Free Astronomy Magazine July-August 2024

23 JULY-AUGUST 2024 ASTRO PUBLISHING I n 2022 scientists un- veiled the first image of Sgr A* at press con- ferences around the world, including at the European Southern Ob- servatory (ESO). While the Milky Way’s super- massive black hole, which is roughly 27,000 light-years away from Earth, is more than a thousand times smaller and less massive than M87’s, the first-ever black hole imaged, the observations revealed that the two look re- markably similar. This made scientists won- der whether the two shared common traits outside of their looks. To find out, the team decided to study Sgr A* in polarised light. Pre- vious studies of light around the M87 black hole (M87*) revealed that the magnetic fields around it allowed the black hole to launch powerful jets of material back into the surrounding environment. Build- ing on this work, the new images have revealed that the same may be true for Sgr A*. “What we’re seeing now is that there are strong, twisted, and or- ganised magnetic fields near the black hole at the centre of the Milky Way galaxy,” said Sara Issaoun, NASA Hubble Fellowship Program Einstein Fellow at the Center for As- trophysics | Harvard & Smithsonian, US, and co-lead of the project. “Along with Sgr A* having a strik- ingly similar polarisation structure to that seen in the much larger and more powerful M87* black hole, we’ve learned that strong and or- dered magnetic fields are critical to how black holes interact with the gas and matter around them.” T he Event Horizon Telescope (EHT) collaboration, who produced the first ever image of our Milky Way black hole released in 2022, has captured a new view of the massive object at the centre of our Galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a sig- nature of magnetic fields, this close to the edge of Sagittarius A*. This image shows the polarised view of the Milky Way black hole. The lines overlaid on this image mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole. [EHT Collaboration] T his visible light wide-field view shows the rich star clouds in the constellation of Sagittarius (the Archer) in the direction of the centre of our Milky Way galaxy. The entire image is filled with vast num- bers of stars — but far more remain hidden behind clouds of dust and are only revealed in infrared im- ages. This view was created from photographs in red and blue light and form part of the Digitized Sky Sur- vey 2. The field of view is approximately 3.5 degrees x 3.6 degrees. [ESO and DSS 2. Ack.: Davide De Mar- tin and S. Guisard (www.eso.org/~sguisard )]