Astronomers use the stellar spectrum to determine the composition and motion of stars. On the website, cnx.org the article “Using Spectra to Measure Stellar Radius, Composition, and Motion” explains how scientist use the spectra to measure how a star moves in space and what the chemical composition of that star is. Each star has its own composition of different elements. The absorption line in a spectrum of light determines which elements make up most of that star. Every star has a different pattern in their absorption lines because not every star is made up of the same elements. When measuring the spectrum of a star, scientists determine using its wavelengths. If a star is not moving then the wavelength of the elements will stay the same. If a star is moving away or toward us, scientist use what is called the Doppler effect. The spectral lines will shift to red if the star is moving away from us or will shift to blue if it is moving toward us.
This article correlates with our conceptual objective 7 stating that I can explain how astronomers use light to determine the chemical composition, the speed and direction of an astronomical object’s motion .In class we did a lecture tutorial on page 77 about Doppler Shifts. It asked if we could determine out of three absorption spectra which star was not moving relative to us, was moving away from us, and was moving toward us. The one that was moving away from us was the one that had absorption lines shifted more toward the red side of the spectrum. The one that was moving toward us had its absorption lines toward the blue side of the spectrum. The one that didn’t seem to move at all was relatively in the middle or not shifted toward red or blue.
This article gave a lot of information of how we determine the chemical composition and shift motion in stars. It used good pictures to show exactly how we can determine these things. I understand more on how scientist use the light spectrum to study the composition of stars and how the doppler effect tells them if a star is moving closer or farther away from us. I enjoyed reading it because it helped expand my knowledge on understanding this conceptual objective.