CHAPTER III.
SOME GROUPS OF KNOWN STARS.
29.
The number of cases in which all the eight attributes of the stars discussed in the first chapter are well known for one star is very small, and certainly does not exceed one hundred. These cases refer principally to such stars as are characterized either by great brilliancy or by a great proper motion. The principal reason why these stars are better known than others is that they lie rather near our solar system. Before passing on to consider the stars from more general statistical points of view, it may therefore be of interest first to make ourselves familiar with these well-known stars, strongly emphasizing, however, the exceptional character of these stars, and carefully avoiding any generalization from the attributes we shall here find.
30.
The apparently brightest stars. We begin with these objects so well known to every lover of the stellar sky. The following table contains all stars the apparent visual magnitude of which is brighter than 1m.5.
The first column gives the current number, the second the name, the third the equatorial designation (αδ). It should be remembered that the first four figures give the hour and minutes in right ascension, the last two the declination, italics showing negative declination. The fourth column gives the galactic square, the fifth and sixth columns the galactic longitude and latitude. The seventh and eighth columns give the annual parallax and the corresponding distance expressed in siriometers. The ninth column gives the proper motion (μ), the tenth the radial velocity W expressed in sir./st. (To get km./sec. we may multiply by 4.7375). The eleventh column gives the apparent visual magnitude, the twelfth column the absolute magnitude (M), computed from m with the help of r. The 13th column gives the type of spectrum (Sp), and the last column the photographic magnitude (m′). The difference between m′ and m gives the colour-index (c).
TABLE 2.
THE APPARENTLY BRIGHTEST STARS.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 |
| Name | Position | Distance | Motion | Magnitude | Spectrum | ||||||||
| (αδ) | Square | l | b | π | r | μ | W | m | M | Sp | m′ | ||
| sir. | sir./st. | m′ | |||||||||||
| 1 | Sirius | (064016) | GD7 | 195° | - 8° | 0″.876 | 0.5 | 1″.32 | - 1.56 | -1m.58 | -0m.3 | A | -1.58 |
| 2 | Canopus | (062152) | GD8 | 229 | -24 | 0.007 | 29.5 | 0.02 | + 4.39 | -0.86 | -8.2 | F | -0.40 |
| 3 | Vega | (183338) | GC2 | 30 | +17 | 0.094 | 2.2 | 0.35 | - 2.91 | 0.14 | -1.6 | A | 0.14 |
| 4 | Capella | (050945) | GC5 | 131 | + 5 | 0.066 | 3.1 | 0.44 | + 6.38 | 0.21 | -2.8 | G | 1.13 |
| 5 | Arcturus | (141119) | GA2 | 344 | +68 | 0.075 | 2.7 | 2.28 | - 0.82 | 0.24 | -1.9 | K | 1.62 |
| 6 | α Centauri | (143260) | GD10 | 284 | - 2 | 0.759 | 0.3 | 3.68 | - 4.69 | 0.33 | +3.2 | G | 1.25 |
| 7 | Rigel | (050908) | GD6 | 176 | -24 | 0.007 | 29.5 | 0.00 | + 4.77 | 0.34 | -7.0 | B8p | 0.25 |
| 8 | Procyon | (073405) | GC7 | 182 | +14 | 0.324 | 0.6 | 1.24 | - 0.74 | 0.48 | +1.5 | F5 | 1.17 |
| 9 | Achernar | (013457) | GE8 | 256 | -59 | 0.051 | 4.0 | 0.09 | .. | 0.60 | -2.4 | B5 | 0.87 |
| 10 | β Centauri | (135659) | GC10 | 280 | + 2 | 0.037 | 5.6 | 0.04 | + 2.53 | 0.86 | -2.9 | B1 | 0.45 |
| 11 | Altair | (194508) | GD1 | 15 | -10 | 0.238 | 0.9 | 0.66 | - 6.97 | 0.89 | +1.2 | A5 | 1.12 |
| 12 | Betelgeuze | (054907) | GD6 | 168 | - 8 | 0.030 | 6.9 | 0.03 | + 4.43 | 0.92 | -3.3 | Ma | 2.76 |
| 13 | Aldebaran | (043016) | GD5 | 149 | -19 | 0.078 | 2.8 | 0.20 | +11.63 | 1.06 | -1.2 | K5 | 2.67 |
| 14 | Pollux | (073928) | GC6 | 160 | +25 | 0.064 | 3.2 | 0.07 | + 0.82 | 1.21 | -1.3 | K | 2.59 |
| 15 | Spica | (131910) | GB8 | 286 | +51 | .. | .. | 0.06 | + 0.34 | 1.21 | .. | B2 | 0.84 |
| 16 | Antares | (162326) | GC11 | 320 | +14 | 0.029 | 7.1 | 0.03 | - 0.63 | 1.22 | -3.0 | Map | 3.06 |
| 17 | Fomalhaut | (225230) | GE10 | 348 | -66 | 0.138 | 1.5 | 0.37 | + 1.41 | 1.29 | +0.4 | A3 | 1.43 |
| 18 | Deneb | (203844) | GC2 | 51 | + 1 | .. | .. | 0.00 | - 0.84 | 1.33 | .. | A2 | 1.42 |
| 19 | Regulus | (100312) | GB6 | 196 | +50 | 0.033 | 6.3 | 0.25 | .. | 1.34 | -2.7 | B8 | 1.25 |
| 20 | β Crucis | (124159) | GC10 | 270 | + 3 | 0.008 | 25.8 | 0.06 | + 2.74 | 1.50 | -5.6 | B1 | 1.09 |
| sir. | m′ | ||||||||||||
| Mean... | .. | .. | .. | 23°.5 | 0″.134 | 7.3 | 0″.56 | 3.26 | +0m.64 | -2m.1 | F1 | +1.13 | |
The values of (αδ), m, Sp are taken from H. 50. The values of l, b are computed from (αδ) with the help of tables in preparation at the Lund Observatory, or from the original to [plate I] at the end, allowing the conversion of the equatorial coordinates into galactic ones. The values of π are generally taken from the table of Kapteyn and Weersma mentioned in the previous chapter. The values of μ are obtained from B. P. C., those of the radial velocity (W) from the card catalogue in Lund already described.