ASTRONOMY 601 



Table 755 

 MISCELLANEOUS ASTRONOMICAL DATA 



Tropical (ordinary) year = ] 365.24219879 — 0.0000000614 (t — 1900) {-days. 



Sidereal year = \ 365.25636042 -f 0.0000000011 (t — 1900) ]■ days. 



Anomalistic year = -j 365.25964134 -j- 0.0000000304 (t — 1900) \ days. 



Eclipse year = -j 346.620000 -j- 0.00000036 it — 1900) \ days. 



Synodical (ordinary) months j 29.530588102 — 0.00000000294 (t — 1900) j- days. 

 Sidereal month = { 27.321660890 — 0.00000000252 it — 1900) \ days. 



Sidereal day (ordinary, two successive tran- 

 sits of vernal equinox, might be called equi- 

 noctial day) =86164.09054 mean solar seconds. 



= 23 h. 56 m. 4.09054 mean solar time. 



Two successive transits of same fixed star = 86164.09966 mean solar seconds. 



1930, Julian Period = 6643. 



January 1, 1933, Julian-day number = 2427074. See p. 603. 



Solar parallax = 8.7958" ± 0.002" (Weinberg). 

 8.807 — 0.0027 (Hincks, Eros). 



8.799 (Sampson, Jupiter satellites; Harvard observations). 

 8.80 Paris conference; 8.8032" ± 0.0013.* 

 Lunar parallax = 3422.63" = 57' 2.63" (Newcomb). 



" =7r' = 3422.519" ± 0.009 (De Sitter).* 

 Mean distance earth to sun = 149500000 kilometers = 92900000 miles. 

 Mean distance earth to moon = 60.2678 terrestrial radii. 



= 38441 1 kilometers = 238862 miles. 

 Light traverses mean radius of earth's orbit in 498.7 sec. 

 Velocity of light (mean value) in vacuo, 299796 ± 4 km/sec. (Michelson). 

 Constant of aberration = 20.4874" ± 0.005". 



20.47 Paris conference (work of Doolittle and others 

 indicates value not less than 20.51). 

 Light year = 9.5 X io 13 kilometers = 5.9 X io 1 " miles. 



Parsec, distance star whose parallax is 1 sec. = 31 X io 12 km = 19.2 X io 12 miles. 

 General precession = 50.2564" + 0.000222 (t — 1900)" (Newcomb). 



General precession 50.2486" ± 0.0010 (De Sitter, 1927). 



Planetary precession = \ = 0.1228" ± 0.0012 (De Sitter, 1927). 



Lunar-solar precession =p' = 50.3714" ± 0.0016 (De Sitter, 1927). 



Of this 0.0 1 91", Einstein, orbital motion earth.* 

 True lunar-solar precession = p = 50.3523, sun, moon, earth's attraction.* 

 Obliquity of ecliptic = 23° 27' 8.26" — 0.4684 (t — 1900)" (Newcomb). 



Constant of nutation =9.21" (Paris conference) ; 9.208" ±0.003.* 



Constant in long. = A<p = ( — 17.234" — .oi7"T) sin fiVTackson, 



Constant in obliquity =:Ae= ( + 9.218 + .0009T) cos fi JM. N., 1930. 



Latter has relativity correction ; T centuries from 1900. 

 Gravitation constant = (6.670 ± 0.002) X io" 8 dyne cm 2 g" 2 (Heyl, 1930). 



Eccentricity earth's orbit = c =. 0.01675 104 — 0.0000004180 (t — 1900) — 



0.0000000000126 (t — 1900) 2 . 

 Eccentricity moon's orbit = c 2 = 0.05490056 (Brown). 

 Inclination moon's orbit =7 = 5° 8' 43.5" (Brown). 



Delaunay's 7 = sin £7 =0.04488716 (Brown). 



Lunar inequality of earth = L = 6.454" ; 6.459 ± 0.005.* 

 Parallactic inequality moon =(3 = 124.785" (Brown). 

 Mean sidereal motion ofl _ „ „, g 8 « + 0.001294 (t - 1900)". 

 moon s node in 365.25 daysj J y ° ° ' 



Pole of Milky Way = R. A., 12 h. 48 m. ; Dec, + 27 . See p. 604. 



d (lunar perigee) = + 6.386". 



d (lunar node) = — 5-977" ■ 



* De Sitter, Bull. Astron. Inst., Netherlands, 4, 57, 1927. 

 Smithsonian Tables 



