‘A view of the M87 black hole in polarised light’ by EHT Collaboration
Katie Bouman HonFRPS is renowned for helping to create the first image of a black hole.
The recipient of the RPS Progress Medal 2021 was part of the Event Horizon Telescope (EHT) collaboration which visualised the black hole at the centre of Galaxy M87, 55 million light years away.
Bouman, at the time a 29-year-old PhD student, was one of more than 200 researchers at multiple universities worldwide involved in this astonishing achievement in image-making.
Eight telescopes around the globe had been used to create a virtual Earth-sized telescope to observe the core of the M87 galaxy. But it was the expertise in algorithms of Bouman and her colleagues at Harvard University that crucially helped fill in gaps in the data.
Bouman, who is now assistant professor of computing and mathematical sciences, electrical engineering and astronomy at Caltech, told the RPS Journal: “Just as your brain may be able to recognise a song being played on a broken piano if there’s enough functioning keys, we can design algorithms to intelligently fill in the EHT’s missing information and reveal the underlying black hole image.”
The first image of the black hole was finally released to the public on 10 April 2019. It shows a bright, ring-like structure with a dark central area. Since then, the EHT has shown the light circling the M87 black hole in a different dimension.
The image shown at the top of this page, first published by the EHT collaboration in March 2021, reveals that a significant fraction of the light around the M87 black hole is polarised – meaning it vibrates in only one direction. Bouman helped develop the imaging tools used to create the image in a project led by Monika Moscibrodzka and Ivan Marti-Vidal.
“The lines mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole,” explains Bouman. “It is important to realise the ridges in the image do not physically exist around the black hole – they are simply a representation of another dimension of light (polarisation) that we cannot see with our own eyes.”
An EHT video explains: “Black holes are enveloped in plasma. This plasma has magnetic fields – areas where magnetism affects how matter moves – threaded throughout. As the magnetic field grows stronger, it changes shape and the polarised light we measure exhibits different patterns.”
Katie Bouman discusses scientific images that have inspired her in her acceptance speech for the RPS Progress Medal 2021.
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