Page:Popular Science Monthly Volume 12.djvu/59

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49
THE SYSTEM OF SIRIUS.

remarked that this brilliant star is slowly moving in space, like all the other stars, but that its proper movement is not uniform; and Bessel announced, thirty years ago, that at some time there would be discovered, without doubt, a world of its system moving around it and disturbing it in its progress. This discovery was made in 1862. The companion of Sirius was then almost exactly on the eastern side, quite small, and buried in the rays of the star. Since that year it has been constantly watched by the aid of powerful instruments, and it is seen to slowly gravitate around the Sirian sun.

But this companion certainly does not follow the theoretic orbit calculated to correspond to the perturbations noted in the proper movement of the brilliant star. Differences more and more marked are shown between the calculated ellipse and the observed ellipse. The following is the orbit calculated by the German astronomer Auwers in 1864 to correspond with recognized perturbations:

Passage by lower apsis 1793.890
Annual movement 70.28475
Period years 49.418
Eccentricity 0.6010

The last orbit calculated by Auwers, placed in the form of the orbits of double stars, and given as definitive, is the following:

Perihelion passage 1843.275
Longitude of node 61°.57,8
Angle between node and perihelion 18°.54,5
Inclination 47°.8,7
Eccentricity 0.6148
Semi-major axis 7".331
Period years 49.399
 

From these elements, the limits of distance ought to be 2.31" at 302.5° in 1841, and 11.23" at 71.7° in 1770, and the ephemeris is—

 
           
1862 85°.4 10".10 1874 65°.0 10".95
1865 79°.9 10".78 1876 62°.1 10".59
1868 75°.0 11".15 1878 58°.4 10".05
1871 70°.3 11".20 1880 54°.2 9".33
           
 

But, in making out my "Catalogue of Double Stars in Movement," I have found that all the observations on the satellite of Sirius give the following means for each year since its discovery:

 
           
1862 84°.6 10".08 1870 65°.0 12".06
1863 82°.2 9".84 1871 63°.0 11".79
1864 79°.0 10".33 1872 61°.3 11".34
1865 76°.7 10".56 1873 62°.7 11".33
1866 75°.0 10".61 1874 58°.5 11".18
1867 73°.9 10".39 1875 55°.5 11".30
1868 70°.4 11".18 1876 55°.2 11".51
1869 72°.3 10".92 1877 51°.0 11".40