Ribbons and Pearls of Spiral Galaxy NGC 1398

Why do some spiral galaxies have a ring around the center? Spiral galaxy NGC 1398 not only has a ring of pearly stars, gas and dust around its center, but a bar of stars and gas across its center, and spiral arms that appear like ribbons farther out. The featured image was taken with ESO's Very Large Telescope at the Paranal Observatory in Chile and resolves this grand spiral in impressive detail. NGC 1398 lies about 65 million light years distant, where light year is a measure of distance, not time. The photogenic galaxy is visible with a small telescope toward the constellation of the Furnace (Fornax). The ring near the center is believed to be an expanding density wave of star formation, caused either by a gravitational encounter with another galaxy, or by the galaxy's own gravitational asymmetries. What appears to be star formation, however, does not mean stars are actually forming there.