Life Cycle of Stars

An elderly man stricken with terminal cancer is sitting on his porch pondering life. As the Sun fades away in the distance a tear comes to his eye, because he knows his eternal sun is about to set for its last time. Realizing this could be his last moments the man stays on the porch well into the night. He gazes at the stars above and begins to wonder about how the beautiful twinkling stars above came to be. He decides to phone his son, Tom, an astronomer to come by and star gaze with him. Twenty minutes later Tom arrives and sits in the rocking chair beside his father. Tom gazes to the heavens, when his father asks, "Tom, do the stars burn for ever?" Tom replies to his father, first we are going to discuss the importance of light and other electromagnetic waves. Then we will explore where stars fit in the hierarchy of the universe. Finally we will examine the composition and life cycle of a star, along with how the process recycling materials is related to the structure of the Milky Way Galaxy and to the origins of the universe. The two men settle into their chairs as Tom begins to explain the importance of light and electromagnetic waves.

Tom points to the porch light and starts to explain how the light transmits from the bulb to their eyes. The son begins explaining that visible light is transmitted through a form of electromagnetic wave. There is a big range of light and only a small portion is visible. The wavelength and frequency determines where on the electromagnetic spectrum a light will be. Unseen light beyond the visible blue range has smaller wavelengths with a faster frequency, and the unseen light beyond the visible red range has longer wavelengths and a slower frequency. For instance; gamma rays, X-ray and ultraviolet wavelengths are shorter and a higher frequency than visible light so they are beyond the blue spectrum and unseen. While on the other side of the spectrum there are infrared and radio wavelengths which are longer and a slower frequency than that of the red spectrum which makes them unseen. To fully understand stars and the universe Toms colleagues need to be able to detect all forms of electromagnetic waves and not just the visible range. To do this they must use different instruments and devices such as antennas and telescopes. For more of a background on stars Tom decides to explain where stars fit into the hierarchy of the universe.

Tom begins with our solar systems explaining how the moons orbit the planets, which orbit the Sun, which in turn orbits the Milky Way Galaxy center, which orbits the universe center. But for this discussion he decides to focus on the stars and up the hierarchy. He explains how the stars like our Sun are one of the lowest levels of the universe. A bunch of stars make up a galaxy, there can be millions to billions of stars in each galaxy. The next level on the hierarchal chain would be clusters; these clusters are made up of galaxies which all orbit the universe together as one. Finally, the universe is everything from center to end. Now that the father knows where the stars are in hierarchy, he wants to know the characteristics of the stars.

Tom clarifies that a star is a gigantic, brilliant sphere that produces light and energy. He explains that our sun is a star which supplies Earth with light and heat. The Sun and most other stars are giant balls of hot gas and a substance known as plasma. Another forms of stars are called white dwarfs and neutron stars, which consist of subatomic particles or closely packed atoms. These stars are consequently much denser than anything on Earth. Neutron stars are the smallest stars with an average radius of about 6 miles, apposed to a supper giant which can have a radius of about 1,000 times that of our Suns 435,000 mile radius. Tom also explains that there are five main characteristics to differentiate between different stars. Those characteristics are the stars, size, color, surface temperature, mass and brightness. The distinctive traits are related to one another in an intricate way. Color depends on surface temperature, and brightness depends on surface temperature and size. The mass affects the speed stars produce energy and the energy affects the surface temperature. To make these associations easier to understand astronomers developed a graph called the Hertzsprung-Russell (H-R) diagram. As the two men continue to stare at the night sky the father begins to cough and Tom begins to worry. After a few minutes the older gentleman