April 20, 2017

Hi! I took a brief hiatus last week for spring break, but I am back now. We were notified today that there would be four more posts (including this one) before the conclusion of the senior project.

Addressing Mr. Hrin's questions from the previous week, I do plan on following up with my question regarding how theoretical models are created. How does one generate a model that future research is based on before knowing what is "correct"? This question always puzzled me, but I realize now that it is created through theories and many repeated experiments. For example, Kapteyn came up with his model of our Milky Way by using first the proper-motion technique (by measuring the non-periodic motion of stars) and the parallax method (measuring how Earth's revolution around the sun affected or shifted star's positions) but did not factor in the absorption of starlight by interstellar medium. Kapteyn studied approximately 200 areas to reach his conclusion that the Sun was located relatively close to the galactic center.

Harlow Shapley, a fellow astronomer, questioned Kapteyn's model and drew the correct conclusion of the size of the Milky Way and the position of the Sun within the galaxy. How he came up with his model was by studying globular clusters and concluding that if globular clusters were common and evenly distributed around the center of the galaxy, the Sun could not be near the center.

Chemical composition of galaxies is what my project is mainly on, and the concentration of metals is related to decreasing stellar age. With only a couple weeks left, I will be wrapping up my project. Next week, I'll be writing about the significance of my project in broader terms of how it relates to the history of the universe and even the existence of extraterrestrial life. Stay tuned!