At 12:27 PM 6/9/01, Alberto Monteiro wrote:
>Ronn Blankenship wrote:
> >
> > From which well-known Sun-like star do the other well-known
> > stars Sirius, Procyon, and Epsilon Eridani all appear against
> > the background of a slightly distorted Leo, the Lion?
> >
>2nd approximation: I computed the "mean" position of
>those 3 stars, the "mean" position of the stars of Leo,
>and got:
>
>Mean of Sirius, Procyon, and Epsilon Eridani is
>a point at RA = 5.971184 h, Dec = -6.755817 deg, r = 2.758257 pc
>(S, P and E are, respectively, 0.702685 pc, 1.646586 pc, and
>1.957545 pc from this mean point)
>
>Mean of Leo is RA = 11.089920 h, Dec = 18.821237 deg
>
>Then, I checked all stars I have in a database here for
>those that would see S, P & E at most 15 deg from the
>mean of Leo. Unfortunately, I got a too-long list, with
>too-many stars, and none of them seem to be a "well-known
>Sun-like star".
>
>The best fit to that might be Beta Cetus,
>also known as Diphda, a K1 star at RA = 0.72 hours,
>dec = -17.98 deg, dist = 18 parsecs - with an
>extra advantage, that Sol would be 22 deg from the
>mean of Leo.
It's a K1 III (giant), though, which probably disqualifies it as a
"Sun-like" star.
At 04:19 PM 6/9/01, Alberto Monteiro wrote:
>Ronn Blankenship wrote:
> > [the same thing as above ;-) ]
>
>3rd approximation: Tau Ceti - but Epsilon Eridani,
>relative to Tau Ceti, would be ~30 deg from the "mean"
>position of Leo.
This is the answer I had in mind. I'll grant that future astronauts from
Earth observing from a hypothetical planet of Tau Ceti might be more likely
to assign Eps Eri to Cancer than to Leo (assuming they didn't go ahead and
redraw everything from scratch). As a G8 V star, Tau Ceti is more Sun-like
than Diphda, although I recall that the explorers in Heinlein's juvie _Time
for the Stars_ discovered suitably Earth-like planets orbiting both.
From Tau Ceti, Sol appears about 5 degrees from (and about two magnitudes
fainter than) Arcturus (which is about half a magnitude fainter than it is
from Earth), something I don't remember Heinlein mentioning in the scene
where his protagonist is trying to locate Sol in the sky of Tau Ceti. Of
course, it has been a number of years since I read that book . . .
For the easy way to get an answer to this and similar problems, go to
<http://www.shatters.net/celestia/> and download the free program Celestia,
which allows you to view the sky from anywhere in the solar system or any
of the visible stars (it even includes a number of the known extrasolar
planetary systems). I actually first noticed the alignment I mentioned
while using another (non-free) program which reported the three stars as
all being in the constellation of Leo, probably based on transformation of
the coordinates of the IAU constellation boundaries, which the current
version of Celestia doesn't appear to have any way of showing. (The
current version does not come with a help file, though it's pretty easy to
use.)
-- Ronn! :)
