Astronomy Picture of the Day
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July 2, 1995
The Cartwheel Galaxy
Picture Credit: NASA, Hubble Space Telescope
The Cartwheel Galaxy shows a ring that is the result of a
collision between a small and a large galaxy. After a small galaxy has moved
through a big galaxy - in this case one that probably resembled our
own Milky Way - a
star formation wave moves out from the impact point like ripples
across the surface of a pond. When galaxies collide it
is rare that any two stars actually collide. Gravity, however, causes
density waves to move out through the galaxy
which in turn triggers the formation of hot, bright young stars,
producing the ring that we see in this picture.
For more information see
NASA, Hubble Space Telescope Scientific Institute press release.
The Great Nebula in Orion
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