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