Even if you’re not too clued up on your astronomical terminology, you’re likely to have seen an image of a spiral galaxy before because their winding formation looks so damn good. But these swirling star systems aren’t just photogenic, they’re fascinating too.

Back in the 1920s, Edward Hubble started working on a classification system for galaxies, known as the Hubble sequence. This is when he labelled some galaxies as spirals, lenticulars, ellipticals and irregulars.

Spiral galaxies, as you’d expect, all have a spiral-like formation around a central bulge in the middle, which comprises of older stars. This distinctive bulge is then surrounded by a flat, rotating disc of brighter, younger stars, gas and dust. Although it can’t be directly observed, scientists believe that lurking right there in the centre of a spiral galaxy’s bulge, there’s a supermassive black hole.

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