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RE: starship-design: Stars_within_16_light_years_of_the_Sun



> From lparker@cacaphony.net Mon Jun 23 02:29:40 1997
> 
> Zenon,
> 
> No, it is quite correct.
> 
> Lee Parker
> 
> -----Original Message-----
> From:	Zenon Kulpa [SMTP:zkulpa@zmit1.ippt.gov.pl]
> 
> > From: "L. Parker" <lparker@cacaphony.net>
> >
> > Stars within 16 light years of the Sun							
> > NAME          DISTANCE	SPECTRAL	APPARENT	VISUAL
> > 		  (in parsecs)  TYPE		MAGNITUDE 	MAGNITUDE
> > Sun		    N/A		G2 V		-26.72		4.85
> > Proxima Centauri  1.3	M6 V		11.05		15.49
> > Alpha Centauri A  1.33	G2 V		-0.01		4.37
> > Alpha Centauri B  1.83	K1 V		1.33		5.71
> >
> There is most probably an error - the distance to A and B
> is nearly the same, certainly much less than between any of them
> and Proxima, so there should probably be 1.33 parcecs for both.
> 
> -- Zenon
> 
Sorry, but this MUST be in error.
Your data gives B farther away than A by 0.5 ps, that is 1.6 ly,
and at the same distance as to Barnard.
And both these are certainly not true.

I am also including some data from some other sources for comparison below.
Note also differences concerning spectral types and magnitudes
between the sources.

NAME                 DISTANCE         SPECTRAL     APPARENT     VISUAL	
                     (ps/ly)          TYPE         MAGNITUDE    MAGNITUDE
L. Parker source:
-----------------
Proxima Centauri       1.3            M6 V         11.05        15.49	
Alpha Centauri A       1.33           G2 V         -0.01         4.37	
Alpha Centauri B       1.83           K1 V          1.33         5.71	
Barnard's Star         1.83           M4 V          9.54        13.22	


http://www.essex1.com/people/speer/stars.html:
----------------------------------------------
Proxima Centauri      (1.29)/4.2      M5e          11.3
Alpha Centauri A      (1.32)/4.3      G0             .33
Alpha Centauri B      (1.32)/4.3      K5            1.70
Barnard's Star        (1.83)/5.96     M5            9.5


http://monet.physik.unibas.ch/~schatzer/Alpha-Centauri.html:
------------------------------------------------------------
Proxima Centauri      (1.29)/4.22     M5e 
Alpha Centauri A      (1.33)/4.35     G2 
Alpha Centauri B      (1.33)/4.35     K1 

Separation A/B (current): 23 AU = 0.00001 ps

The units:
----------
AU =   149 598 770 km
ly =  9.4543*10^12 km =  63197.7 AU = 0.3066 ps
ps = 30.8361*10^12 km = 206125.7 AU = 3.2616 ly 

-- Zenon