ASTR 1346 1st Edition Lecture 14 Outline of Last Lecture I Einstein s Relativity A Length Contraction B Time dilation C Relativistic Mass II Neutron Star III Black Holes A Escape Speed IV Schwarzschild Radius and Event Horizon Outline of Current Lecture I Galaxies II Hydrogen Clouds III Parts of Our Galaxy A Galactic Center 1 Synchrotron Radiation B Galactic Bulge C Galactic Disk Current Lecture l A galaxy is a huge collection of stellar and interstellar matter stars gas neutron stars black holes etc isolated in space and held together by its own gravity Our galaxy is called the Milky Way because it looks like a River of Milk from horizon to horizon Our Solar System is in one of the spiral arms of our Galaxy ll Interstellar dust obscures our view into plane of disk at visual wavelengths Despite this hydrogen clouds can be detected by 21 cm radio waves emitted by changes in relative spins of electrons and protons Parallel spins are higher energy configuration and opposite spins are lower energy configuration lll These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute In our Galaxy we have the galactic center galactic bulge galactic disk and then the galactic halo which is outer debris A The Galactic Center is an active crowded place The stars are held in orbit by a 4 million solar mass black hole This is located near the constellation Sagittarius 1 Synchrotron Radiation are high speed electrons spiraling around the magnetic field B The Galactic Bulge is an oval region near the Galaxy s center It is 20 000ly across and 13 000ly thick Old and young stars mingle here giving off a yellow white color to the bulge with the younger stars toward the center More gas and dust are here which indicates vigorous star formation C The Galactic Disk is the flattest part of our Galaxy It s 100 000ly across and 2 000ly thick Spiral arms and dusty GMC s exist here There is ongoing star formation because of gas and dust It mainly contains young stars that re metal rich Population 1 stars this and open clusters and associations of stars gives the disk a blue white color Orbits of objects are circular uniform but different speeds around the center