Fresh photographs of Milky Way’s black hole Sgr A* reveal strong, twisted magnetic field similar to M87*

Remember that jaw-dropping first-ever image of the supermassive black hole at our galaxy’s centre, which captivated the world's attention in 2022? Well, buckle up, scientists have just unveiled an updated version of this cosmic marvel!

Dubbed Sagittarius A** (Sgr A*), this colossal black hole resides at the heart of the Milky Way, approximately 27,000 light-years away from our planet. Its image has been captured by the Event Horizon Telescope (EHT) collaboration, which includes researchers from the Centre for Astrophysics | Harvard & Smithsonian (CfA).

A polarised peek into Sagittarius A*

For the first time now, Sgr A* has been observed in polarised light, offering a fresh glimpse into its magnetic environment. The latest portrayal showcases a strong, twisted and systematically organised magnetic field enveloping the black hole.

To unlock the mysteries surrounding Sgr A*, researchers embarked on a quest to study it in polarised light. Light, an oscillating electromagnetic wave, can exhibit a preferred orientation known as “polarisation”. Although imperceptible to the human eye, polarised light offers invaluable insights into celestial phenomena.

“By imaging polarised light from hot glowing gas near black holes, we are directly inferring the structure and strength of the magnetic fields that thread the flow of gas and matter that the black hole feeds on and ejects,” said Harvard Black Hole Initiative Fellow and project co-lead Angelo Ricarte.

“Polarised light teaches us a lot more about the astrophysics, the properties of the gas, and mechanisms that take place as a black hole feeds.”

Comparing cosmic monsters

In 2019, scientists captured the first-ever image of a black hole named M87*, located at the centre of the galaxy M87,, using the Event Horizon Telescope.

Sgr A* is a thousand times smaller and less massive than its counterpart in the M87 galaxy, the blackhole M87*. However, the two black holes bear a striking resemblance. This intriguing similarity between the two cosmic cousins prompted scientists to delve deeper into their shared characteristics, particularly beyond their visual likeness.

The polarised images of Sgr A* also reveal a remarkable resemblance to those of M87*, indicating a commonality in their magnetic field structures. This revelation underscores the pivotal role of strong and orderly magnetic fields in shaping the interactions of black holes with their surrounding environment.

Prior investigations into M87* had unveiled how its magnetic fields facilitated the ejection of powerful jets of material into space. Building upon this groundwork, the latest findings suggest a similar mechanism may operate around Sgr A*.

Excitement abounds among scientists as they now possess polarised light images of both supermassive black holes. These images, accompanied by rich datasets, offer unprecedented opportunities to compare and contrast black holes of varying sizes and masses. As technology advances, these cosmic portraits are poised to unveil even more secrets, shedding light on the enigmatic nature of these cosmic behemoths.

The results were published in The Astrophysical Journal Letters and can be accessed here.