Say cheese: black hole to shed light on Milky Way
Scientists capture first image of supermassive collapsed star that anchors Earth’s home galaxy
THE supermassive black hole at the centre of the Milky Way has been pictured for the first time by astronomers.
Sagittarius A* is an enormous black hole anchoring Earth’s galaxy, serving as the fulcrum around which the spiral arms rotate.
Astronomers at the Event Horizon Telescope (EHT) project have revealed the image of the black hole, three years after they published the first image of any black hole.
In 2019, the image of the black hole Messier 87* 55 million light-years away made headlines worldwide, and now the team has focused the telescope on Earth’s celestial back garden.
Black holes – the remnants of stars that have died in a supernova explosion and collapsed in on themselves – are incredibly dense. Their gravitational pull is so strong that it sucks in everything around it, including light.
As a result, they can not be imaged directly, but light that has been distorted by the gravity can be picked up.
Analysis found the black hole, which is 27,000 lightyears away from Earth, is four million times larger than our Sun.
Dr Sara Issaoun, an EHT astronomer, said: “We measure the size of the shadow of Sagittarius A* to be 52 micro arc seconds in the sky – this is about the size of a doughnut on the surface of the moon as seen from Earth. In reality, Sagittarius A* is about as big as the orbit of Mercury around the Sun.”
Feryal Ozel, an astrophysicist at the University of Arizona, described the black hole as “the gentle giant in the centre of our galaxy”.
Yesterday, the EHT team said the black hole is orientated “face on” towards Earth, making it extremely difficult to detect if there is a jet of activity expelling particles from the centre of the black hole as, if it exists, it would be pointing directly at our planet.
Photographing this black hole was much trickier than the watershed moment of Messier 87*, researchers said, because of rapidly moving gas obscuring the shot. Experts likened the process to “trying to take a clear picture of a puppy quickly chasing its tail”.
Dr Benjamin Pope, a University of Queensland astronomer, called the observations “an extraordinary tour de force technically”. Applauding the results of the first EHT images of Messier 87*, he added: “Sagittarius A* is a moving target, and it required even more ingenuity in maths and software to develop today’s time-lapse exposure of this flickering disk.”
Dr Ziri Younsi, a UCL astronomer and EHT Collaboration member who coauthored the findings’ research paper, said: “This black hole is the glue that holds the galaxy together. It is key to our understanding of how the Milky Way formed and will evolve in the future.”
Prof Sera Markoff, co-chairman of the EHT Science Council based at the University of Amsterdam, said that now there were images of both Sagittarius A* and Messier 87*, the team could learn more about black hole formation.
“We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar,” she said. “This tells us that general relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes.”
The findings were published in a special issue of The Astrophysical Journal Letters.