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Colliding Galaxies. Ellipticals generally have old stars (type II). This suggests that they were formed first. The center of spiral galaxies also have type II stars. The disk of a spiral galaxy has type I stars that are young. Star Ages. Close Encounters.
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Ellipticals generally have old stars (type II). This suggests that they were formed first. The center of spiral galaxies also have type II stars. The disk of a spiral galaxy has type I stars that are young. Star Ages
Close Encounters • Galaxies are attracted to each other by gravity. • If two ellipticals pass each other gas and stars are pulled. • The galaxy is distorted as it rotates.
New Star Regions • As an elliptical passes through, the stars do not collide. • The gas and dust in the two galaxies collide. • The increased density and gravity creates new stars.
Ring Galaxies • One galaxy may pass through another. • The collision forms a ring of stars and gas. • Gravity can pull the stars in, forming spiral arms.
Forming Spirals • Computer simulations are used to see the effect of collisions. • A near miss forms a spiral galaxy (top sequence). • A direct hit forms a ring galaxy (bottom sequence).
History in Shapes • Spiral galaxies are created by collisions of galaxies. • Many spiral galaxies • Collisions common • Irregular galaxies occur during collisions. • Lasts about 100 million years • The resulting spiral will last for billions of years.