Teddy

Relating the Chemical Composition of Stars to Their Absolute Magnitude

Stars are some of the most fascinating objects in the Universe. As far as we are concerned they are largely responsible for life on planets. So, finding the right star with the best conditions can actually give us a glimpse into which solar systems might be able to host a habitable planet. In order to find the system with the mystery life planet, first one would need to find out the elemental composition of a star. Stars have varying degrees of luminosity, temperature, and size all based upon their basic elemental properties. My question for this lab was whether or not the elemental composition of a star had an impact on its absolute magnitude. In short, my answer for this question was definitely yes. However, I also wanted to discover through research what this higher absolute magnitude meant, and what impact it would have on the stability and longevity of a star.

For this lab I decided to use absolute magnitude to measure luminosity, which means the overall luminosity from ten parsecs away. For this information I needed to use online research, after which I figured out the absolute magnitude of these stars. Now my experiment to discover what elemental compositions were responsible for this disparity in luminosity was on the table. To measure the elemental composition of the stars I used a spectroscope and a diffraction grater, which allowed me to measure the star's visual light spectra against the emission line spectra and helped me determine the star's elemental composition. I was able to hook up the diffraction grater and spectroscope to the Milton observatory and was able to take photos of stars' spectra.

In order to determine what elements were in each of the stars I photographed, I needed to compare an emission spectra chart to the spectra from the photos I took. I only needed to look for emission spectra of elements from hydrogen to iron, as stars can no longer commit to the process of nuclear fusion after they reach iron. In this comparison I found several intriguing trends. Stars with a higher metallicity, any element heavier than hydrogen or helium, tended to not only be far larger than their only hydrogen-helium emission counterparts, but they were far more luminous. I arrived at the conclusion that the reason this trend occurred was because those stars with higher metallicity had lost their process of nuclear fusion for lighter elements and now were resorting to fusing heavier elements, which was causing them to experience a phenomenon of stellar expansion and therefore increasing that star's absolute magnitude.