What’s not to love about black holes? They’re the subject of Muse songs, make for great plot devices in any sci-fi franchise, and are some of the most mind-blowing features of Einstein’s general theory of relativity. If asked to picture one right now, you’d surely have no problem – but does the version in your head, gifted to you by fiction and fantasy, match up with what’s really going on out in deep space? We now know the answer, and it’s a beautiful yes.

Up until 2019, all visual evidence of black holes had been indirect. Astronomers observed groups of stars orbiting around central points in our galaxy, as well as massive jets of matter spewing out from either side of them. Scientists inferred that these events correspond to black holes, each exerting a gigantic gravitational pull, but had not yet developed a powerful enough telescope to image them directly. Technically, this is still true. Since a telescope’s resolution is proportional to its size, imaging the supermassive black hole at the centre of the M87 galaxy - 55 million light years away - would have required a telescope the size of Earth. If you’re wondering why you don’t recall your home being converted into wing #4721 of the global telescope, that’s because eight different observatories from around the world were used instead, coordinating remotely to turn the Earth into a single radio dish. Each of the independent observatories in the Event Horizon Telescope (EHT) collaboration took repeated readings in the direction of M87 beginning in 2017, gathering more data than any experimental procedure in history. Combining these readings at the Max Planck Institute for Radio Astronomy in Bonn, Germany and the Massachusetts Institute of Technology’s Haystack Observatory in Westford took over two years.

The EHT takes its name from possibly the most recognisable feature of a black hole. What looks to us like a dark spot is actually the event horizon: the boundary around a black hole beyond which no light or radiation can escape. The ring of light we see around the event horizon is called an accretion disc: masses of matter spiralling towards the black hole, pulled in by the force of gravity. Amazingly, the gravitational pull of a black hole is so strong that the space surrounding it is warped, causing all light around it to bend and make the event horizon look five times larger than it really is. This phenomenon is also what causes the black hole to look lopsided, as the light on the side rotating towards the telescope appears brighter than the side rotating away.

The first image published by the EHT back in 2019 was given a revamp in 2021, and once again in 2024. This time, researchers measured the polarised light emitted from the M87 black hole, visible as beautiful spirals moving towards the event horizon. The polarisation of light around a black hole is dependent on the magnetic field surrounding it. From this added detail, scientists were able to infer that the M87’s magnetic field is between 1 and 30 gauss (50 times stronger than that of Earth’s poles) and that it is ordered, rather than scrambled, and therefore able to launch the jets of matter typically seen shooting out of supermassive black holes. This is a massive clue for astrophysicists. No one knows how these jets work, but scientists have hypothesised that they might be propelled and formed by strong magnetic fields. As the EHT team continues to update their findings, each set of images brings us closer to the inner workings of a black hole’s jet than ever before.

Left. The artist reimagines the black hole and its emanating light in the form of Bathala: the supreme deity of indigenous Filipinos. © 2024 Miko Tiu-Laurel

The first direct image of a black hole and its shadow, published in 2019 (above). Since then, images of the supermassive black hole in the M87 galaxy have been updated, showing the intense magnetic fields at the hole’s edges (below). © EHT Collaboration

Polarised light: As light moves through space, it moves as an S-shaped wave, but it is also vibrating at many different angles. However, polarised light is light that has been passed through a filter, so that it only vibrates at one angle.