Wilson–Bappu effect

The Wilson - BAPPU effect is a physical- astronomical effect that is used to determine the distance of stars.

In 1957, Olin C. Wilson and MK Vainu BAPPU reported the remarkable correlation between the width of the emission line at the center of Ca II K and the absolute brightness of a star. This effect is called Wilson BAPPU effect. The effect is independent of the spectral type of the star and are valid for spectral types G, K and M.

This method is to determine one of many ways to extragalactic distances. Once you know the absolute magnitudes, one can by means of the formula

Determine the distance. Although in theory this method has the possibility of up to a distance to carry out reliable distance calculations for stars of 7 Megaparsek, it is generally used only for stars with a distance of up to several hundred Kiloparseks. It is also important that this is only for stars with a brightness of greater than 15 may work.

Swell

• Wilson, OC and MK Vainu BAPPU: H and K Emission in Late -Type Stars: Dependence of Line Width on Luminosity and Related Topics. In: Astrophysical Journal, Volume 125, 1957, pp. 661-683.

• Observational astronomy