Astronomers trace the magnetic field of the supermassive black hole at the center of our galaxy

Artist's impression of the magnetic field present around the event horizon of Sgr A*(Credit: M. Weiss/CfA)

A team of astronomers has successfully detected magnetic fields present around the event horizon of the supermassive black hole at the centre of our galaxy. It is thought that these magnetic fields are the driving factor behind a mechanism that sends intense pulses of galaxy sculpting radiation blasting thousands of light-years into space from the event horizon of a spinning black hole.

Known as Sagittarius A-star (Sgr A*), the supermassive black hole that sits at the heart of the Milky Way is a true monster by any standards. It is believed to be incredibly dense, compressing a mass the equivalent of four million times that of our Sun into a space no larger than the planet Mercury.

Sgr A* sits roughly 25,000 light-years from Earth, a distance which, when combined with the black hole's relatively diminutive size, would necessitate a telescope of prodigious size in order to capture the phenomenon. Thankfully, we just so happen to have one on hand.

The recent observations were made using the Event Horizon Telescope (EHT), a colossal virtual telescope that spans the entire globe. The EHT is made up of many individual radio observatories, which when combined will grant the EHT a resolution of 15 arc seconds, the equivalent of a thousand times the resolution of the Hubble Space Telescope.

Using the EHT, the team was able to trace the shape of Sgr A*'s magnetic field by measuring how light from the black hole is linearly polarized as it spirals around magnetic field lines. The observations showed that sections of the magnetic field lines were tangled, looping and chaotic, whereas others appeared to assume a more organized structure.

Furthermore, the characteristics of the black hole itself made the magnetic field easier to characterize, with the gravity from Sgr A* magnifying the light to make it roughly five times larger when viewed from Earth, placing it within the observational capabilities of the EHT.

The team believes that the more stable sections are where the powerful jets of radiation eminate from. The end result of the observation essentially grants evidential grounding to previous theories on the relationship between the jets and the magnetic field that sits just outside Sgr A*'s event horizon.

A paper on the discovery has been published in the online journal Science.


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