Fate of Sun-like stars

It is said that the fate of yellow dwarfs is known observationally.
This is because the oldest stars in the Milky Way, in globular
clusters and Milky Way halo are currently burning out if they have
about slightly less than the mass of the Sun. An example of old,
Sunlike star near us is Arcturus

Now questions:

It seems that while a few white dwarfs like the Pup are heavier, very
many white dwarfs, like Keid B and Procyon B, with known masses, have
masses in a narrow range of 0,5...0,6 solar masses.

What is the reason? Is it something fundamental about the nature of
red giants, such that stars with wide range of initial masses end up
shedding various amounts of gas to end up as white dwarfs with masses
in a narrow range?

What happens to the rest of the mass? The lightest red giants, at
1,0...0,9 solar masses (the less massive orange dwarfs have not had
the time to burn out) have to end up as white dwarfs of 0,5...0,6
solar masses, shedding a minimum of 0,4 solar masses in the process.
This should set the minimum mass of a planetary nebula. Yet the
observed planetary nebulae are much lighter, at less than 0,1 solar
masses. What happens to the rest of the mass?

Sun is believed to have a thin convective envelope which contains just
0,02 solar masses, and massive stagnant interior, most of which is not
hot enough for protium fusion. Therefore the helium generated by Sun
does not spread around Sun to surface, but instead builds up near the
centre.
The outer layers of Sun are still hydrogen.

What do planetary nebulae consist of? Do they consist of hydrogen,
which never has been in the hot core of the star? Do helium and metals
created by the star stay in the white dwarf, or do any escape with
the planetary nebula?

It is said that the Sun would exhaust the protium in centre when just
0,1 solar masses have fused. Since the white dwarf remnant would be
0,5 solar masses, with no protium left, does it mean that 4/5 of the
total protium fused by the Sun would be fused at a high speed during a
short time period in the shells around the core of a red giant?

Does it mean that, since a star issues most of its total lifetime
light after main sequence, in a star cluster most of the total light
should come from the small fraction of stars which are currently red
giants, and that all red giants combined should outshine the combined
light of all stars left on main sequence?

On Sep 22, 5:22 am, Crown-Horned Snorkack
wrote:
It is said that the fate of yellow dwarfs is known observationally.
This is because the oldest stars in the Milky Way, in globular
clusters and Milky Way halo are currently burning out if they have
about slightly less than the mass of the Sun. An example of old,
Sunlike star near us is Arcturus

Now questions:

It seems that while a few white dwarfs like the Pup are heavier, very
many white dwarfs, like Keid B and Procyon B, with known masses, have
masses in a narrow range of 0,5...0,6 solar masses.

What is the reason? Is it something fundamental about the nature of
red giants, such that stars with wide range of initial masses end up
shedding various amounts of gas to end up as white dwarfs with masses
in a narrow range?

What happens to the rest of the mass? The lightest red giants, at
1,0...0,9 solar masses (the less massive orange dwarfs have not had
the time to burn out) have to end up as white dwarfs of 0,5...0,6
solar masses, shedding a minimum of 0,4 solar masses in the process.
This should set the minimum mass of a planetary nebula. Yet the
observed planetary nebulae are much lighter, at less than 0,1 solar
masses. What happens to the rest of the mass?

Sun is believed to have a thin convective envelope which contains just
0,02 solar masses, and massive stagnant interior, most of which is not
hot enough for protium fusion. Therefore the helium generated by Sun
does not spread around Sun to surface, but instead builds up near the
centre.
The outer layers of Sun are still hydrogen.

What do planetary nebulae consist of? Do they consist of hydrogen,
which never has been in the hot core of the star? Do helium and metals
created by the star stay in the white dwarf, or do any escape with
the planetary nebula?

It is said that the Sun would exhaust the protium in centre when just
0,1 solar masses have fused. Since the white dwarf remnant would be
0,5 solar masses, with no protium left, does it mean that 4/5 of the
total protium fused by the Sun would be fused at a high speed during a
short time period in the shells around the core of a red giant?

