Radio Galaxies: The Peculiar, Secretive ‘Beasts’ Of Our Universe

Many of the galaxy images that humans see are basically optical images, such as the images seen from the Hubble Space Telescope. These images are made using telescopes that detect light in the wavelength range of our eyes. However, scientists have now designed radio telescopes that can use different parts of the electromagnetic spectrum such as the infrared or radio emissions.

When radio telescopes are used to look at the galaxies, it is observed that some galaxies have pairs of giant jets originating at their centre and extending out into the space. These jets are being called 'beasts' of the universe because they are powerful particles with lightning fast speeds. They are far larger than anything that may be visible in an optical image. They often elongate to multi-millions of times the size of the galaxy itself. Hence, there is no evidence of these jets in the optical images.

According to Huffington Post, it is not quite easy to understand these jets. Scientists might have a fair idea what these jets are and how they have been formed but they still have no clue regarding what initiates these jets in the first place. That's why a powerful Square Kilometre Array (SKA) radio telescope is now being built in Africa. It might help scientists explore the jets even more deeply due to its large size and scope.

How are the jets formed?

Galaxies exist in various shapes and sizes and all of them have a supermassive black hole at their centre. This black hole remains passive in certain galaxies. However, constant entrance of gas and dust into this black hole in some galaxies leads to a release of enormous amount of energy. This sometimes causes highly energetic streams of particles to eject from the centre of the galaxy. These streams are channeled by twisted magnetic fields.

Though the process of jet formation is understood, the reason for these jets to originate in the first place is unknown. Some observations indicate that such jets may be triggered due to the collision of two galaxies. But that certainly cannot be the case with all radio galaxies.

According to The Conversation, there are certain evidences that show how certain galaxies may stop ejecting these powerful jet streams, and then start the process again, thousands of years later. Scientists are not sure if all the radio galaxies go through these active and passive phases like this, or is it an unusual act.