FIGURE 2.4.2 The nearby spiral galaxy Messier 81 imaged with the Spitzer Space Telescope in the infrared (left) and the Galaxy Evolution Explorer (GALEX) in the ultraviolet (right). This galaxy is very similar to our Milky Way. New stars are forming out of gas clouds concentrated in the spiral arms. A dormant supermassive black hole lurks in the bright central region. SOURCE: Left—NASA/JPL-Caltech/K. Gordon (University of Arizona), S. Willner (Harvard-Smithsonian Center for Astrophysics), and N.A. Sharp (NOAO/AURA/NSF). Right—NASA/JPL-Caltech/J. Huchra (CfA).

FIGURE 2.4.3 Hubble Space Telescope image of the Orion Nebula. This is a nearby region in the Milky Way galaxy where new stars are forming out of a surrounding gas cloud. Intense radiation from these young stars is causing the natal gas clouds to glow in a swirl of vibrant colors. SOURCE: NASA, ESA, M. Robberto (STScI/ESA), and the Hubble Space Telescope Orion Treasury Project Team.

FIGURE 2.4.4 An image of the nearby galaxy Messier 82 produced using the Hubble Space Telescope, the Chandra X-ray Observatory, and the Spitzer Space Telescope. The galaxy (as seen in green) has such a large number of supernova explosions that they are blasting out much of the galaxy’s gas supply (as seen in red and blue). Such events play a critical role in the life cycles of galaxies. SOURCE: X-ray—NASA/CXC/JHU/D. Strickland; Optical—NASA/ESA/STScI/AURA/The Hubble Heritage Team; IR—NASA/JPL-Caltech/University of Arizona/C. Engelbracht.