632 



Tables 819-821 

 TABLE 819.— Stellar Radiation Measurements (Pettit, Nicholson, 1928) 

 Radiometric magnitude = apparent magnitude of an Ao star which will give same radio- 

 metric deflection. Heat index = visual — radiometric magnitudes. Heat index — color 

 index = zero for Ao star. Water-cell-absorption is fraction of radiation eliminated by water- 

 cell expressed in magnitudes. 



Giants, F5-M0, have greater heat indices than dwarfs of same classes. Red stars deviate from 

 black-body conditions. The radiation received at earth's surface at Mount Wilson from star 

 in zenith of zero radiometric magnitude, 1 7. 1 X io- 12 cal./cm 2 /min. Radiometric magnitude 

 Hefner lamp at 1 meter is —20.00; International candle is 1.11 Hefner unit = —20.11; its 

 heat index is 5.82 mag. (i900°K.). 



(All measures reduced to zenith at Mount Wilson, 2 reflections from fresh silver in tele- 

 scope; rock-salt window over thermocouple.) 



TABLE 820. — Spectrum Classes and Temperatures 



Spectral 

 type 



Bo 



B5 



Ao 



A 5 



Fo 



F5 



gGo . . . . 



gGs 



gKo.... 

 gK 5 .... 



gMo 



gM2 



gM 4 .... 



gM6 



gM8 



Me Max 

 Me Min. 

 dGo.... 



dG5 



dKo . . . . 

 dK 5 .... 

 dMo.... 

 dM2.... 



Observed 



Heat 

 index 



Mag. 



O.05 

 .OI 

 .OO 

 .02 



•15 

 •30 



•47 



•65 

 .90 



i-57 

 1.86 

 2.2 



3-i 



4.2 



5-2 



4.4 



8.9 

 •32 

 •39 

 •55 



1. 10 



1.40 



2.1 



Water-cell 

 absorption 



Mag. 

 0.20 



23 

 26 

 30 

 36 

 41 

 5" 

 60 

 70 



93 



<>i 



3° 

 46 



6 J 



5 

 2 



42 



47 

 54 

 76 

 87 



14 



Temperature 



Heat index 



X 0.555m 



6750 



576o 



5000 



4550 



4020 



3240 



3030 



28lO 



24OO 



2050 



1780 



1990 



5700 

 5350 

 4820 

 3720 

 34OO 

 2870 



X 0.52QM 



7300 

 6l6o 

 5450 

 487O 

 4300 

 3480 

 3250 

 3000 

 259O 

 2200 

 2000 

 2l6o 



6lOO 

 5750 

 5IOO 

 3980 

 3650 

 3060 



Water-cell 

 absorption 



7500 

 6200 

 5450 

 4700 

 4140 

 3750 

 3I30 

 2980 

 2810 



2550 

 2390 

 2250 

 2350 

 1830 

 5350 

 4920 

 4460 

 3550 

 3260 

 2780 



Color 

 index* 



230OO 

 150OO 

 1 1 200 

 8600 

 7400 

 6500 

 5500 

 4700 

 4100 

 3300 

 3050 



6000 

 5600 

 5IOO 

 4400 

 3400 



Ioniza- 

 tion! 



20000 

 I 5000 

 1 0000 

 84OO 

 7500 

 7000 

 5600 

 5000 

 4OOO 

 3000 

 3000 



* Russell, Dugan, and Stewart, Astronomy, 2, 734, 1927. t Payne, Stellar atmospheres, 1925. 

 Note — Hottest known stars 20,000 to 30,000 °K, O type, abs. mag. —4, masses 10-80 suns, (Plaskett). 



TABLE 821. — Visual and Radiometric Magnitudes and Total Radiations 



Smithsonian Tables 



