Do you have a pet? What is it called? (If you don’t have a pet, imagine what you would it if you did have one.) Now imagine your pet giving birth to ten babies. What would you call them? Now imagine each baby giving birth to ten more babies. What would you call them all?

If this continued, it probably wouldn’t be long before you ran out of names. Imagine trying to name all the cosmic wonders in the night sky. You’d need an endless imagination.

Just a few hundreds of the brightest objects in space have been given traditional names, like Jupiter, Bellatrix and Andromeda. Most other objects are labelled with a mix of letters and numbers. It’s a little bit like shopping catalogue with the letters being like a codename for the catalogue, and the numbers being a page number. For example, the cluster of stars in this picture has the unfortunate name IC4651.

This cluster was first noted down in the Index Catalogue, this is where the IC in its name comes from. The following number gives us a way to find the cluster in the catalogue. For example, this star cluster was the 4651st object listed in the Index Catalogue. The names are not very exciting, but it’s easier than trying to think of millions of different names!

Astronomers have been noting down the names, locations and features of space objects for a long time. The first cosmic catalogue was created around 4,000 years ago by the Babylonians! And new star catalogues are still being created today. In 2014, astronomers made a catalogue of over 84 million stars in our Milky Way!