Re: escape velocity question

["L. R. Cartwright (Larry)" <physics@SCNC.CPS.K12.MI.US>]

> I will be forever in Larry's debt for allowing me the opportunity finally
> to quote from the book that has been glowering at me these many years:
> Chandrasekhar's Stellar Structure   (1939)

You're welcome, Brian.  That 1939 monograph was Chandra's very first,
culminating his remarkable work as grad student and newly-minted
scientist.  Do you have an original, or the re-edition from the 1960's?
The numbers have been fine-tuned a little over the years, but he had the
essence available to work with in the 20's-30's.

It does clearly show the error in my mass estimate, which I realized
shortly after I posted but haven't had time to clean up until now.  The
correct Eridani B mass is about 0.4 solar masses, which makes
R = 1.3E+07 m or about 2 earth-radii.  Escape velocity v = 8.6E+05 m/s
if the 37000 g we started with is correct.

The experimental documentation of Chandrasekhar's astrophysical theories
continues.  For example, read the University of Delaware report at
< http://www.udel.edu/PR/UpDate/98/16/cosmic.html >.

Best wishes,

Larry

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Larry Cartwright
Physics, Physical Science, Internet Teacher
Charlotte High School, 378 State Street, Charlotte MI 48813
<physics@scnc.cps.k12.mi.us> or <science@scnc.cps.k12.mi.us>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I am very good at learning from my mistakes.
Undoubtedly, I shall learn a great deal today.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On Mon, 15 Mar 1999, brian whatcott wrote:

> I will be forever in Larry's debt for allowing me the opportunity finally
> to quote from the book that has been glowering at me these many years:
> Chandrasekhar's Stellar Structure   (1939)
>
> He offers in Table 34d some leading data for white dwarfs, expressed
> as log comparisons with the relevant solar quantities:
>
> Name            logM    logL    logR
> Sun              0       0       0
> o2  Eri B       -0.35   -2.25   -1.74
>  Sirius B       -0.01   -2.52   -1.71
> Van Maanen #1   +0.53   -3.85   -2.05
>
> (M mass, L luminosity   R radius)
>
> Subrahmanyan was after all the person who originated the upper mass
> limit of helium core for white dwarfs equal to 1.44 Sun masses,
> beyond which they are destined to collapse he said.
> He also had something to say about stellar models which vary material
> density with radial depth.
>
> Brian
>
> brian whatcott <inet@intellisys.net>
> Altus OK
>
> At 17:40 3/15/99 -0500, Larry Cartwright wrote:
> > John, you have nicely resolved the order of magnitude error posed
> > originally. ... I think you have underestimated the white dwarf radius
> > slightly.
>
> > With g = 37000 * g_earth = 3.6E+05 m/s^2 and m = 1 solar mass =
> > 2.0E+30 kg, we get R = 1.9E+07 m or about triple the earth's radius.  If
> > you assume less mass, say 0.8 solar mass, you get a slightly smaller
> > radius, perhaps 1.7E+07 m but still over 2.5 earth radii.  This agrees
> > pretty well with what little wd radius data I have seen (e.g. Sirius B and
> > Procyon B);  2-3 times wider than Earth, smaller than Neptune.
> > ...
>
> > Larry Cartwright