What does a supernova remnant look like 40000 years after the star has exploded? Here is the answer. The diameter of the remnant is now 140 light years. Expansion of the star dust still continues so that the nebula will be getting dimmer and dimmer over time until all its material will be part of the interstellar medium again. Some of the material will end up in new star-forming regions and since the nebula contains many heavy elements, such as oxygen, carbon, iron etc., it may become part of a planet or even part of life in some form or another. This is how the heavy elements came to Earth too; they have all been cooked long ago in the stars and spread around the galaxy after a star became a supernova or a planetary nebula.
In reality the nebula is much dimmer than on this image, but with help of a long exposure time you can simply see much more on images like this than you'd ever be able to see with your own eyes.If interested, read more about: Supernova