Black holes spew out powerful jets that span millions of light-years – we’re trying to understand their whole life cycle

An artistic representation of what a giant cosmic jet the size of the distance between the Milky Way and Andromeda could look like. Author provided, CC BY-SA

There is a supermassive black hole at the centre of nearly every big galaxy – including ours, the Milky Way (it’s called Sagittarius A*). Supermassive black holes are the densest objects in the universe, with masses reaching billions of times that of the Sun.

Sometimes a galaxy’s supermassive black hole “wakes up” due to a sudden influx of gas and dust, most likely supplied from a neighbouring galaxy. It begins eating up lots of nearby gas and dust. This isn’t a calm, slow or passive process. As the black hole pulls in material, the material gets superheated on a scale of millions of degrees, far hotter than the surface temperature of our Sun, and is ejected from the galaxy at near-light speeds. This creates powerful jets that look like fountains in the cosmos.