Researchers investigate stellar populations in the central region of the Andromeda galaxy

German astronomers have conducted a study of the central bulge of the Andromeda galaxy and analyzed its stellar populations. The research could improve our understanding of the bulge's structure and formation history. Results of the study are presented in a paper published July 24 on the arXiv pre-print repository.

Located some 2.5 million light years away from the Earth, the barred spiral Andromeda galaxy, also known as Messier 31, or M31 for short, is the nearest major galaxy to the Milky Way. Due to its proximity, M31 is an excellent target to study the detailed evolutionary history of large spiral galaxies.

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Credit: Adam Evans.

The Andromeda galaxy.

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Also known as the Andromeda Galaxy, M31 is the largest and closest such galaxy to our own. It's more than 220,000 light-years across and lies 2.5 million light-years away in the constellation Andromeda.

Between May 25 and July 26, 2008, Swift's Ultraviolet/Optical Telescope (UVOT) acquired 330 images of M31 at wavelengths of 192.8, 224.6, and 260 nanometers.


Some 20,000 ultraviolet sources are visible in the image, including M32, a small galaxy in orbit around M31. Dense clusters of hot, young, blue stars sparkle in the disk beyond the galaxy's smooth, redder central bulge.

Star clusters are especially plentiful along a ring about 150,000 light-years across.

This zoom dives deep into the nucleus of the neighboring spiral galaxy M31, also known as the Andromeda galaxy. The sequence begins with a backyard constellation view and ends with the new Hubble Space Telescope image that centers on the 100-million-solar-mass black hole at the core of the galaxy and the young blue stars surrounding the black hole.

Astronomers are trying to understand how apparently young stars were formed so deep inside the black hole's gravitational grip and how they survive in an extreme environment.