The Milky Way, along the Galactic plane
Seen in Wavelengths from Radio frequency through Gamma rays
- Radio map at 408 Mhz, showing mainly emission due to scattering of free electrons in the interstellar plasma (i.e. hot gas). The large arc is due to a nearby supernova remnant.
- 21 cm radiation map, showing the distribution of neutral Hydrogen gas in the galactic disk, and a few nearby arcs from recent supernovae.
- Distribution of H2, or molecular Hydrogen.This maps the “cold” gas in the Galaxy, from which stars will eventually form. The actual observed molecule is CO, rather than H2, which is very difficult to detect directly. The star forming layer of gas is remarkably thin. Infrared maps at the wavelengths 12, 60 and 100 microns.
- Infrared emission predominately comes from interstellar dust which is “warmed” to a few 10’s of degrees Kelvin by the ambient radiation field of the Galaxy’s stars.
- Near Infrared emission is dominated by cool stars. Since these are typically either old or long-lived stars, this is our best view of the Galaxy with the hot, bright young stars removed. Dust absorption at these wavelengths is very low and we get a clear view all the way to the Galactic center of the disk and bulge.
- Optical image of the Galaxy showing the huge effects that dust absorption has on our view of the central regions of the Galaxy. The emission is dominated by young and old stars and by the effects of dust.
- X-ray image taken by the Rosat satellite. This view, less clear than the others is dominated by supernova remnants (some of the arc-like features) as well as individual sources of X-radiation from close binary stars or black hole candidates.
- Gamma ray view of the Galaxy is dominated by emission from Cosmic Rays (high energy particles) decelerating in the interstellar medium
SOURCE: Chris Flynn’s Galactic Dynamics: Discovering the Milky Way