FreeLists / az-observing / [AZ-Observing] Re: Kappa Gemini

["Steve Coe" <stevecoe@xxxxxxxxx>]

Brian;

I suspected as much, since many of the colors of star pairs are a =
contrast
effect.  This would certainly be an interesting study; which of the =
"famous"
stars with color are actually somewhat near the color as given by the
spectra of that star.  I have no doubt that this is the type of thing =
that
would never get a grant to study, but it certainly would be fun to do.

Clear skies to us all;
Steve Coe


-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Brian Skiff
Sent: Tuesday, April 11, 2006 9:25 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Kappa Gemini

>>  ...colors of the two stars as light yellow and AQUA--honest!!
>>  ...I don't have the actual spectrum, but I will try and find it.

     I'm not absolutely sure, but I think there is no spectral type
available for the companion.  However, kappa Gem is G8III (G8 giant),
in fact a standard of this spectral type.  The companion is shown in
several places as being between 5.5 and 6 magnitudes fainter than=20
the primary.  This means it must be an early-K dwarf, and thus =20
actually has almost identical B-V color as the giant.  So the color
difference you see is essentially entirely physiological, and with
the large brightness-difference, the pale-blue color of the fainter
star is exactly what you expect, in the sense that this is the common
impression.  Very convincing, and I've seen it on hundreds of pairs,
but it exists only inside your head.

\Brian
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