Not so long ago, astronomers thought of the Milky Way’s central bulge as an old folks home where mostly ancient stars congregated and slowly moved about. But more recent observations, including this spectacular view captured by the Hubble Space Telescope, and an analysis of about 10,000 suns in the bulge reveal a much more dynamic environment where stars of various ages move about at different speeds. The faster, younger stars may have been captured as the Milky Way cannibalised smaller galaxies, mingling with older, slower-moving suns.
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A galactic mega-merger
The subject of this NASA/ESA Hubble Space Telescope image is known as NGC 3597. It is the product of a collision between two good-sized galaxies, and is slowly evolving to become a giant elliptical galaxy. This type of galaxy has grown more and more common as the universe has evolved, with initially small galaxies merging and progressively building up into larger galactic structures over time.