Image: EHT Collaboration.
Due to its distance from us, imaging this behemoth of a black hole is enormously challenging. It requires a resolution sharp enough to focus on an orange on the surface of the Moon, or being able to see individual atoms in one’s own finger. The telescope managed this thanks to an unprecedented collaboration between scientists across the globe, linking together eight ground-based radio telescopes and transforming the Earth into one giant virtual radio telescope.

Black holes are perhaps the most enigmatic objects in nature, powering some of the most energetic – and unobservable – phenomena in our universe. Due to their event horizon, the boundary beyond which nothing, not even light, can escape, we cannot see a black hole directly. But matter that falls towards a black hole is drawn in by its immense gravitational pull and becomes extremely hot and luminous.

As it approaches the event horizon, this matter is super heated by friction and moves close to the speed of light, emitting copious amounts of radiation. It is radiation in the form of radio waves produced by this gas moments before it crosses the event horizon that the telescope is designed to detect.

Our observations provide new, detailed information about the structure of the magnetic fields just outside the black hole. Not only does this bring us a step closer to understanding how these mysterious and powerful jets are produced, it also explains how some ultra hot matter can lurk outside a black hole, resisting its gravity. Our research suggests that the magnetic fields are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can start flowing inwards to the event horizon.

As exciting as these new polarised images of M87’s black hole are, it is still only the beginning for the EHT collaboration and the science of black hole imaging. We are already working on what the image of the black hole that resides in the centre of our own galaxy would look like, which we hope to publish later this year. This is Sagittarius A*, or Sgr A*, our galaxy’s supermassive black hole.