Stellar Magnetic Fields

I have noticed something that I think is quite interesting concerning
the Global Surface Dipole B Fields of stars that have measurable B
fields.

White Dwarf: R ~ 10^9 cm; B ~10^6 G

Red Dwarf: R ~ 10^10 cm; B ~ 10^4 G

F-G-K "Dwarfs": R ~ 10^11 cm; B ~ 10^2 G

Red Giants: R ~/ 10^12 cm; B ~/ 1 G

The pattern is like a 1/R^2 progression.

IF there were Kerr-Newman objects at the center of stars, with R ~
10^5.5 cm and B ~ 10^13 G, then the surface dipole B fields for the
stars would just be the 1/R^2 values of the central field.

It has not escaped my attention that neutron star-like objects would
make rather efficient nucleating objects for the formation of stars.

This is an unorthodox and speculative idea, but consider that star
formation and the explanation of stellar surface B fields are two
major unresolved problems in astrophysics.

When a star goes supernova, what's left behind? Right an ultracompact
object with an radius not far from 10^5.5 cm and an average B of about
10^13 G.

Worth considering objectively, I think.

RLO
www.amherst.edu/~rloldershaw

In article , "Robert L.
Oldershaw" writes:

I have noticed something that I think is quite interesting concerning
the Global Surface Dipole B Fields of stars that have measurable B
fields.

The pattern is like a 1/R^2 progression.

Which is rather generic and probably easy to reproduce by various means.

IF there were Kerr-Newman objects at the center of stars, with R ~
10^5.5 cm and B ~ 10^13 G, then the surface dipole B fields for the
stars would just be the 1/R^2 values of the central field.

This is taking a data set and retroactively fitting some adjustable
parameters to match. Shouldn't a theory PREDICT stuff? What use is a
theory with adjustable parameters so that one can fit various data sets
by adjusting the parameters?

It has not escaped my attention that neutron star-like objects would
make rather efficient nucleating objects for the formation of stars.

How did the first neutron-star like objects form?

This is an unorthodox and speculative idea, but consider that star
formation and the explanation of stellar surface B fields are two
major unresolved problems in astrophysics.

I don't know much about the second but the first is not a major
unresolved problem. Sure, not all the details are known, but the basic
stuff has been known for decades.

When a star goes supernova, what's left behind? Right an ultracompact
object with an radius not far from 10^5.5 cm and an average B of about
10^13 G.

Keep in mind that no-one has actually observed this; it is a conclusion
based on the models of stellar structure and evolution which, above, you
seem rather comfortable about doubting.

On Nov 19, 9:04*am, "Robert L. Oldershaw"
wrote:
I have noticed something that I think is quite interesting concerning
the Global Surface Dipole B Fields of stars that have measurable B
fields.

White Dwarf: R ~ 10^9 cm; B ~10^6 G

Red Dwarf: R ~ 10^10 cm; B ~ 10^4 G

F-G-K "Dwarfs": R ~ 10^11 cm; B ~ 10^2 G

Red Giants: R ~/ 10^12 cm; B ~/ 1 G

The pattern is like a 1/R^2 progression.

Where did you get these R/B figures from? If you look for instance at
http://en.wikipedia.org/wiki/White_dwarf , then you can find there
that the magnetic field of white dwarfs can differ by many orders of
magnitude. So it seems you have been rather selective here in order to
establish the 1/R^2 relationship.

The point is that, independently of the radius, the magnetic field
should definitely depend on the rotational frequency of the star as
well (what is needed for a magnetic field in general is a current, and
you should always get a current if you have a rotating plasma, as the
electrons and protons have different masses and thus will respond
differently to the centrifugal force, and there will thus be a very
slight differential rotation of the positive and negative charges,
i.e. a current and thus a magnetic field).

Following this idea, I looked a while ago I looked into the magnetic
field of the planets, and found that the difference between the
Earth's and Jupiter's magnetic momenta seems indeed to be explained if
one assumes it is associated with the centrifugal force acting on the
matter in its (fluid or gaseous) interior, i.e. if one takes it as
proportional to the centrifugal force of the planet or star

F= M* w^2 *R ,

where M is the total mass, w the angular rotational frequency and R
the radius (give or take a constant factor).

As mentioned, F would determine the magnetic moment. The surface
magnetic field would then decrease with a further factor 1/R^3 (dipole
field), so B would go like

B ~ M * w^2 *1/R^2 .

So the surface magnetic field should not just be given by the 1/R^2
behaviour but also by the angular rotation frequency w and the mass M.

Thomas

Thomas Smid wrote:
Where did you get these R/B figures from? If you look for instance at
http://en.wikipedia.org/wiki/White_dwarf , then you can find there
that the magnetic field of white dwarfs can differ by many orders of
magnitude. So it seems you have been rather selective here in order to
establish the 1/R^2 relationship.

Moreover, for the one case for which we have excellent data (the Sun),
the magnetic field on a stellar surface is highly variable in both
space and time, in ways which don't accord well with the magnetic
field of a Kerr-Newman black hole. Magnetic fields of other stars
are also known to vary a lot over space and time, although our data
for other stars doesn't have the spatial resolution that we have for
the Sun.

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
"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

At this point I would like to refine the R and B estimates used to
arrive at the 1/R^2 scaling for the global dipole B fields of
"magnetic" subclasses of several major classes of stars.

The equation under consideration is: B = B* / (R/R*)^2 , where
the * designates the average values of B and R for neutron stars.

In log form the equation is: log B = 13.25 - 2 log R/R*

For neutron stars: log R* = 6.0 and log B* = 13.25

For white dwarf stars: log R = 9.0 and log B = 6.0

For M dwarfs: log R = 10.3 and log B = 3.5

For beta Cepheids: log R = 11.3 and log B = 2.2

For O,B,A,F,G Giant stars: log R = 11.9 and log B = 0

When you plot this up, you get a straight line that is approximated by
the log equation given above.

