APPENDIX II 
271 
The observed relative masses, calling the mass of the principal star unity, are: 1 to 1.1, the com¬ 
panion being the more massive. But since the brightness of the two components is nearly the 
same, and the difference in observed relative masses is smaller than the probable error properly 
attaching to that difference, the masses are assumed to be equal. On that basis the following table 
has been prepared, giving quantities which must be added to the catalogue-place to get the place 
of the principal star. Reversing the signs of the table and adding, we derive the predicted place of 
the companion star, at the present time north, preceding. 
Date. 
Aa. 
A 5 . 
Date. 
Aa. 
AS. 
Date. 
Aa. 
AS. 
1754 
s 
+ .146 
// 
-2.32 
1844 
S 
— .012 
// 
- -93 
1888 
s 
+ .082 
// 
-2.49 
1756 
+ .147 
-2.30 
1848 
-.003 
—1.24 
1892 
+ .088 
-2.54 
1758 
+ .148 
— 2.26 
1852 
+ .007 
—1.48 
1896 
+ .094 
-2.56 
1812 
+ .118 
- -78 
1856 
+ .016 
-1.68 
1900 
+ .100 
-2.58 
1816 
+ .110 
— .61 
i860 
+ .026 
-1.86 
1904 
+ .106 
— 2.60 
1820 
+ .100 
- -43 
1864 
+ .036 
— 2.00 
1908 
+ .112 
— 2.61 
1824 
+ .086 
- -24 
1868 
+ .044 
— 2.12 
1912 
+ .Il6 
— 2.61 
1828 
+ .069 
- .04 
1872 
+ -05 2 
— 2.22 
1916 
+ .121 
— 2.60 
1832 
+ .045 
+ .16 
1876 
4- .060 
-2.30 
1920 
+ .126 
- 2-59 
1836 
.000 
+ .21 
1880 
+ .068 
-2.38 
1924 
+ • 13 ° 
-2.58 
1840 
— .020 
- - 5 ° 
1884 
+ .074 
-2.44 
No. 3735. a Centauri. 
The magnitudes are 0^0 and 1^5, and the annual parallax may be taken as o"75. This is one of 
the most interesting stars in the sky on account of its large parallax, o''75, and its comparatively 
rapid orbital motion. In computing the place of the center of gravity, the orbit of Roberts (A.N., 
133, io 5 ) was adopted. This makes the period 81.185 years. The components are so widely 
separated that the observations of either should not be seriously affected in a systematic way by the 
presence of the other. In determining the position of the center of gravity, the two components are 
almost equally available. Following is a summary of results for the mass of the fainter compo¬ 
nent, that of the principal star being assumed as the unit: 
Mass 
Wt. 
Observations of fainter star, R.‘ A., 
0.67 
8 
Deck, 
0.78 
55 
Observations of brighter star, R. A., 
0.89 
14 
Deck, 
0.91 
70 
Adopted mean 
p 
bo 
Cn 
The center of gravity appears to be located at about 0.458 p, from the brighter toward the fainter 
star, — p representing the entire distance. In computing the proper-motion, some of the observa¬ 
tions were corrected for parallax, according to a summary process, assuming the parallax to be ''75. 
The following table gives the quantities which must be added to the Catalogue-prediction for the 
respective dates in order to derive the position of the brighter component. If the numbers of the 
table be multiplied by —1.183 an d added to the positions computed from the Catalogue, we shall 
have the positions of the fainter component for the respective dates. 
Date. 
Aa. 
AS. 
Date. 
Aa. 
AS. 
Date. 
Aa. 
AS. 
1830 
S 
+ .700 
// 
+ 7 - 3 i 
1868 
S 
— .172 
// 
-4.42 
1890 
+ '467 
n 
+ 7-54 
1835 
+ .658 
+ 6.11 
1869 
-.199 
- 4-47 
1895 
+ .596 
+ 8-53 
1840 
+ •592 
+ 4.70 
1870 
-.223 
-4.46 
1900 
+ .671 
+ 8.72 
1845 
+ .498 
+ 3.06 
1872 
-.251 
-4.09 
i 9 °S 
+ .707 
+ 8-37 
1850 
+ .406 
+ .76 
1874 
— .246 
- 3- I 7 
1910 
+ .703 
+ 7.61 
1854 
+ .271 
— .21 
1876 
-.188 
—1.60 
1915 
+ .671 
+ 6.49 
1858 
+ •150 
-1.68 
1878 
-.097 
+ .25 
1920 
+ .612 
+ 5.10 
1862 
1866 
+ .019 
— .112 
- 3-°4 
-4.11 
1880 
1885 
+ .017 
+ .279 
+ 2.12 
+ 5.64 
1925 
+ - 5 2 3 
+ 3 - 5 ° 
