Cernan Earth and Space Center
Grade Level: 7th grade and upLength: 37 minutes
The StarGazer is a multimedia program that combines stars, video, panoramic scenes, planetarium special effects and numerous astronomical photographs to illustrate the science of stars and the deeper meaning that astronomy holds for all of us. Nichelle Nichols (who played Lieutenant Uhura in the original Star Trek series) and Dr. James Kaler (Professor of Astronomy from the University of Illinois-Urbana) narrate this three-part personal look at astronomy.
The show begins with a child’s curiosity of the sky. At the age of eight, Jim Kaler had a conversation with his grandmother about the nature of the stars that he saw each clear night. In that conversation, young Jim Kaler not only learned from her that stars are actually round, not star-shaped, but he also took his first steps toward becoming an astronomer. In subsequent observations of the nighttime sky, he began to recognize that stars vary in their color as well as their brightness. He also “discovered” that some of the brightest stars are not really stars at all – they are planets. At the age of 12, Jim Kaler recognized Jupiter in the starry background and realized that because Jupiter takes 12 years to orbit the sun, its current location was the same as its location at the time of his birth. A year after that, Jim bought his first telescope, and despite the limitations of that tiny instrument, he found a number of stellar treasures, including the Ring Nebula, a ghostly smoke ring that is actually the expanding shell of gas from a dying star. His small telescope also revealed to him that our Milky Way galaxy is populated with countless, immense clouds of dust and gas, known as nebulae.
The StarGazer next discusses the science of gravity, light and the spectrum, and how we decipher the life cycle of the stars. James Kaler describes how an understanding of gravity is required to understand how star shines. He explains how a rocket overcomes the pull of gravity and that, while in orbit, the spacecraft is still falling, but its high speed counters the Earth’s gravitational pull. The spacecraft maintains a constant height above the Earth’s surface so long as it maintains this speed. In much the same way, the gravity of a star overcomes the tendency of a star to expand forever due to its high temperature. So long as the temperature and the mass of the star remain the same, it will maintain a certain size and color.
Next, the program explains how we can examine the light emitted by stars to determine their chemical composition and, by so doing, develop a way to classify stars. Black lines in the light spectra of stars, first discovered in the early 1800s, is the key to this understanding. Each star’s spectra peaks at different colors, revealing their internal chemistry, temperature, and even their fate when their fuel runs out. Stars are grouped into several spectral classes, which are based on their temperature. From the hottest stars (classified as O), the classes continue through B, A, F, G, K and M, which is the coolest class of stars. Stars also can be classified by their luminosity, or the total output of radiation emitted into space. By plotting the luminosity of a star versus its temperature, astronomers construct what is known as the Hertzsprung-Russell diagram. The H-R Diagram, as it is often abbreviated, reveals that most stars are located along a curved line that starts in the upper left-hand corner and continues toward the lower right-hand corner of the graph. These are the Main Sequence stars, which represent the middle-aged and stable stars, including our own sun. When stars begin to run out of fuel, they die, but not all stars die in the same fashion. Smaller stars like our sun will swell to a larger size and then gradually collapse. Larger, more massive, stars often die violent deaths, resulting in supernova explosions and sometimes ending their existence as black holes, which are briefly described in the program.
Finally, the program concludes by reflecting upon the deeper meaning of astronomy in our own lives. Dr. Kaler explains that although he is fascinated with the science of stargazing, he also recognizes how the stars can affect our lives. The parallel between the lives of stars and the lives of us humans is a profound discovery, and he encourages everyone to “be the star gazer that is within you.”
After The StarGazer has concluded, the Cernan Center show operator will use the star projector to show audiences the current night sky and the major stars, constellations and planets that can be seen on the next clear night. A brief question-and-answer period follows this live segment of the presentation.
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