(PUC-RS -2004)1,000 Mira starsThe first detailed s

(PUC-RS - 2004)

1,000 Mira stars

The first detailed study of variable stars in a galaxy outside our Local Group has turned up more than 1,000 luminous red variables in Centaurus A, a giant elliptical galaxy 13 million light-years away. The variable stars are mostly "Mira type", which means they vary by more than 2.5 magnitudes over periods that range between 100 and 1,000 days.

Mira was the first long-period variable discovered and experiences a 1,500-fold change in ¹brightness over a period of 11 months. Mira is a red giant; nearly all red giants are variable stars. The pulsations in a red giant's luminosity are caused by dramatic fluctuations in the star's temperature and size due to its end-of-life phase.

Detecting the variable stars confirms the existence of intermediate-age stars in the halo of Centaurus A. This provides a window on the stellar contents of giant elliptical galaxies and helps scientists understand how these galaxies form. The relationship between the luminosity and the period in the variable stars' fluctuations also confirms previous distance estimates of Centaurus A.

(by Kelly K. Whitt, Astronomy, October, 2003. p. 28)

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