As part of an all-sky astronomical survey, NASA’s Wide-field Infrared Survey Explorer (or WISE) satellite took over 2.7 million images and beamed back 5 trillion bytes of data to eager astronomers back on Earth. This composite image is made up of 18,000 images covering the sky and shows more than 560 million stars and galaxies! You’ll notice that the prominent Milky Way Galaxy runs horizontally at the centre of the map.
The mosaic image has an oval shape and that is because of the method used to render the 3D sky onto a 2D map.
The sky can be thought of as a sphere that surrounds us in three dimensions. To make a map of the sky, astronomers project it into two dimensions. Many different methods can be used to project a spherical surface into a 2-D map. The projection used in this image of the sky is called Aitoff, named after the geographer who invented it. It takes the 3-D sky sphere and slices open one hemisphere, and then flattens the whole thing out into an oval shape.
Have a look at the full image after the jump.