Figure 18-8: R I V U X G
Spiral Galaxies Spiral galaxies, like our own Milky Way Galaxy, consist of stars, gas, and dust that are largely confined to a flattened, rotating disk. (a) This face-on view of M83 shows luminous stars and H II regions along the spiral arms. (b) This edge-on view of NGC 891 shows a dark band caused by dust in this galaxy’s interstellar medium. Although in different parts of the sky, both galaxies are about 7 million pc (23 million ly) from Earth and have angular diameters of about 13 arcminutes.
Spiral Galaxies Spiral galaxies, like our own Milky Way Galaxy, consist of stars, gas, and dust that are largely confined to a flattened, rotating disk. (a) This face-on view of M83 shows luminous stars and H II regions along the spiral arms. (b) This edge-on view of NGC 891 shows a dark band caused by dust in this galaxy’s interstellar medium. Although in different parts of the sky, both galaxies are about 7 million pc (23 million ly) from Earth and have angular diameters of about 13 arcminutes.
(a: Australian Astronomical Observatory/David Malin Images; b: Instituto de Astrofísica de Canarias/Royal Greenwich Observatory/David Malin)