Today's Picture
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A mere 12.5 million light-years from Earth, irregular dwarf galaxy NGC 4449 lies within the confines of CanesVenatici , the constellation of the Hunting Dogs.About the size of our Milky Way's satellite galaxy the Large MagellanicCloud, NGC 4449 is undergoing an intense episode of star formation,evidenced by its wealth of young blue star clusters, pinkish star formingregions, and obscuring dust clouds in thisdeep color portrait .It also holds the distinction of being the first dwarfgalaxy withan identified tidal star stream, faintly seen at the lower right.Placing your cursor over the image reveals an inset of thestream resolved into red giant stars. The star stream represents the remains of a still smallerinfalling satellite galaxy, disrupted by gravitational forces anddestined to merge with NGC 4449.With relatively few stars, small galaxiesare thought to possess extensive dark matter halos.But since dark matter interacts gravitationally,these observations offer a chance to examinethe significant role of dark matter in galactic merger events.The interaction is likely responsible for NGC 4449's burst of starformation and offers a tantalizing insight into how evensmall galaxies are assembled over time.
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