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The relationship is represented by the equation: = where L ⊙ and M ⊙ are the luminosity and mass of the Sun and 1 < a < 6. [2] The value a = 3.5 is commonly used for main-sequence stars. [ 3 ] This equation and the usual value of a = 3.5 only applies to main-sequence stars with masses 2 M ⊙ < M < 55 M ⊙ and does not apply to red giants ...
Mass-to-light ratios in application can be used to gain insight into the dark matter content and dust extinction in a galaxy. [4] Historically, rotation curves for spiral galaxies have been used to study galaxies, but mass-to-light ratios prove more accurate as a method of measuring mass. [5]
The Tully–Fisher relation for spiral and lenticular galaxies. In astronomy, the Tully–Fisher relation (TFR) is a widely verified empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. Since the observed brightness of a galaxy is distance-dependent, the ...
Henrietta Swan Leavitt (/ ˈ l ɛ v ɪ t /; July 4, 1868 – December 12, 1921) was an American astronomer. [2] [1] [3] Her discovery of how to effectively measure vast distances to remote galaxies led to a shift in the scale and understanding of the scale and the nature of the universe. [4]
A preliminary description of the three areas of this diagram was made in 2003 by Eric F. Bell et al. from the COMBO-17 survey [1] that clarified the bimodal distribution of red and blue galaxies as seen in the analysis of Sloan Digital Sky Survey data [2] and even in de Vaucouleurs's 1961 analyses of galaxy morphology. [3]
Therefore, the stellar luminosity function is used to derive a mass function (a present-day mass function, PDMF) by applying mass–luminosity relation. [2] The luminosity function requires accurate determination of distances, and the most straightforward way is by measuring stellar parallax within 20 parsecs from the earth.
The observational result of Hubble's law, the proportional relationship between distance and the speed with which a galaxy is moving away from us, usually referred to as redshift, is a product of the cosmic distance ladder. Edwin Hubble observed that fainter galaxies are more redshifted. Finding the value of the Hubble constant was the result ...
The choice of using 50% was arbitrary, but proved to be useful in further works by R. A. Fish in 1963, [147] where he established a luminosity concentration law that relates the brightnesses of elliptical galaxies and their respective R e, and by José Luis Sérsic in 1968 [148] that defined a mass-radius relation in galaxies. [139]