As you know now, in radio astronomy we study objects in the sky by catching radio waves. But what does that exactly mean? And what do radio astronomers see when they look at the sky? We will tell you all about that here.
You know now that there are different kinds of radiation which can be seen at different frequencies. Each radiation can be seen with different kind of telescopes. Radio astronomers can look at different elements depending on the wavelengths they attempt to receive. If they study the same objects using different wavelengths, they will obtain images very different one from an other, allowing different analyses.
In the picture below you see the Crab Nevel in different kinds of radiation. The Crab Nevel exploded 1000 years ago as a supernova. This was observed by the Chinese and was one of the first reports of a supernova. This nebula is about 6500 lightyears from Earth. As you can see the shape of the nebula is different in each radiation. You can also see different kind of structures in the nebula. This gives us a lot of information about what is in the nebula.
Below you see an image of the Andromeda Galaxy, also in different kinds of radiation. From the top left to the bottom right you see: Radio, far infrared, near infrared, visible, ultra-violet and X-ray light.
Some galaxies were discovered in radio light first, such as Cygnus A (in the constellation of Swan the strongest radio source, and one of the strongest sources in the sky). At high frequencies we see a small dot in the middle, with two huge rays that end in some kind of dumbbell. This is not light as it is made in the sun (nuclear fusion), but light that arises because matter moves enormously fast in a magnetic field. This intensity can only occur if there is a black hole at the base.