Quasars and AGNs
Near the edges of the observable universe, there are galaxies so energetic that they launch jets of ions and radiation far into space. The key to their immense energy is that they contain super-massive black holes at their centres, slowly devouring the surrounding galaxy. These super-massive black holes are known as active galactic nuclei (AGNs) and are only found in the outer reaches of the universe as they were the first galaxies to form after the universe came into existence.
What are the different types of Active Galaxy?
Active galaxies (galaxies containing AGNs) come in 4 main types. The first of these are radio galaxies - galaxies which emit intense radio waves in the form of two symmetrical lobes on either side. The second type of active galaxy is Seyfert galaxies - bright galaxies which emit particularly strong infrared or x-ray radiation. The third type are quasars (quasi-stellar objects) - compact galaxies which emit intense radiation in all wavelengths between x-rays and radio waves. The final type of active galaxy is blazars - galaxies which are closer and more compact than quasars, which emit bright light in all wavelengths of the electromagnetic spectrum.