So its complicated...<p>They are all &quot;real&quot; and very useful in different ways. Its important to remember that they are all maps of different thing depending on how transparent the things they are mapping are. For example the dark clouds in the optical are nearby cold &#x2F; dense clouds of gas where stars are forming. They block almost all the visible light from the stars behind them. If you want to study star formation (my PhD) you can learn a lot by looking at how they absorb light, or you can look at a different wavelength and look inside &#x2F; through them (microwave).<p>You have to remember that the maps are measuring how bring sources are (at each wavelength) filtered by how absorptive the stuff along the line of sight is (at each wavelength). In the same way that images of far away galaxies are looking back in time, images at different wavelengths probe different distances and temperatures in our galaxy, but in a much messier way.