The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration. The image is presented today by EHT Director Huib Jan van Langevelde (JIVE/Leiden University) on a press conference in the European Southern Observatory (ESO) headquarters in Germany.
The team has made use of observations from a worldwide network of radio telescopes. In the Netherlands, astronomers and technicians from University of Amsterdam, Radboud University, Leiden University, University of Groningen, JIVE and ASTRON are part of the EHT collaboration. The EHT team's results are being published today in a special issue of The Astrophysical Journal Letters.
First evidence of Sagittarius A*
The image is a long-anticipated look at the massive object that sits at the very centre of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the centre of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced "sadge-ay-star") — is a black hole, and today’s image provides the first direct visual evidence of it.
Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.
“We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity," said EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. "These unprecedented observations have greatly improved our understanding of what happens at the very centre of our galaxy, and offer new insights on how these giant black holes interact with their surroundings.”