Sci 151 - Science of Stars

Science of Stars

Ted Smith

SCI/151

May 23, 2016

Prof. Ken Watanabe

Introduction    

This paper is about the science of stars.  This paper is going to discuss how to determine properties of distant objects, explain the composition, temperature, speed, and rotation rate of distant objects.  This paper will also explain the properties of stars in the HR Diagram.  Finally this paper will also discuss the life cycle of the sun and its current status to date.

How to Determine the Properties of Distant Objects

There are many different types of tools that help with determining the different types of properties of distant objects, the use of spectroscopy helps determines the composition of a distant object, using Wien’s Law helps astronomers to determine temperature of distant objects, the Doppler Effect helps astronomers determine the speed of a distant object, and by using the distant objects Doppler-shift along with the spectrum of the object astronomers can determine the rotation rate of the object.

Composition  

When astronomers determine the composition of a distant object, most astronomers will turn to the use spectroscopy. Spectroscopy studies interactions between matter and electromagnetic radiation.  The spectroscopy was what was used to help astronomers discover that the sun was made up of mostly helium.  Because of the spectroscopy astronomers have a better understanding what stars are made up of mostly hydrogen, and helium, with other elements.  Spectroscopes today have very high resolutions and show astronomers the spectral lines in detail.  Spectroscopes can now show astronomers the presence of a line, and are often able to determine the relative amounts of the different types of elements and molecules that are present.  By using this astronomers are now able to determine the metallicity of a star.  

Temperature  

The most common way astronomers today determine the temperature of an object is by using Wien’s Law.  “In 1980 Wilhelm Wien used this method to estimate the effective temperature of the sun 6,000 K which is much closer than the previous estimate of 10,000 K that was predicted with using Stefan-Boltzmann law of radiation” (ASTRO, 2015).   The point of Wien’s Law is, if astronomers can measure the wavelength of the maximum intensity from a spectrum, astronomers can also calculate the temperature.  By using this method astronomers can determine the stars temperature more effectively by using the stars spectrum.

Speed

Astronomers use the Doppler Effect to measure the apparent shifts in wavelengths of distance objects to determine the speed and the distance the object is. The formula astronomers use is C=speed of light= 3.0 * 10^8 m.s^-1 and v is non relativistic in speed.  V is positive for receding objects and negative for those approaching. The Doppler Effect can be associated with the same way that sound is perceived from a vehicle passing by, or how loud music is the closer it becomes.  

Rotation Rate