Professor Gaensler explains that light we can see and light we can't see, together make what is called the electromagnetic spectrum or spectrum of electromagnetic radiation (EMR).

Electromagnetic radiation assists our knowledge and understanding of the things in space that give out light. It is much more difficult to gain an understanding of things that don't give out light, like dark matter and dark energy.

Professor Gaensler uses radio telescopes because radio waves travel through just about everything in the universe. He also uses X-ray telescopes. These, because X-rays only come from the most energetic and extreme objects, those that flare or explode - phenomena Professor Gaensler wants to study. It is much more difficult to learn about the parts of universe that do not give out light

You need to use different types of telescopes to collect light of different wavelengths - radio waves through to gamma rays - to get a better picture of the universe: things like cool interstellar gas emits radio waves; most stars emit visual light; and extreme objects like neutron stars or black holes emit X-rays and gamma rays.

All calm interstellar gas emits in radio waves, so radio telescopes are needed; most stars. like the Sun emit visual light, so optical telescopes are needed; extreme objects emit in X-rays, so X-ray telescopes are needed. The best type of telescope to study an object depends on the sort of object, how hot it is, and how energetic it is.

The most exciting event Professor Gaensler has seen through a radio telescope was a huge star-quake. It was in late 2004, when he saw the cataclysmic explosion of a neutron star. The neutron star was fifty thousand light-years away. So, this explosion happened fifty thousand years ago, and when the light finally reached us the brightness of this neutron star was brighter than every other star in the Milky Way put together.