PLANETARY NEBULAE : Part 5
Letters Regarding Planetary Nebula
and Evolution Theory
I N T R O D U C T I O N
On 11th July 1997, Dr. Jessica Chapman of the Anglo-Australian
Telescope (AAO) addressed the Astronomical Society of New South
Wales on the interesting topic of ‘The Life and Death of Stars’. Within this poignant talk, she discussed
within this talk the asymptotic giant branch phase (AGB) and
the specific area of the formation of planetary nebulae.
Unfortunately due to time constrictions at the venue, at the time,
Dr. Chapman did not have enough time to formally discuss some of the
ideas expressed within her talk. As we have are talking about
planetaries, some additional important points were raised in a
personal communication about some glaring discrepancies with
information often published in popular books and magazines. I thought
that the following could be of some interest to readers here.
A major question that was bugging me for more than
years at the time was;
Will the Sun Really Form a Planetary
Most common books and articles, (including my
presentation and text), as recent as August 1997 either state nothing
or will still state this incorrectly — the Sun will form a
First Letter Written to Dr. Chapman
Thank you for your address at the Astronomical Society of NSW last
Friday night on Asymtopic Giant Stars. It was certainly an enjoyable
lecture, and also obtained a good general response. I am sorry that
the circumstances of occupying the hall made everything so rushed,
and had little time to talk to you.
In summary:- I have been an adult education teacher for the last
ten years, and am interested in the general topic of stellar
evolution. I have found that most topics within this subject are
usually easily to explain. This is made using the H-R Diagrams and a
series of slides — from the birth of stars to their deaths as
either supernovae (SN’s), neutron stars
and white dwarfs. ( N.B. The level that I am teaching is similar to
many portions of your lecture.)
In regards, planetaries I have been explaining (with suitable
given text) that the progenitors generally are between 4.0 and 8.0
M⊙, producing WD’s 0.7 M⊙
to 1.3 M⊙. This data is based primarily (and elsewhere) on
Iben, I. Jr. article in the QJRAS Vol.26, entitled “Life and Times of an Intermediate Mass
Stars — in Isolation/in a Close Binary.” This I was recommended by other
In the literature I have searched (till Jan 1997), this range of
the original progenitors is as low as 1.5 M⊙, with the upper
limit around 10 M⊙. The only general text I know about that
discusses mass ranges in any detail is Ken Croswell “The Alchemy of the Heavens” (1996).
I posed the following
questions and below are her replies;
1. What is the mass range of the progenitors of
planetaries in current theory prior to the AGB (Asymptotic Giant
The mass range is not well determined but the
minimum mass is below one solar mass while the upper mass is
currently thought to be between 6 and 8 solar masses. The lower and
upper limits are difficult to pin down precisely as the evolutionary
models depend critically on things like the stellar metallicies and
on the rate and duration of mass-loss in the AGB phase.
2. As the mass increases within this range, is
their any known correlation between the structures observed in the PN
to the amount of gas ejected in the AGB phase as seen in the
illuminated circumstellar envelope?
Good question — I wish I knew the answer to
this. About half of planetary nebulae show non-spherical shapes. I
don’t think there is a known correlation though between shape
and progenitor mass. In some cases the asymmetries (especially
bipolarity) may be caused by binary companions. In other cases its
thought to be related to an enhancement of a small density variation
in the AGB phase which gets ‘amplified’ in
the post-AGB phase. The stellar magnetic fields may also play a role
— though no-one has yet proved this.
3. What is the minimum mass suggested for the mass
of the PNN — that does not have enough UV energy to illuminate
the circumstellar envelope?
As above — I’m
not sure exactly but well below 1 solar mass.
4. In current theory, does Sun produce a (proto-)
5. Could you also suggest other authors that may
assist in this subject (Other than Iben.)
Here’s a list of some
related research papers. Most of these are heavy going but have
useful tables or diagrams.
- Chapman J.M. & Cohen R.J., “The
Circumstellar Envelope of VX Sgr.”,
MNRAS, 220, 513 (1986) — A detailed radio maser
study of mine.
- Bedijn P.J., “Pulsation,
Mass-Loss and Evolution of AGB Stars.” A&A., 205, 105 (1988)
— Bedijn’s work produced many of
the current ideas on AGB evolution.
- Vassiliadas and Wood, “Evolution
of Low and Intermediate Mass Stars to the End of the AGB.” AJ., 413, 641 (1993) —
Probably best current paper on this topic.
- Vassiliadas and Wood; “Post-AGB
Evolution of Low and Intermediate Mass Stars.”, AJ.Sup.Ser., 92, 125 (1994)
— On evolution from AGB to PN and white dwarfs.
- Habing H.J. “Circumstellar
Envelopes and AGB Stars.”
A&A.Review, 7, 97 (1996) — Good review paper
with hundreds of references.
Second Letter Regarding Planetary Nebula
and Evolution Theory
It is interesting to note that the text published in so many
general sources are wrong in their presentation on the formation and
evolution on PN’s. If I may suggest,
this information should be directly available for educational
purposes. One of the most important aspects in teaching in evolution
theory in astronomy is the relationship of the Sun to the other
stars. Most of the text that I am aware of never actually state that
the Sun will produce a planetary nebula, and if it does, the detail
explaining this is often minor.
At present, a popularized article is well in order. An article in
a magazine like Sky and Telescope maybe a suitable place for an
overview. If you know of someone in the AAO staff who could right
such an article, this maybe a good idea to publish — besides,
it would make good publicity for the AAO!
If I should be so bold, a final suggestion for your ‘popular’
presentations of your Research is the relationship to the discards of
the AGB phase of stars to the formation of elements essential to life
and planetary formation. (Carl Sagan’s
‘Star Stuff’.) In education, this gives a ‘personal’
relationship to the evolution of stars. More importantly, if the Sun
does produce a planetary nebula — this gives a visual and
understandable relationship to the spectacular images of PN’s, like those of David Malin.
Again, thank you for you very much for your time, and best wishes
for the Research projects that you follow in the future.
Regards, Andrew James
I should perhaps have told you that I did in fact write up a
popular article on just this topic — for the Australian Sky and
Space magazine. I think the issue was December 95. I’ve also seen other good popular articles on
stellar evolution in the American Sky and Telescope magazine.
The whole field of mass-loss from stars is very recent. The
importance of mass-loss has only been recognised within the last 20
years and many of the details (I.e. structures / mass-ranges) are not
yet properly understood. It is irritating that most of the popular
text books present very out of date ideas on this topic though it
does take time for front-line research to become properly known in
the popular literature. Personally I try to give occasional popular
talks on my own research as do many of my colleagues. Probably the
best source for more recent information is the magazines, especially
Scientific American and I think you can send them enquiries for past
issues on selected topics.
Best wishes, Jessica
This appeared in “Neat Southern
Planetaries“ that appeared in the
in 1999 as an endnote in “Neat
Southern Planetaries : Part 5.”
Last Update : 27th November 2011
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