Lesson Three : The Milky Way: Our Own Radio Galaxy
The radio emission of the Milky Way is created by synchrotron radiation. In a radio mapping of our galaxy, distinct sources are not apparent. Rather, a radio mp shows a halo of emission in regions that are rich in cosmic rays; particles with incredible amounts of energy which are thought to originate during supernova explosions. These particles encounter strong magnetic field lines around cosmic objects and begin circling them and accelerating in ever-widening spirals. As these particles spiral outward, the electrons and protons emit synchrotron radiation.Radio maps of our galaxy show the intensity of synchrotron radiation in our galaxy. A large amount of the matter in our galaxy is concentrated at the galactic center. Naturally, the galactic center contains more celestial objects with strong magnetic fields and more cosmic rays, and will emit more radiation than the periphery, or edges, of our galaxy.
Hydrogen is the most abundant element in the universe and constitutes much of the matter in our galaxy. Additionally, hydrogen has a unique "radio signature" with a wavelength of 21 centimeters that is easily measured by radio astronomers. By measuring the amount of hydrogen in our galaxy, radio astronomers can map the concentration of matter in the Milky Way, thereby allowing them to study the structure of the galaxy.