Science of Stars Essay

1117 Words Apr 30th, 2012 5 Pages
Science of Stars
This paper is about the science of the stars. In this paper I will address how astronomers determine the composition, temperature, speed, and rotation rate of distant objects. I will briefly explain the properties of stars in the H-R diagram from Chapter 15 of the course textbook “The Cosmic Perspective”. I will also summarize the lifecycle of the Sun and identify where the Sun is in its lifecycle.
Studying Distant Objects
Astronomers study light which comes from distant objects to determine its composition, temperature, speed, and rotation of distant objects. This process is called spectroscopy. Spectroscopy was first used to study celestial objects in 1863 by William Higgins. By using this process he
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This measurement is done by utilizing the Inverse Square Law for Light. Simply put, the farther away you get from the object the dimmer it will appear.
H-R Diagram
Danish astronomer Ejnar Hertzsprung and American astronomer Henry Noris Russell noticed the relationship of the stars surface temperature and its luminosity. They used this relationship to develop a type of graph to identify where each star is in its lifecycle.
The graph is essentially based on two properties of the stars. One property is the star’s surface temperature, also known as its spectral type. The surface temperature is plotted on the x-axis or horizontally. Bluer stars have cooler temperatures, while redder stars are hotter. We are able to determine a star’s surface temperature by examining the wavelength of its peak intensity otherwise known as Wein’s law. The second property of the star graphed on the H-R diagram is the star’s luminosity or amount of energy radiating from it. This property is plotted on the y-axis or vertically and usually based on a ratio-scale with the reference point being the Sun. By graphing these two properties of stars we are able to map out where most stars are in their lifecycle.
Lifecycle of the Sun
The Sun which is a low mass star is approximately 5 billion years old and halfway through its lifecycle. Its entire lifecycle is made up of the following stages: protostar, main sequence, red giant, and lastly a white dwarf. These stages are…