Gore — A Catalogue of Binary Stars, 8fc. 
585 
28. a Centauri. This well-known binary is also the nearest of all 
the fixed stars to the earth, as far as is known at present. Although 
carefully measured for many years, its orbit is still somewhat doubtful. 
While Downing and Elkin make the period 76 or 77 years, Powell 
maintains that a longer period of about 87 years is more probable 
{Mon. Notices^ IN'ov., ] 884). A few years more should decide the ques- 
tion. Downing' s elements combined with Gill's parallax of 0"-76 gives 
a mass of 2*0406 that of the sun. Some recent measures are : — 
1884-194 : 199°-0 : ll"-96, Eussell. 
1884-433 : 199 -5 : 12 -32, ,, 
From measures of Aa and AS. 
E. of Meridian. 
1885-527 
1885-571 
1885-582 
1885-590 
198°-6 
199 -8 
200 -8 
201 -1 
13"-47. 
14 -40. 
14 -08. 
W. of Meridian. 
201°-7 : 14"-03, Tebbutt. 
202 -0 : 14 -17, „ 
201 -2 : 14 -17, „ 
201 -2 : — 
1886-449 
1886-487 
1886-548 
200°-80 
202 -46 
201 -02 
14"-97, Eussell. 
15 -05, Pollock. 
14-87, „ 
Prom measures of Aa and AS. 
29. ^Bootis = 5 1888. A double star, discovered by Sir W. Herschel, 
April 9, 1780; but he did not measure the position angle till 1782, 
when he found it about 24° (as now reckoned). Since that year the 
companion has described about 1 30° of the apparent orbit. Dr. Doberck's 
orbit is probably the best. Some recent measures are : — 
1881-245 
: 274°-85 
: 4"-03, Doberck. 
1882-33 
272 
•13 
4 
•03, „ 
1884-45 
266 
-6 
3 
-65, Engelmann. 
1885-366 
264 
•29 
: 3 
•44, Tarrant {A. N., 2866). 
1885-55 
: 263 
•1 
. 3 
•61, Engelmann. 
1886-60 
. 259 
•4 
3 
•32, 
1887-50 
257 
•0 : 
3 
•01, Schiaparelli. 
1888-621 
253 
•87 
3 
•52, Maw. 
Observatory, March, 1889). 
30. 44 (i) Bootis = ^ 1909. Doberck's orbit is probably the best. 
As the inclination of the orbit plane is high, the position angle 
