This image of our Milky Way galaxy shows various types of gas, charged particles and dust. The composite image is constructed from observations made at microwave and millimeter wavelengths of light, as seen by the Planck satellite, a European Space Agency mission with significant NASA contributions. In this view, different colors represent various materials and types of radiation. Red shows dust that gives off a thermal glow, and makes up the most abundant of the dust features shown. Yellow shows carbon monoxide gas, which is concentrated along the plane of our Milky Way in the densest clouds of gas and dust that are churning out new stars. Blue indicates a type of radiation called synchrotron, which occurs when fast-moving electrons, spit out of supernovas and other energetic phenomena, are captured in the galaxy's magnetic field. The electrons spiral along the magnetic field, traveling near the speed of light. Green shows a different kind of radiation known as free-free. This occurs when isolated electrons and protons careen past one another in a series of near collisions, slowing down but continuing on their own way (the name free-free comes from the fact that the particles start out alone and end up alone). The free-free signatures are associated with hot, ionized gas near massive stars.