space.ogg - Mid-Air Machine - Creative Commons Attribution-ShareAlike
galaxy.png - NASA - Public Domain
ss.png - Pixabay - Pixabay License
css.png - Pixabay - Pixabay License
sat.png - NASA - Public Domain
asteroid.png - NASA - Public Domain
radio.png - NASA and Page Asgardius - Public Domain
supernova - NASA/JPL-Caltech - Public Domain