a universe that always was and always will be. The core? Planets such as the Earth would fit the description rather well with its abundance of heavy elements. "Beginning" and "ending" are also anthropomorphisms, yet life itself is cyclic, energy driven, so why should not the universe be so as well? Big Bangs and black holes are rather silly theories, that's all. If there were a big bang there'd be a detectable point from which everything radiated, yet even the CMBR is homogeneous. http://antwrp.gsfc.nasa.gov/apod/ap061007.html And then there is this: http://antwrp.gsfc.nasa.gov/apod/ap061008.html The evidence for either wild conjecture simply isn't there, we must examine the universe from ALL the data before we can call ourselves scientists.

	#12
Odysseus	Re: Definition of the sun's "death"? In article <LADli.26938$Fc.8903@attbi_s21>, Sam Wormley <swormley1@mchsi.com> wrote: <snip> > Your book has an excellent diagram on page 459 relating the original > star mass to that of the final core mass (core mass being the mass of > whats left of the star at the end of its evolutionary processes). What book is that? I assume your posting was taken from class notes -- what course? -- Odysseus

	#13
Tom Kerr	Re: Definition of the sun's "death"? In article <odysseus1479-at-3033AE.03080814072007@news.telus.net>, Odysseus <odysseus1479-at@yahoo-dot.ca> wrote: >In article <LADli.26938$Fc.8903@attbi_s21>, > Sam Wormley <swormley1@mchsi.com> wrote: > ><snip> > >> Your book has an excellent diagram on page 459 relating the original >> star mass to that of the final core mass (core mass being the mass of >> whats left of the star at the end of its evolutionary processes). > >What book is that? I assume your posting was taken from class notes -- >what course? Glad I wasn't the only one wondering about this. I looked at the thread and other possibly related threads and couldn't work out what the reference to "your book" was all about. I'd like to find out as well.

	#16
Stuart Chapman	Re: Definition of the sun's "death"? Sam Wormley wrote: > Radium wrote: >> Hi: >> >> I just don't understand why the expansion of the sun into a red giant >> would be classified as the sun's 'death'. As a red giant, the sun will >> very much be alive as it is today. It will burn helium instead of the >> hydrogen it burns today. >> >> My definition of the "death of the sun", is when the sun ceases its >> nuclear fusion. Fusion is what gives the sun its life. >> >> >> Best, >> >> Radium >> > > Stars spend the majority of their "lives" on the main sequence, i.e., > fusing hydrogen into helium. and the secondary, tertiary, etc. fusion > processes are short lived by comparison. > > Star are born and stars die... just like us. The big massive stars have > but short lives, a few millions of years. Stars like our sun last for a > good 10 billions of years, and the little red stars like Barnard's Star > might last for 100 billion years. How long stars live, is determined by > their mass (which must be at least 80 Jupiter masses to sustain > thermonuclear fusion of hydrogen). > > There are four (4) fates for the end of stars depending on their masses > and the masses of their cores: > > Red/Brown Dwarfs - less than 0.6 Ms <== Main Sequence 0.076-0.8 Ms > Stars less than about 0.6 solar masses, when nuclear fuel is used up, > gravitational collapse shrinks the star, but no more than the gas > temperature-pressure-volume laws of classical physics allow. We have > not found any white dwarf less massive than 0.6 solar masses. Part of > the answer is that the universe may not be old enough for lower mass > stars to have evolved off the main sequence. > > White Dwarfs - 0.6 and 1.44 Ms <== Main Sequence 0.8-8 Ms > Stars with core masses between 0.6 and 1.44 solar masses are > destined to become white dwarfs. White dwarfs are degenerate matter. > Further collapse is halted by electron degeneracy pressure. See pages > 456-459 in your textbook. The vast majority of stars are in this mass > range and are destined to become white dwarfs > > Neutron Stars - 1.44 and 2.9 Ms <== Main Sequence 8-30 Ms > Core masses between 1.44 and 2.9 solar masses overcome electron > degeneracy pressure and collapse to form neutron stars, a star that is > essentially one gigantic nucleus. Further collapse is halted by neutron > degeneracy pressure. > > Black Holes - 3 or more Ms <== Main Sequence > 30 Ms > But for cores with mass of 3 or more solar masses, neutron > degeneracy pressure does not stop the collapse and the star becomes a > black hole with zero physical size, but with all the mass. Gravity > really wins! > > In each case, gravity eventually wins, but, to what extent is > determined by the mass and the relative pressures of the quantum > mechanical forces, electron and neutron degeneracy pressure. Your book > has an excellent diagram on page 459 relating the original star mass to > that of the final core mass (core mass being the mass of whats left of > the star at the end of its evolutionary processes). Something I'd like to know: Just what will be left of a star (that won't explode into a neutron star or black hole) some 20 billion years from now. A cold, spinning sphere of iron that you could walk on? All stellar 'histories' that I have read (maybe I should say understood), don't seem to elaborate on this. As for the neutron star: Has there been any speculation as to how this would appear if you could orbit one from a safe distance? -- Stupot http://insignity.blogspot.com

	#18
Norbert	Re: Definition of the sun's "death"? Stuart Chapman nous a donc écrit : > Something I'd like to know: > > Just what will be left of a star (that won't explode into a neutron > star or black hole) some 20 billion years from now. A cold, spinning > sphere of iron that you could walk on? Not iron. Degenerate electronic matter is the constituent of a white dwarf. Don't ask me the aspect of this matter You could obviously walk on it, if you are not crushed by gravitation. And in 20 billion years, this sphere of matter will surely be as cold as the rest of the universe. > > All stellar 'histories' that I have read (maybe I should say > understood), don't seem to elaborate on this. > > As for the neutron star: Has there been any speculation as to how this > would appear if you could orbit one from a safe distance? You could refer to this page http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html where you will find some animation films about travelling to a neutron star. The aspect of a neutron star must be a (quite) perfect sphere of iron, which forms the crust of the star. -- Norbert. (no X for the answer) ====================================== knowing the universe - stellar and galaxies evolution http://nrumiano.free.fr images of the sky http://images.ciel.free.fr ======================================

	#23
Martin Brown	Re: Definition of the sun's "death"? On Jul 16, 3:06 pm, "Norbert" <Xnorbert.rumi...@numericable.frX> wrote: > Stuart Chapman nous a donc écrit : > > > Something I'd like to know: > > > Just what will be left of a star (that won't explode into a neutron > > star or black hole) some 20 billion years from now. A cold, spinning > > sphere of iron that you could walk on? > > Not iron. Degenerate electronic matter is the constituent of a white dwarf. > Don't ask me the aspect of this matter Mostly at the surface chemically it will be carbon and oxygen when it cools down enough to recombine from a plasma. And crystallisation is believed to play a part in the cooling of white dwarfs when the surface temperature falls below about 6000K (typically 5x10^9 years after formation). > You could obviously walk on it, if you are not crushed by gravitation. > And in 20 billion years, this sphere of matter will surely be as cold as the > rest of the universe. I think I would prefer to wait about 10^12 years for it to cool. By then if current theories are correct it will be a roughly Earth sized diamond with an iron core and very unpleasantly strong surface gravity. Various ZZ Cetae type white dwarf type stars are being studied to try and understand their cooling processes. eg http://www.aas.org/publications/baas...aas203/181.htm more popular version http://news.bbc.co.uk/1/hi/sci/tech/3492919.stm Regards, Martin Brown