Space is the next frontier for humankind. In recent years, its sounds and images have increased in quality due to technological advances, providing rich pickings for composers. This thesis explores astronomical phenomena in music composition with a focus on my composition portfolio. Beginning with the history of astronomy as a source of music inspiration, from Plato to Björk, this paper analyses my portfolio, the composition method and the ways in which space influences can be clearly demonstrated. The portfolio consists of five solo and piano accompanied works, one trio and a music theatre chamber work. Astronomical influences are shown in the use of sounds of nebulae, stars and galaxies based on electro-magnetic waves through a spectrograph, (courtesy of astronomer Paul Francis) and use of space images and concepts. These are incorporated into the compositions as accompanied sound, as a source of pitch material, contours of space images informing melodic shapes, as well as use of astrophysical concepts in a broader sense.