Re: CMBR and neutron stars

SW> Thus as of today (and barring an error somewhere), it looks as
SW> though
SW> stellar light is 3 to 10% of the total radiation in the
SW> Universe.

In article <sbxOe.124446$E95.76067@fed1read01>,
"N:dlzc D:aol T:com \(dlzc\)" <N: dlzc1 D:cox T:net@xxxxxxxxxx> writes:
> ... for a position similar to our own.

No, the numbers in my previous post for "extragalactic background
light" were for a position far from any local light source. From
Earth, looking towards the Galactic pole, the brightness of stars
fainter than mag 6 corresponds to about 110 nW m^-2 sr^-1 in visible
light alone. You would have to add to that a considerable infrared
contribution, and of course the brightness is much greater at lower
Galactic latitudes.

> Stellar light would likely be lower for a lone BH in deep space,

See above. The EBL is the minimum.

> > SW> Thus the relative contribution from stars increases with
> > time.
>
> Actually no, it would not, since the Universe is expanding.

You didn't read carefully. Expansion affects both the microwave
background and existing starlight equally, but stars keep pumping out
new light. To see the result, imagine we could instantly "turn off"
all stars in the Universe. Then at all future times, the ratio of
stellar to CMWB energy density would be exactly the same as today,
decreasing as the fourth power of the scale length. But we cannot
turn off stars, and they will continue to add energy in the future.
Thus the ratio of energy densities will increase with time until all
stars have burned out.

> And "what I meant by this" is that we don't discover entirely new
> galaxies where none existed before, say, 10 or 20 years ago. We
> are only able to bring new more-distant ones into focus.

The number of galaxies is thought to be decreasing because of
mergers, but I don't see what this has to do with any of your other
claims. We see new stars forming in many locations, and we certainly
expect existing stars to keep radiating for quite awhile.

> > SW> "Coalescence" into what?
> >>
> >> Proto-galaxies, for a start.
> >
> > How does this keep the Universe from being optically thick?
>
> It doesn't. It presents the inside of an event horizon as an
> optically thick surface *also*.

I guess I don't understand your model. If you have an optically
thick plasma at a redshift of a few thousand, it will be very hard to
observe anything at higher redshift. And if you don't have an
optically thick plasma back then, I think you will have quite some
trouble to explain where all the baryons were.

> No. A "way around it" is that the CMBRM is the inside of the
> event horizon, a temperature TBD, and structures exist right up
> to it.

But where were all the baryons at z=2000? What was their density and
temperature, and why didn't they create a medium that was optically
thick? "Coalescence" is too vague. Exactly what state were these
baryons in? What size objects with what average density? Hand
waving is no good; let's see some numbers.

By the way, I share the standard GR view that an event horizon is not
a physical singularity. And certainly the event horizon is not a
requirement for an accretion disk to exist. After all, neutron star
accretion disks look pretty much the same as black hole accretion
disks, so the disk and its radiation cannot depend on an event
horizon. (If you compare the time variability in great detail, you
can indeed find differences, but the existence and basic structure of
the disks seems to be the same.)

--
Steve Willner Phone 617-495-7123 swillner@xxxxxxxxxxxxxxx
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
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