1. What is the Andromeda Galaxy? The nearest galaxy from our Milky Way. 2.3M light year away. Considered that it has structure similar to our Milky Way. ↓ Investigation of the Andromeda Galaxy will enable us to know about our Milky Way. X-ray sources in the central region of the Andromeda Galaxy Yoshiyuki Fukuda (Graduation thesis at Tokyo University of Science) May 27, 2005 Tokyo Tech

2. Compact stars (White dwarf, Neutron star, Black hole) : These compact stars are too small to resolve from binary stars in visible band of light. But these compact stars and their accretion disks can be observed as bright point source in X-ray band. White dwarfNeutron starBlack hole original mass ～ 8～ 8 8 ～ 30 30 ～ mass1.42 radius6400km10km20km degenerate pressure electronneutron

3. I investigated the central region of the Andromeda Galaxy to know the number and the types of the compact stars. Data were fitted with their energy spectrum for blackbody model and accretion disk model. (Data were taken by Chandra Spacecraft in 2001) To study compact stars enable us to know about their original character at one time. We can know the ancient character of Andromeda Galaxy. ↓