If one should doubt that the R and B values I use are appropriate,
I would appreciate being directed to empirical data that would suggest
other R and B values that might be more appropriate.

Happy Holidays,
RLO
www.amherst.edu/~rloldershaw

[[Mod. note -- I've taken the liberty of changing the subject line from
" Stellar Magnetic Fields" to "planetary nebulaa and neutron stars",
since this article really doesn't have much to do with stellar magnetic
fields.
-- jt]]

If you read "Central Stars of Planetary Nebulae:...catalogue" which
can be obtained at this link: http://arxiv.org/PS_cache/arxiv/pdf/...010.5376v1.pdf
,

then you know that:

(1) of roughly 3,000 PNs that are known, the majority of their central
stars have not been identified and spectroscopically studied,
and
(2) of the the central stars that have been studied, a significant
percent are classified as "blue" objects.

Isolated neutron stars have been observed optically, for example see:
http://iopscience.iop.org/1538-4357/..._588_1_L33.pdf
and the Nature paper of 1997 by Walter and Matthews. One can also
search on Mignani's research on the spectroscopy of neutron stars via
arxiv.org.

The main point is that the above references note that neutron stars
are observed as being very "blue" objects when they can be observed in
the optical range.

My question, and here I need more than a little help from experienced
astrophysicists, is as follows. Could the "blue" objects at the
centers of many (some) planetary nebulae be neutron stars? If one
compares the spectroscopic (and other) data for the two classes of
"blue" objects, might there be a provocative overlap?

If there is a significant overlap, then I think we have something to
write home about, so to speak.

Happy New Year (but I suggest that you drink fine coffee instead of
that crankcase oil),
RLO
www.amherst.edu/~rloldershaw

In article
,
"Robert L. Oldershaw" writes:

(1) of roughly 3,000 PNs that are known, the majority of their central
stars have not been identified and spectroscopically studied,

OK.

and
(2) of the the central stars that have been studied, a significant
percent are classified as "blue" objects.

OK.

Isolated neutron stars have been observed optically, for example see:
http://iopscience.iop.org/1538-4357/..._588_1_L33.pdf
and the Nature paper of 1997 by Walter and Matthews. One can also
search on Mignani's research on the spectroscopy of neutron stars via
arxiv.org.

The main point is that the above references note that neutron stars
are observed as being very "blue" objects when they can be observed in
the optical range.

OK.

My question, and here I need more than a little help from experienced
astrophysicists, is as follows. Could the "blue" objects at the
centers of many (some) planetary nebulae be neutron stars? If one
compares the spectroscopic (and other) data for the two classes of
"blue" objects, might there be a provocative overlap?

If there is a significant overlap, then I think we have something to
write home about, so to speak.

Save your stationery. Most have not been observed. Some have been
observed. Neutron stars are blue. It's a big jump to assume that the
unobserved ones are neutron stars. Lots of stellar objects are blue.
More significantly, those that have been observed are NOT neutron stars.

I don't know who owns most of the expensive cars in my town. The few
owners I do know are rich. NBA players are rich. Should I assume that
most of the expensive cars in my town are owned by NBA players?

On Jan 3, 11:15 pm, (Phillip Helbig---
undress to reply) wrote:

I don't know who owns most of the expensive cars in my town. The few
owners I do know are rich. NBA players are rich. Should I assume that
most of the expensive cars in my town are owned by NBA players?


Be my guest. But these quaint analogies bear no resemblance to my
reasoning, thank you.


Save your stationery. Most have not been observed. Some have been
observed. Neutron stars are blue. It's a big jump to assume that the
unobserved ones are neutron stars. Lots of stellar objects are blue.
More significantly, those that have been observed are NOT neutron stars.

If one has an adequate understanding of the new paradigm I work
within, then one knows that I expect the overwhelming majority of PN
nuclei to compact high-temperature stars, as is observed in the small
fraction of PN nuclei that have been studied carefully.

The case wherein all of the original star's shells have been ejected,
leaving a bare neutron star-like nucleus, should be far less probable.
Perhaps only 1% to 10% of PNN will be of this type. So it is very
premature for you to assume that my prediction is ruled out. It most
certainly has not been ruled out, if we are deciding by scientific
methods.

The type of system I am predicting: a planetary nebula with a neutron
star-like nucleus will most likely be found at the center of faint
spherical PN such as the Soap Bubble Nebula PN G75.5+1.7, which was
mentioned earlier in this thread.

When we have characterized the PN nuclei of 100 faint systems, and at
least 100 of the more typical PN systems, then we will have enough
hard data to say with some scientific confidence, rather than bluster
or wishful thinking, whether or not there is a definite overlap
between the observed properties of isolated neutron stars and some PN
nuclei.

RLO
www.amherst.edu/~rloldershaw

PS: If anybody wants to see a graph showing that the B and B-max
values for various star classes fit my 1/R^2 conjecture rather well,
send me an email and I will attach the graph to the return email.

In article ,
"Robert L. Oldershaw" writes:
(2) of the the central stars that have been studied, a significant
percent are classified as "blue" objects.

"Blue" isn't quantitative, but all PN central stars should have
temperatures above 30000 K.

Could the "blue" objects at the
centers of many (some) planetary nebulae be neutron stars?

Nothing I know rules out a PN central star having a neutron star
companion, but I don't see how a neutron star (only a few km in
diameter) could produce enough ionizing photons to keep the nebula
ionized. Central star temperatures are known from the nebular line
ratios, so you can't do it just by cranking up the temperature.

This is aside from pretty good stellar evolution theory.

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