Dusting Spiral Galaxies

How much dust is in spiral galaxies? Does it block out much of the starlight? Because astronomers rely on an accurate knowledge of galaxy properties to investigate a wide range of problems, like galaxy and quasar evolution and the nature of dark matter , answers to simple questions like this are key. This striking, detailed Hubble Space Telescope image of dust in the outer reaches of a foreground spiral galaxy (left) back lit by an elliptical galaxy offers an elegant approach to providing the answers . As expected, dust lanes in the foreground galaxy seem to be associated with spiral arms. But surprisingly , many dust regions are not completely opaque and the dust is more smoothly distributed than anticipated . This “overlapping” pair of galaxies is cataloged as AM1316-241 and is about 400 million light-years away in the constellation Hydra .