mosaic | Onelargeprawn

A WISE View of the Entire Sky

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.

You might not believe it, but this is an actual photograph reported to have been taken back in 2006 as the Cassini space probe sheltered in the shadow of Saturn. It was 2.2 million kilometers away from the gas giant when it took the photograph.

Astronomy Photo of the Day explains the image thus:

The robotic Cassini spacecraft now orbiting Saturn drifted in giant planet’s shadow for about 12 hours in 2006 and looked back toward the eclipsed Sun. Cassini saw a view unlike any other.

First, the night side of Saturn is seen to be partly lit by light reflected from its own majestic ring system. Next, the rings themselves appear dark when silhouetted against Saturn, but quite bright when viewed away from Saturn, slightly scattering sunlight, in this exaggerated color image.

Hit the jump to see the full image.