The faint band of light our ancestors called the Milky Way turns out to be the disc of our own galaxy, seen edge-on from the inside — a spinning city of a few hundred billion stars, held together by gravity and a great deal of dark matter. This episode traces how galaxies form, why so many are elegant spirals, and how ours was assembled from smaller pieces over billions of years.

You'll come away understanding what a galaxy is, the difference between spirals and other shapes, the role of the giant black hole at our galaxy's centre, and how galaxies grow by merging.

Talking Science is sponsored by Kinsoft. Visit www.kinsoft.com.au

Further reading: NASA – "Galaxies"; ESA Gaia mission – mapping the Milky Way; European Southern Observatory – Milky Way ov ...