hubble images

[mr. piper]

why, when you see images from hubble etc. to they use artificial colours? i can understand if they are representative of something outside of the visible spectrum ie. x-rays. but when an optical telescope is used surley the object has colour of its own?

[Calvesy]

Even using an optical telescope, distant objects are so faint that it takes hours to accumulate enough red, green and blue light to make a colour image the human eye would recognise, albeit overexposed. However, as you correctly say, there are often more interesting things happening at wavelenghts we cannot see but there would be no point in printing these pictures using inks that reflect such radiation, hence the false colour.