We think of comets as beautiful glowing balls of light streaking across our skies with their long sweeping tails, yet comets are so much more than just a cosmic firework display. Comets have a uniquely important place in modern science. As time machines from the early universe, they could hold the key to unlock the secrets of the cosmos. Comets could even be the origin of life itself. We follow the incredible odyssey of a comet as it sails through the solar system, watching it's every move as it evolves from a dormant chunk of ice and rock into a tumbling, violently active nucleus engulfed in a gaseous haze. What we learn is a revelation; comets are even more mysterious and fascinating than we had ever imagined.
Today we’re talking about our galactic neighborhood: The Milky Way. It’s a disk galaxy, a collection of dust, gas, and hundreds of billions of stars, with the Sun located about halfway out from the center. The disk has grand spiral patterns in it, formed by the traffic jams of stars and nebulae, where stars are born. The central region is shaped like a bar, and is mostly old, red stars. There’s also a halo surrounding us of old stars.