Re: PHYS: dyson shell thermodynamics

Amara Graps (
Mon, 27 Oct 1997 08:50:30 -0800

>On Fri, Oct 24, 1997 at 10:36:03PM -0800, Amara Graps wrote:
>> For example, the four brightest infrared excess stars are
>> alpha Lyr, alpha PsA, beta Pic, and eps Eri. Those four have
>> dust temperatures (micron-sized dust around the star) of 85K, 60K, 110K, and
>> 50K, respectively.
>> So I don't think that something like this would be invisible to
>> our current instrumentation.
>Interesting. Would these stars have been found if their spectra didn't
>also have higher frequency components?

"Higher frequency" ? I didn't mention anything about higher frequency.
(Higher frequency of what?, I should probably ask)

Maybe you are thinking about the Doppler velocity techniques that
astronomers have used to discover Jupiter-sized planets around
other (main sequence) stars. If so, that is completely different.
I was talking about infrared excess stars. The physics involved
with the IR excess stars is about energy and fluxes and heat. See the URL
I gave previously ( for
some notes about that.

The Doppler velocity techniques are all about.. well doppler velocities.
The techniques are similar to those used in helioseismology.

Geoff Marcy's URL has some words about his planet finding
techniques here:

and I wrote a detailed explanation about helioseismology for
my Stanford job (solar oscillations group) here:

Actually I have thought alot about calculating if the stars in
Marcy et al's (Doppler) speculated planet systems also have IR excesses
(I even discussed it with him a couple of years ago), but I have
not done the calculations yet. It would be an interesting result
(maybe someone has already done it by now).

These stars that we are talking about, both the IR excess stars and
and the Doppler velocity stars are all nearby: 25 parsecs or less.

>If we're to spend say 1 to 10
>million dollars with best current technology on a dyson sphere search,
>what is the radius in which we'd have a good chance of finding one if it

You would absolutely have to have a database of stars with parallaxes.
I don't know what is the Hiparccos catalog's radius for stars. If
your search for Dyson spheres uses the Wooley or Gliese catalogs
to provide parallaxes, (those are the catalogs used by Fred Witteborn,
my old boss at NASA-Ames, when he searched for Dyson spheres in the
early 80's) then that radius would be 25 parsecs or less.

There are lists around of candidate search stars for finding
other planets. Geoff Marcy's group has one. The Terrestrial
Planet Finder working group will have one soon. The Kepler and
Darwin missions already have lists for candidate stars. Project
Phoenix (SETI) has a list of candidate stars, as well. I don't know
how much overlap there is, but I would be that there is a huge
overlap of stars in those lists. I believe that alot of this information
is available at these different groups' Web sites.

This place is an excellent place to start learning about the
status of finding other solar systems:


Amara Graps email:
Computational Physics vita: finger
Multiplex Answers URL:
"Drosam pieder pasaule." (The world belongs to the brave.)
--a Latvian proverb