"The Cosmic Microwave Background"
© Caterina Umilta
The picture shows a map of the cosmic microwave background (CMB), that is the first visible light after the Big Bang, as recovered from the Planck satellite maps. Observing the CMB helps us better understand the early phases of our Universe.
This image is obtained by naively combining five different sky maps. Why so many? Well, in order to remove all emissions that are not the CMB, such as the galactic emissions. As you can see, there is still a red line in the middle: that is our galaxy. It is in fact extremely difficult to correctly remove all the "polluters", such as the Milky Way, that hide the CMB and astronomers need to devise very clever algorithms in order to do so.
In fact, we can do much better than this! Go and check Planck CMB maps!