Figure 18-6: R I V U X G
Interstellar Reddening (a) Dust grains in interstellar space scatter or absorb blue light more than red light. Thus, light from a distant object appears redder than it really is. (b) The emission nebulae NGC 3603 and NGC 3576 are different distances from Earth. Light from the more distant nebula must pass through more interstellar dust to reach us, so more interstellar reddening occurs and NGC 3603 is a deeper shade of red. The two nebulae are about 1° apart in the sky.
Interstellar Reddening (a) Dust grains in interstellar space scatter or absorb blue light more than red light. Thus, light from a distant object appears redder than it really is. (b) The emission nebulae NGC 3603 and NGC 3576 are different distances from Earth. Light from the more distant nebula must pass through more interstellar dust to reach us, so more interstellar reddening occurs and NGC 3603 is a deeper shade of red. The two nebulae are about 1° apart in the sky.
(b: Stocktrek Images/Corbis)