770 



TABLE 881. 



-PROPERTIES AND CLASSIFICATION OF STAR CLUSTERS 



(concluded) 



Part 2. — Galactic star clusters 



Columns 2 through 6 from Shapley. 208 Distances from R. J. Trumpler, unpublished. 

 Linear diameters computed on basis of revised distances. 1 kiloparsec = 3lXl0 ls km = 

 3X10 3 light-years. 



NGC RA (1900) Dec 



h m 



663 1 39.2 +60°44' 



869 2 12 +56 41 



884 2 15.4 +56 39 



Pleiades ... 3 41 +23 48 



Hyades .... 4 14 +15 23 



1960 5 29.5 +34 04 



2099 5 45.8 +32 31 



2632 8 34.3 +20 20 



Mel in .... 12 20 +26 40 



6705 18 45.7 — 6 23 



7654 23 19.8 +61 03 



2U3 Star clusters, p. 228, McGraw-Hill, 



TABLE 882.— OUR GALAXY, ITS CENTER AND ROTATION* 



The center of the galaxy apparently lies among the dense Milky Way clouds in Sagittarius, at 

 a distance of about 9,000 to 10,000 parsecs from the sun. About this center the sun revolves with 

 a period of some 200 million years at an orbital speed of nearly 300 km/sec. The amount of 

 matter within the sun's orbit is probably more than 200 billion times the sun's mass. In the 

 table, A is the differential orbital radial velocity per kiloparsec of distance from the sun, rA is 

 the maximum group velocity for a distance r, and L is the longitude of the galactic center. The 

 sun is about 33 parsecs above the galactic plane. 2 " 4 



Stars No. 



O-M 210 



0-B7 849 



Interstellar 261 



B-K 3786 



P G C and 18 C .... 4233 



K 392 



Plan '"Neb ....Y.I.... HO 



Cepheids 156 



O B, Ceph, c, gas 



c 205 



5-B5 987 



Irreg var 116 



Vis 

 mag 

 limit 



8.0 

 7.5 

 8.6 



7.5 



14.1 



8.4 

 6.4 



Distance 

 kpc 



.2- 1.1 

 .2- 1.4 

 .4- 1.2 



.2 

 .5-12.0 

 .4— 2.3 

 .2-10.0 

 .2- 1.3 

 .3- 1.1 



.5 



Max 



r A 

 km /sec 



35 



22.2 



13.5 



264 

 39.4 

 39.6 

 26.6 

 18.8 

 9.5 



A 

 km sec 1 kpc - 



19.0 

 15.0 

 16.6 

 15.0 

 15.0 

 17.0 

 14.0 

 20.9 

 17.7 



324 

 324.4 

 331.7 

 324 



17 ' 



333.0 

 325.3 

 326.0 

 324.4 



325.7 



Dist 



to 



center 



kpc 



6.3 

 10.0 



6.5 



9.4 



10.0 



9.4 



Source 28S 



a 

 b 

 c 

 d 

 e 

 f 



g 

 h 

 i 



J 

 k 



1 



* Prepared by A. H. Joy, Mount Wilson Observatory. 



294 Gerasimic, Luyten, Proc. Nat. Acad. Sci., vol. 13, p. 180, 1927. 



2 " r> a, Oort, Bull. Astron. Inst. Netherlands, vol. 4, p. 80, 1927. b, Plaskett, Pearce, Publ. Dominion 



Astrophys. Obs.. vol. 5, p. 241, 1936. r, Plaskett, Pearce, Publ. Dominion Astrophys. Obs., vol. 5, p. 167, 



1933. d, Lindblad, Monthly Notices, Roy. Astron. Soc, vol. 90, p. 503, 1930. e, Wilson, R., Astron. 



Tourn., vol. 40, p. 121, 1930. f, Redman, Publ. Dominion Astrophys. Obs., vol. 6, p. 27, 1931. g, Berman, 



Lick Obs. Bull., vol. 18, p. 57, 1937. h, Jov. Astrophys. Journ., vol. 89, p. 356, 1939. i, Wilson, 



Astrophys. Journ., vol. 93, p. 212, 1941. k, Wilson, Astrophys. Journ., vol. 94, p. 12, 1941. 1, Wilson, 



Astrophys. Journ., vol. 96, p. 371, 1942. 



SMITHSONIAN PHYSICAL TABLES 



