The problem of spectroscopic determinations of luminosity and parallax has been investigated at Mount Wilson with great thoroughness from all sides, the separate investigations checking each other. A definitive scale for the spectroscopic determination of absolute magnitudes has now been established, and the parallaxes and absolute magnitudes have already been derived for about 1,800 stars. CHAPTER XLIX THE NEAREST STARS Of especial interest are the few stars that we know are the nearest to us, and the following table includes all those whose parallax is 0".20 or greater. There are nineteen in all and nearly half of them are binary systems. The radial motions given are relative to the sun. The transverse velocities are formed by using the measured parallaxes to transform proper motions into linear measures. They are given by Eddington in his "Stellar Movements": Column Key ==================== A) Magnitude B) Parallax in Seconds of Arc C) Proper Motion in Seconds of Arc D) Linear Velocity Km. per sec. E) Radial Velocity Km. per sec. F) Spectral Type G) Luminosity (Sun=1) H) Star Stream ==================================================================== Star's Name | A | B | C | D | E | F | G | H ---------------+-----+------+------+-----+-----+------+-------+----- 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 |{2.0 | I | | | | | | |{0.6 | 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 --------------------------------------------------------------------