(SNES) Are the Stars Fading?

[Albireo54@aol.com]

Hi Gang,

During a recent night at FDO the subject of Sirius' brightness came up (it 
often does with the public) and someone ......I think it was 
Les......mentioned a
value of -1.09. Most of us had a figure of -1.41 or -1.46 in mind. Well, the 
long established values are in the -1.4 to -1.5 range. However, the new Tycho 
2 catalog (issued early last year), based on the detailed observations of the 
Hipparchos satellite, have revised the visual magnitudes of millions of 
stars, as well as improving their position, proper motion, and spectral 
measurements. Sirius does indeed now come in at -1.09, a reduction of some 
40% in brightness - good going Les! But don't worry.....Sirius is still 
easily the brightest star in the heavens. The next one, Canopus (-0.63) is 
never visible from New England, but lovely Vega (0.09) has now moved into 
third position overall.

On average, visual magnitudes seem to have been reduced by some 15% - not 
especially noticeable. A list of changes down to the star Regulus appears 
below (sorry for the unavoidable formatting glitches.) One of the most 
interesting results of the Hipparchos measurements confirms a long held 
suspicion - that Alpha Cygni (Deneb) is probably the most brilliant star we 
know of in our galaxy. Its accepted distance is now 3,229 light years. If 
that is correct, its absolute magnitude exceeds -8, and it is at least 
230,000 times brighter than the sun - if not more!

BRIGHTEST STARS - with Revised Tycho 2 Values

Desig.     Con  Name                  RA         Dec         Mag   Dist     
New Mag
------------------------------------------------------------------------------

-------
Alpha A    CMa  Sirius                06h 45.1m  -16d 42'    -1.46     9        
-1.09
Alpha      Car  Canopus               06h 23.8m  -52d 41'   -0.72    74     
-0.63
Alpha      Boo  Arcturus              14h 15.6m  +19d 12'   -0.04    34  0.14
Alpha A    Cen  Rigil Kentaurus    14h 39.5m  -60d 49'   -0.01     4          
 0.16
Alpha      Lyr  Vega                    18h 36.8m  +38d 46'    0.03    25    
0.09
Alpha AB   Aur  Capella               05h 16.4m  +45d 59'   0.08    43   0.24
Beta A     Ori  Rigel                    05h 14.7m  -08d 13'    0.12  1400   
0.28
Alpha A    CMi  Procyon               07h 39.2m  +05d 14'    0.38    11     
0.46
Alpha      Eri  Achernar              01h 37.5m  -57d 15'    0.46    69      
0.53
Alpha      Ori  Betelgeuse            05h 55.0m  +07d 24'    0.50  1400  0.58 
(v)
Beta AB    Cen  Hadar                 14h 03.6m  -60d 21'    0.60   320  0.58 
(v)
Alpha AB   Cru  Acrux                 12h 26.4m  -63d 04'    0.76   510  0.70
Alpha      Aql  Altair                19h 50.7m  +08d 51'    0.77    16      
0.93
Alpha A    Tau  Aldebaran             04h 35.7m  +16d 30'    0.85    60  1.00 
(v)
Alpha A    Sco  Antares               16h 29.3m  -26d 26'    0.90   522  1.09 
(v)
Alpha      Vir  Spica                 13h 25.0m  -11d 08'    1.00   220      
1.04 (v)
Beta       Gem  Pollux                07h 45.2m  +28d 02'    1.14    35      
1.22
Alpha      PsA  Fomalhaut             22h 57.5m  -29d 39'    1.16    22  1.23
Beta       Cru  Becrux                12h 47.6m  -59d 40'    1.20   460      
1.30 (v)    
Alpha      Cyg  Deneb                 20h 41.3m  +45d 16'    1.25  1500  1.33
Alpha A    Leo  Regulus               10h 08.2m  +12d 00'    1.35    69  1.40

Enjoy them still!
:o)
Doug Stewart
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