The Red Shift Of Solar Lines And Relativity

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES Volume 12 FEBRUARY 15, 1926 Number 2 THE RED SHIFT OF SOLAR LINES AND RELA TI VITY By CHARLES E. ST. JOHN MOUNT WILSON OBSERVATORY OF THE CARNEGIE INSTITUTION OP WASHINGTON Read before the Academy, April 24, 1924 The differences in wave-length between the center of -the sun's disk and the vacuum arc for 331 iron lines have been used as the basis of a discussion of the displacements of the solar lines in relation to the theory of relativity. In favor of relativity is the general displacement to the red, and against it, certain discordances between the observed and theoretical values. The third and seventh columns of table 1 illustrate what has long been recognized, namely, that both strong and weak lines give displacements at the center of the disk which differ systematically from the calculated values, while lines of medium intensity show displacements in substantial agreement with the theoretical requirement. The observed displacements of strong lines are about 50 per cent greater, and of weak lines about 30 per cent less than the predicted results. This discrepancy has long stood in the way of an interpretation based upon general relativity. It is the purpose of the present discussion to suggest a harmonizing interpretation. TABLE I COMPAUISON OF OBSERVED DIsPLAcEmuNTs (SUN minus VAcuuIM) wiTH THosE CASE CULATED FROM THE THEORY or RELATMITY NO. Or GROUP LINNS a 17 b b 24 10 10 131 106 33 a b d a MRAN SOLAR WAVEINTENSITY LENGTH 12 14 10.4 6.2 4.8 4.5 3.3 3826 A 3821 4308 5443 4758 4763 4957 RADIAL CALCULATED OBSERVED OBS.-CAL. VELOCITY 0.008 A 0.012 A +0.004 A 0.3 km./sec. down 0.008 0.0112 +0.0032 0.25 km./sec. down 0.0091 0.0113 +0.0022 0.16 km./sec. down 0.0115 0.0100 0.0100 0.0105 0.0112 0.0084 0.0069 0.0074 -0.0003 -0.0016 -0.0031 -0.0031 .............. 0.1 km./sec. up 0.2 km./sec. up 0.2 km./sec. up The key to the solution offered is that the deviations from theory shown by the strong and weak lines are correlated primarily, not with lineintensity, but with the level in the sun's atmosphere at which the lines ASTRONOMY: C. E. ST. JOHN 66 PROC. N. A. S. are produced. This is clearly evident from the behavior of lines of enhanced and normal titanium as shown in table 2. Lines in the flash spectra at heights of 6000, 1300 and 435 km. show absolute displacements of +0.015, +0.0112 and 0.0054 A, respectively, and deviations of +0.007, +0.002 and -0.0034 A from the displacements calculated according to the relativity theory, a definite correlation with level. That the deviations are not fundamentally associated with line-intensity is shown by comparing the last two groups, consisting of enhanced and normal lines of approximately equal intensities, which show absolute displacements of +0.0112 and +0.0054 A, and deviations of +0.002 and -0.0054, respectively, from the calculated values. TABLE 2 RJW-DISPLACamsNT AND LsvEL Enh. Ti Enh. Ti Normal Ti NO. MEAN INT. 2 11 4.6 4.2 8 5 SUN-VAC. +0.015 A +0.0112 +0.0054 OBS.-CAL. +0.007 A +0.002 -0.0034 HEIGHT 6000 km. 1300 435 The systematically larger displacement of high-level lines toward the red which appears clearly in table 1, has also been observed on highdispersion spectrograms of Sirius, Procyon and Arcturus, and, in general, is the more pronounced the higher the temperature of the star. In attempting to interpret the observed displacements, it is to be remarked that the low pressure now known to exist in the reversing layer of the sun, and confirmed b