Does it mean that, since a star issues most of its total lifetime
light after main sequence, in a star cluster most of the total light
should come from the small fraction of stars which are currently red
giants, and that all red giants combined should outshine the combined
light of all stars left on main sequence?

My knowledge of this is very limited, but I think or at least guess
that supposedly a large percentage of a star's mass is supposed to be
shed as a planetary nebula, after the star has left the main sequence,
and that a higher percentage of the star's mass is shed, the more the
massive the star initially is, at least up to the point that the star
becomes massive enough to become a neutron star rather than a white
dwarf.

Also other factors in terms of the range of masses might be the simple
fact that less massive stars are more numerous than more massive
stars, and if a star is not massive enough, then it becomes not very
luminous, and so it becomes too long lived to form a white dwarf in
the time frame of only ten or so billion years.

On 24 sept, 11:38, wrote:
On Sep 22, 5:22 am, Crown-Horned Snorkack
wrote:



It is said that the fate of yellow dwarfs is known observationally.
This is because the oldest stars in the Milky Way, in globular
clusters and Milky Way halo are currently burning out if they have
about slightly less than the mass of the Sun. An example of old,
Sunlike star near us is Arcturus

Now questions:

It seems that while a few white dwarfs like the Pup are heavier, very
many white dwarfs, like Keid B and Procyon B, with known masses, have
masses in a narrow range of 0,5...0,6 solar masses.

What is the reason? Is it something fundamental about the nature of
red giants, such that stars with wide range of initial masses end up
shedding various amounts of gas to end up as white dwarfs with masses
in a narrow range?

What happens to the rest of the mass? The lightest red giants, at
1,0...0,9 solar masses (the less massive orange dwarfs have not had
the time to burn out) have to end up as white dwarfs of 0,5...0,6
solar masses, shedding a minimum of 0,4 solar masses in the process.
This should set the minimum mass of a planetary nebula. Yet the
observed planetary nebulae are much lighter, at less than 0,1 solar
masses. What happens to the rest of the mass?

Sun is believed to have a thin convective envelope which contains just
0,02 solar masses, and massive stagnant interior, most of which is not
hot enough for protium fusion. Therefore the helium generated by Sun
does not spread around Sun to surface, but instead builds up near the
centre.
The outer layers of Sun are still hydrogen.

What do planetary nebulae consist of? Do they consist of hydrogen,
which never has been in the hot core of the star? Do helium and metals
created by the star stay in the white dwarf, or do any escape with
the planetary nebula?

It is said that the Sun would exhaust the protium in centre when just
0,1 solar masses have fused. Since the white dwarf remnant would be
0,5 solar masses, with no protium left, does it mean that 4/5 of the
total protium fused by the Sun would be fused at a high speed during a
short time period in the shells around the core of a red giant?

Does it mean that, since a star issues most of its total lifetime
light after main sequence, in a star cluster most of the total light
should come from the small fraction of stars which are currently red
giants, and that all red giants combined should outshine the combined
light of all stars left on main sequence?

My knowledge of this is very limited, but I think or at least guess
that supposedly a large percentage of a star's mass is supposed to be
shed as a planetary nebula,

Do we see that mass in the observed planetary nebulae?

after the star has left the main sequence,
and that a higher percentage of the star's mass is shed, the more the
massive the star initially is, at least up to the point that the star
becomes massive enough to become a neutron star rather than a white
dwarf.

Also other factors in terms of the range of masses might be the simple
fact that less massive stars are more numerous than more massive
stars, and if a star is not massive enough, then it becomes not very
luminous, and so it becomes too long lived to form a white dwarf in
the time frame of only ten or so billion years.

Ah yes. Then we have the range from the least massive stars to have
burned out - Sunlike and slightly less - to the more massive ones.

Procyon B had to be more massive than Procyon A. And we know the mass
of A. What was the original mass of Procyon B?