# of star generations needed to produce observed element abundances
te...@intex.com
Just a quick question - I frequently read in popular science level
astronomy books that we humans are made of star matter - i.e., that the
carbon, oxygen, and other elements beyond helium are made via supernova
and so these high Z elements would not be in abundance until some # of
supernova had occurred.
My question is this - approximately how many "generations" of stars
needed to supernova to produce the observed abundances of high Z
elements currently observed? Since stars have different lifetimes (and
I seem to recall reading that early stars were quite large and had much
shorter life times), I understand that the term "generation" is not
quite right but didn't know what else to call it?
My second question is this - on earth we have a distilled amount of
high Z atoms. Is this density consistent with what was available in
the proto star that eventually became the sun and the planets? It
would seem it must but I was wondering if anyone has observations that
confirm this from other star systems.
Thanks,
Ted
Jonathan Thornburg -- remove -animal to reply
> My question is this - approximately how many "generations" of stars
> needed to supernova to produce the observed abundances of high Z
This isn't an answer to your question, but rather a more general
comment: There's an article about (indirect) observations of the
first stars, as well as a commentary, in the 3.Nov.2005 issue of
Nature. Right now I can view it via the url
http://www.nature.com/nature/journal/v438/n7064/edsumm/e051103-08.html
but I don't know whether this works outside an institution with an
institutional subscription. I think "fair use" does permit me to
quote the following "Editor's summary":
The most distant and oldest observable stars are in the metal-rich
galaxies seen in images such as the Hubble ultra-deep field. The metal
which in cosmology is anything that's not hydrogen or helium must have
come from somewhere and as nucleosynthesis happens in stars, there must
have been an earlier population of metal-free stars. No existing or
planned telescopes can detect them individually, but evidence of their
existence has been found hidden in images obtained by the Infrared Array
Camera onboard NASA's Spitzer Space Telescope. After removing foreground
stars and galaxies from the image, the tiny fluctuations that remain in
the cosmic infrared background are the fossil of emissions from the old
metal-free stars.
Enjoy,
--
-- "Jonathan Thornburg (remove -animal to reply)" <jth...@aei.mpg-zebra.de>
Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam
David M. Palmer
<te...@intex.com> wrote:
> Hi,
>
> Just a quick question - I frequently read in popular science level
> astronomy books that we humans are made of star matter - i.e., that the
> carbon, oxygen, and other elements beyond helium are made via supernova
> and so these high Z elements would not be in abundance until some # of
> supernova had occurred.
You need supernovae to get iron and above, but most carbon, oxygen,
etc. actually comes from stellar winds from Asymptotic Giant Branch
(AGB) stars and planetary nebulae (although you get some from
supernovae as well). Still star stuff, and very pretty, even if not as
bright as a supernova.
http://antwrp.gsfc.nasa.gov/apod/ap050924.html
--
David M. Palmer dmpa...@email.com (formerly @clark.net, @ematic.com)
oriel36
Due to the observational data emerging from the supernova SN1987A
there are indications that stellar evolution needs to be adjusted from
present conceptions.
I have a copyright from 1990 indicating two external bounday rings with
a smaller central ring at the intersection which in turn is parallel
with the supernova star.Considering that the rings were observed in
1994,I am rightly proud of my work relating to the process of stellar
collapse.
http://th.nao.ac.jp/openhouse/1998/vrml/scene4/sn1987a.jpg
The abundance of different types of elements on this planet may be
due to the stellar evolution of our parent star with remnants of the
original stellar evolution event still in our neighborhood.Rather than
stellar birth to stellar death,there may be other stages involved that
so far have yet to emerge.As my speciality is not stellar processes but
rather the geometric modelling of celestial structures by using cycles
and the lessons learned from heliocentricity,perhaps an enterprising
participant will look further into the conception.
[Mod. note: they might like to begin by asking how far the Sun has
moved since it was formed -- mjh]
Jonathan Silverlight
<geraldk...@yahoo.com> writes
>te...@intex.com wrote:
>
>> Hi,
>>
>> Just a quick question - I frequently read in popular science level
>> astronomy books that we humans are made of star matter - i.e., that the
>> carbon, oxygen, and other elements beyond helium are made via supernova
>> and so these high Z elements would not be in abundance until some # of
>> supernova had occurred.
>>
>
>there are indications that stellar evolution needs to be adjusted from
>present conceptions.
>
>I have a copyright from 1990 indicating two external bounday rings with
>a smaller central ring at the intersection which in turn is parallel
>with the supernova star.Considering that the rings were observed in
>1994,I am rightly proud of my work relating to the process of stellar
>collapse.
What exactly does "hold a copyright" mean? Has this been published
anywhere?
Aidan Karley
> My question is this - approximately how many "generations" of stars
> needed to supernova to produce the observed abundances of high Z
> elements currently observed?
