Exploring the solar system was made possible by innovations after the discovery and acceptance that Earth was not at its center. In particular, the science of spectroscopy—which can “determine motions, temperatures, rotation rates, and especially the chemical properties of objects” (86). Spectroscopy utilizes light, the range of spectra, to make its measurements. Its application to astronomy created the word “astrophysics” in the 19th century. In the 20th century, technology was developed that allowed for the launch of probes and the collecting of physical samples; thus, knowledge of the solar system continues to expand.

The solar system—the sun and all eight planets (plus their various moons and other space debris, like asteroids)—was formed at once. The sun of this particular solar system was born out of the death of another star 4.5 billion years ago. The sun’s thermonuclear core is the sole thing that keeps it from collapsing in on itself; eventually, it, too, will die—but not for about another 5 billion years. The sun itself possesses its own atmosphere, as does the Earth; however, its atmosphere consists of solar wind with solar flares and intense heat coming off the surface.