| Star's Name | Magnitude | Parallax in Seconds of Arc | Proper Motion in Seconds of Arc | Linear Velocity Km. per sec. | Radial Velocity Km. per sec. | Spectral Type | Luminosity (Sun=1) | Star Stream | |||
| Groombridge 34 | 8.2 | 0.28 | 2.85 | 48 | ‥ | Ma | 0.010 | I | |||
| Eta Cassiop | 3.6 | 0.20 | 1.25 | 30 | +10 | F8 | 1.4 | I | |||
| Tau Ceti | 3.6 | 0.33 | 1.93 | 28 | -16 | K | 0.50 | II | |||
| Epsilon Erid | 3.3 | 0.31 | 1.00 | 15 | +16 | K | 0.79 | II | |||
| CZ 5h 243 | 8.3 | 0.32 | 8.70 | 129 | +242 | G-K | 0.007 | II | |||
| Sirius | -1.6 | 0.38 | 1.32 | 16 | -7 | A | 48.0 | II | |||
| Procyon | 0.5 | 0.32 | 1.25 | 19 | -3 | F5 | 9.7 | I ? | |||
| Lal. 21185 | 7.6 | 0.40 | 4.77 | 57 | ‥ | Ma | 0.009 | II | |||
| Lal. 21258 | 8.9 | 0.20 | 4.46 | 106 | ‥ | Ma | 0.011 | I | |||
| OA (N) 11677 | 9.2 | 0.20 | 3.03 | 72 | ‥ | ‥ | 0.008 | I | |||
| Alpha Centauri | 0.3 | 0.76 | 3.66 | 23 | -22 | G,K5 |
| I | |||
| OA (N) 17415 | 9.3 | 0.27 | 1.31 | 23 | ‥ | F | 0.004 | II | |||
| Pos. Med. 2164 | 8.8 | 0.29 | 2.28 | 37 | ‥ | K | 0.006 | I | |||
| Sigma Draco | 4.8 | 0.20 | 1.84 | 43 | +25 | K | 0.5 | II | |||
| Alpha Aquilæ | 0.9 | 0.24 | 0.65 | 13 | -33 | A5 | 12.3 | I | |||
| 61 Cygni | 5.6 | 0.31 | 5.25 | 80 | -39 | K5 | 0.10 | I | |||
| Epsilon Indi | 4.7 | 0.28 | 4.67 | 79 | -62 | K5 | 0.25 | I | |||
| Krüger 60 | 9.2 | 0.26 | 0.92 | 17 | ‥ | ‥ | 0.005 | II | |||
| Lacaille 9352 | 7.4 | 0.29 | 7.02 | 115 | +12 | Ma | 0.019 | I | |||
These stars are distant less than five parsecs (about 16 light-years) from the sun, so they make up the closest fringe of the stellar universe immediately surrounding our system. The large number of binary systems is quite remarkable. Why some stars are single and others double is not yet known. By the spectroscopic method the proportion is not so large; Campbell finding that about one quarter of 1,600 stars examined are spectroscopic binaries, and Frost two-fifths to a half. The exceptional number of large velocities is very remarkable; the average transverse motion of the nineteen stars is fifty kilometers per second, whereas thirty is about what would have been expected.
As to star streams to which these nearest stars belong, eleven are in Stream I and eight in Stream II, in close accord with the ratio 3:2 given by the 6,000 stars of Boss's catalogue. "We are not able," says Eddington, "to detect any significant difference between the luminosities, spectra, or speeds of the stars constituting the two streams. The thorough interpenetration of the two star streams is well illustrated, since we find even in this small volume of space that members of both streams are mingled together in just about the average proportion."
The Ring Nebula in Lyra. This is the best example of the annular and elliptic nebulæ, which are not very abundant. (Photo, Mt. Wilson Solar Observatory.)
The Dumb-bell Nebula of Vulpecula. To take the photograph required an exposure of five hours. (Photo, Mt. Wilson Solar Observatory.)