Finding a copyright free picture of space

For my green screen dancing shot, I would like to find a picture of space to place behind them. I am hoping to find a copyright free picture of a nebula or of the stars. I think a colourful picture would suit the video more, so I will try and find one.

I have come across this picture:

http://www.public-domain-image.com/space-public-domain-images-pictures/orion-nebula-space-galaxy.jpg.html

I think this picture suits my video perfectly. It is a mass of different colours, lost within space so relates to the feeling of hopelessness that can be seen in the songs lyrics, but also connects to the feeling of hope that is provided as well.

The picture is also copy right free, which is extremely important as it is available to use for any purpose and is not illegal.

I wanted to include a picture of space as I wanted to relate to the lyrics in the song about "an asteroid belt". It causes the audience to realise how expansive human's emotions can be and adds a new depth to the meaning of the video.