Re: ASTRONOMY: Dark Matter & White Dwarfs

From: Robert J. Bradbury (
Date: Sat Mar 24 2001 - 04:34:53 MST

I said:
> >What is interesting about this is that it seems when the
> >astronomers see something they don't expect, they go back
> >and check the instruments... :-) I wonder if the SIs think
> >of the astronomers as rats running a maze trying to find the
> >cheese...

On Sat, 24 Mar 2001 responded:
> Hey, that's a very logical response. Really, instruments do goof a lot.

True, but I can just picture the astronomers going, "When we
look at all these stars the instrument is fine, but when we
look at this one star the instrument gets flakey...".

> >Now personally, I cannot imagine any artificial structures that
> >would match the spectra of these two objects.
> What's the predicted spectrum of a semi-Dysonized star?

I've thought a fair amount about that (since part of my talks
at the OSETI III conference were about suggesting that scientists
look at Long-Period Variable Stars) and it isn't clear.

Imagine building out the Dyson sphere from an orbiting planet.
Presumably you begin to send your satellites out ahead of and
behind the planet in orbit. Or perhaps send them sunward
or anti-sunward (depending on the planet's orbit). You probably
want to do this in a fashion that requires a slowly increasing
Delta-V (as you slowly get more energy to throw at the problem).

Spike worked out an approach where you could do this using photon
pressure alone but I think it takes a *long* time. He or Doug
might want to comment on how you could do it for the lowest cost
if you had material you didn't mind throwing away (after all you
will be collecting large amounts of mass from the solar wind).

Now bear in mind that these orbits are going to periodically
obscure the star as they pass between the star and the earth
along our line of sight. So the visible and IR power output
of the star are going to undergo wierd oscillations. Depending
on orbits of the planets from which these are being constructed
these oscillations may range from days to years. Then there
will be a long period shift as more and more of the energy
output gets moved from visible into the IR (effectively making
the star "cooler"). So we would have to observe these stars
periodically to see what is happening to their light output.


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