From Little Green Men to Big Green Galaxies!
There are seven billion other people living on this planet with you, people of many different ages, sizes and skin colours. Well, there are at least a million times more galaxies in the Universe than there are human beings! They come in many different varieties, too.
Recently, a new type of galaxy has been added to the list. These newcomers are bigger and brighter than anything else in space! And if that wasn't interesting enough, they also glow bright green! This has led astronomers to name them 'green bean' galaxies (look at the little green bean-like spot in the middle of this space picture).
These new galaxies are among the rarest objects in the entire Universe. We think that they shine so brilliantly because of a black hole at their centre. A black hole is a really tiny object with an enormous gravitational pull. Any material that comes too close is pulled into the black hole, never to be seen again. All galaxies probably have one of these monsters lurking at their centre, including our own galaxy, the Milky Way!
As a black hole sucks in nearby material, a disc forms around it. Picture the way water is sucked down a plughole. The disc grows hotter and hotter as it turns, causing it to blast out massive amounts of bright light. In this way, black holes are known to create extremely bright galaxy centres. But in the case of green beans, the entire galaxy is glowing!