>
assumptions about (or using a model that addresses) the degree of
mixing between (super)nova ejecta and unmodified big bang material. And
any realistic model will produce patchiness.
--
Aidan Karley,
Aberdeen, Scotland,
Location: +57d10' , -02d09' (sub-tropical Aberdeen), 0.021233
Written at Tue, 15 Nov 2005 13:57 GMT
[MOD: did I get the MIME damage in the signature sorted?]
te...@intex.com
I'm looking for a back of the envelope kind approximation.
For example, if we assume some model for supernova explosions, how many
of these explosions (or what rate of supernova explosions) would we
need to explain the high Z atom abundances? Then, we can ask the
question of whether this # is consistent with the observed distribution
of star masses that we could expect to supernova.
Steve Willner
te...@intex.com writes:
> My question is this - approximately how many "generations" of stars
> needed to supernova to produce the observed abundances of high Z
> elements currently observed?
Suppose you start with 3000 solar masses of hydrogen gas. At current
star formation efficiency, you might form 30 solar masses of stars.
In the early Universe, with an initial mass function strongly biased
to high masses, this might consist of just a single star. This star
would become a supernova, and you might get a solar mass of heavy
elements out of it. This is already enough to give the heavy element
abundances seen in globular clusters. If you want the _solar_ metal
abundance, though, you need something like 100 more generations of
processing, especially as the IMF will produce lots more low-mass
stars after the first few generations (we think!).
Of course what I've left out is that not all the hydrogen gas will
collapse into star-forming clumps. But on the other hand, the star
formation efficiency in the early Universe might have been a lot
higher than what we see today. So the above is really rough; the
true answer is that nobody knows for sure. It is a topic of very
active research, but I think the answer won't be known until JWST
data come in.
> My second question is this - on earth we have a distilled amount of
> high Z atoms. Is this density consistent with what was available in
> the proto star that eventually became the sun and the planets?
The early solar nebula is thought to have been mostly hydrogen and
helium, like the Sun is today. Most of the hydrogen and helium have
escaped.
--
Steve Willner Phone 617-495-7123 swil...@cfa.harvard.edu
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)
te...@intex.com
> In article <mt2.0-5182...@hercules.herts.ac.uk>,
> te...@intex.com writes:
> > My question is this - approximately how many "generations" of stars
> > needed to supernova to produce the observed abundances of high Z
> > elements currently observed?
>
> Suppose you start with 3000 solar masses of hydrogen gas. At current
> star formation efficiency, you might form 30 solar masses of stars.
> In the early Universe, with an initial mass function strongly biased
> to high masses, this might consist of just a single star. This star
> would become a supernova, and you might get a solar mass of heavy
> elements out of it. This is already enough to give the heavy element
> abundances seen in globular clusters. If you want the _solar_ metal
> abundance, though, you need something like 100 more generations of
> processing, especially as the IMF will produce lots more low-mass
> stars after the first few generations (we think!).
What's the approximate lifetime of these stars and is there currently
any conflict between the current solar metal abundances and the
# of generations needed to produce the abundance? There could either
have been too few generations or perhaps even too many (and so we
should
expect even higher abundances?
Thanks,
Ted
Steve Willner
No one knows. Might be a short as 1E6 years if they are as massive
as 100 solar masses. As I wrote earlier, the initial mass function
is not known. Stellar lifetime depends strongly on mass, and it's a
mistake to think lifetime will be the same for all stars of a given
"generation," which itself is a misleading term.
> and is there currently
> any conflict between the current solar metal abundances and the
> # of generations needed to produce the abundance?
I don't think there is any great problem with the Sun, which after
all didn't form until the Universe was already 8E9 years old. That
said, the chemical evolution of the Universe is far from understood.
Even for a local galaxy such as M33, metallicity versus radius is in
doubt. This probably reflects some lack of understanding of how the
metals were formed, though systematic errors in the observations
cannot be ruled out.
Perhaps more mysterious, at z=6, when the Universe was only 1E9 years
old, at least some galaxies already had metallicity not far below
solar. And I am pretty sure the "G-subdwarf problem" has been
mentioned before on this newsgroup.
Try asking again after JWST has been working a few years.
Jonathan Silverlight
<wil...@cfa.harvard.edu> writes
>
>Perhaps more mysterious, at z=6, when the Universe was only 1E9 years
>old, at least some galaxies already had metallicity not far below
>solar. And I am pretty sure the "G-subdwarf problem" has been
>mentioned before on this newsgroup.
>
>Try asking again after JWST has been working a few years.
>
Assuming it gets off the ground.
--
Mail to jsilverlight AT merseia DOT fsnet DOT CO dot UK is more likely to be
seen!
te...@intex.com
- for
this topic?
Thanks,
Ted