Question: what makes a galaxy/ supernova spiral and have so many colours

Jen Gupta answered on 16 Jun 2011:

I don’t think anyone knows why spiral galaxies have spiral arms! There are lots of theories about it but I don’t know enough about it to be confident enough to say which one is right. Supernovae actually normally look round. They are caused by a star exploding and the explosion goes in all directions so you get a shell (like a bubble) of material being blown away from the star.

Colours in astronomy pictures is a tricky one. A lot of the times, the colours that you see in these pictures are false colours and I think astronomers often choose the prettiest combinations! We can look in space using telescopes that are sensitive to different types of “light” not just the visible light that ours eyes can see. When we make pictures of glaxies or supernovae it often combines the images we get in these different types of light and use a different colour to represent the visible light, the x-ray etc. It’s kinda like if you combined a photo of yourself with an x-ray and a night vision image!