In 2017 the Event Horizon Telescope – a worldwide network of radio-telescopes – observed the supermassive black hole at the centre of the M87 galaxy, leading to the first ever image of a black hole, released in 2019. Now, using observations from 2017, 2018 and 2021, astronomers have found some changes in this now iconic image that could be caused by variations in the magnetic field around the black hole.