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How do we get such beautiful, ornate, and symmetrical shapes of galaxies — pinwheels, ovals, spirals, and central bars — when the same gravitational forces are at work as those that affect Earth and the Sun's other planets?

Ron Herron, Santa Barbara, California
RELATED TOPICS: GALAXIES
Shapes of galaxies
This question illustrates fascinating properties of the gravitational force. A single spherical object, such as Earth or a star, has its shape due to gravity. So at first we might expect all objects held together by gravity should have roughly spherical shapes.

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