Dark digits

In April this year, astronomers working on the Event Horizon Telescope captured the first direct images of a black hole and its “shadow” – the glowing ring of gas and dust trapped in a disc around them. Inspired by this revolutionary discovery, Physics World reader Michael Metcalf has created a variant of a traditional sudoku so that it begins with a central shadow surrounded by a bright region. Test your mettle over the holidays. We will share the solution next February.