In a case of life imitating art, a 100-metre-wide asteroid has triggered global planetary defence procedures for the first time, after telescope observations revealed it had a chance of colliding with Earth in 2032. To find out what happens now and how worried we should be, Ian Sample hears from Richard Binzel, a professor of planetary sciences at MIT and inventor of the Torino scale, which is used to categorise the threat posed by objects such as asteroids and comets. Help support our independent journalism at theguardian.com/sciencepod