Marina Rejkuba of the European Southern Observatory (ESO) and her colleagues discovered the stars using the ESO Very Large Telescope at the Paranal Observatory in Chile. The team searched two fields in the Centaurus A galaxy--an elliptical galaxy located 13 million light-years away from Earth (see image)--more than 20 times between 1999 and 2002. Specifically, the researchers were hunting for signs of changing brightness among the galaxy's stars. Such shifts occur when a star's temperature and size change dramatically near the end of its life. The images that the astronomers collected displayed 1,504 Mira-variables.
The findings represent the first catalogue of variable stars in Centaurus A, a census that the scientists believe to be 90 percent complete. The two fields studied contain different populations of stars, the researchers report. Additional investigation into the cause of this gradient should provide further clues to how Centaurus A formed and evolved.