Today Phil’s explaining the stars and how they can be categorized using their spectra. Together with their distance, this provides a wealth of information about them including their luminosity, size, and temperature. The HR diagram plots stars’ luminosity versus temperature, and most stars fall along the main sequence, where they live most of their lives.
It’s a golden age for planet hunters: NASA's Kepler mission has identified more than 3,500 potential planets orbiting stars beyond our Sun. Some of them, like a planet called Kepler-22b, might even be able to harbor life. How did we come upon this distant planet? Combining startling animation with input from expert astrophysicists and astrobiologists, “Alien Planets Revealed” takes viewers on a journey along with the Kepler telescope. How does the telescope look for planets? How many of these planets are like our Earth? Will any of these planets be suitable for life as we know it? Bringing the creative power of veteran animators together with the latest discoveries in planet-hunting, “Alien Planets Revealed” shows the successes of the Kepler mission, taking us to planets beyond our solar system and providing a glimpse of creatures we might one day encounter.
Carl Sagan opens the program with a description of the cosmos and a "Spaceship of the Imagination" (shaped like a dandelion seed). The ship journeys through the universe's hundred billion galaxies, the Local Group, the Andromeda Galaxy, the Milky Way, the Orion Nebula, our Solar System, and finally the planet Earth. Eratosthenes' successful calculation of the circumference of Earth leads to a description of the ancient Library of Alexandria. Finally, the "Ages of Science" are described, before pulling back to the full span of the Cosmic Calendar. Note: This revised version of the series adds an introduction by Ann Druyan, in which she discusses some of the changes that occurred in the years after its broadcast.
We don't yet know where the edge of the universe is or what happens there; but thanks to cutting-edge technology and new discoveries, experts might finally reveal the secrets of the phenomena that can be found in deepest reaches of the cosmos.