British astronomers help unveil first image of black hole at centre of our galaxy

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The first image of Sgr A*, the supermassive black hole at the centre of our galaxy. Credit: EHT collaboration

Two British astronomers have helped bring to life the first image of the black hole at the centre of our own galaxy, the Milky Way.

The image provides the first direct visual evidence that the object known as Sagittarius A* (Sgr A*) is indeed a black hole.

It also yields valuable clues about the workings of such giants, which are thought to reside at the centre of most galaxies.

The two UK astronomers who are part of an international team who have made the Sgr A* observation a success are Dr Ziri Younsi from UCL and Professor Derek Ward-Thompson from the University of Central Lancashire.

Dr Ziri Younsi has helped run many black hole simulations over five years of rigorous image analysis and is the author of one of only two codes used to generate an entire library of roughly 1.8 million simulated images used for comparison with Sgr A* observations. He has recently been appointed to the EHT Science Council.

Professor Derek Ward-Thompson from the University of Central Lancashire has been named as the chair of the EHT publication committee. He is the communicating author for the six research papers that are to be published as a result of the findings.

The image was produced with the help of an international research team called the Event Horizon Telescope (EHT) collaboration, using observations from a worldwide network of radio telescopes.

It’s the first direct visual evidence of the presence of this black hole. It was captured by the EHT, an array which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope.

The telescope is named after the event horizon, the boundary of the black hole beyond which no light can escape.   Although we cannot see the event horizon itself, because it cannot emit light, glowing gas orbiting around the black hole 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.

The image of the Sgr A black hole is an average of the different images the EHT Collaboration has extracted from its 2017 observations.  In addition to other facilities, the EHT network of radio observatories that made this image possible includes the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX) in the Atacama Desert in Chile, co-owned and co-operated by ESO is a partner on behalf of its member states in Europe.

Engineers and technicians from STFC have had a valuable role in supporting the infrastructure for some of the observatories making up the EHT collaboration, including:

  • ALMA
  • James Clerk Maxwell Telescope (JCMT).

Professor Mark Thomson, STFC Executive Chair, said:

The possibility of a supermassive black hole located at the centre of the Milky Way has long captured the imagination of a global community of astronomers. With this new image of Sgr A*, we are one step closer to unravelling the mystery around the very centre our own galaxy and its surroundings.

Over the past three decades, the UK has enabled ground-breaking astronomical observations. Our role in building or maintaining some of the largest radio observatories in the world, JCMT and ALMA, has laid the foundations for the pivotal work of the EHT Collaboration.

Coupled with STFC’s continued support of UK astronomers to utilise these world-class facilities, the UK remains a key player on the global astronomy scene.

Dr Younsi, the UK Research and Innovation Stephen Hawking fellow at the UCL Mullard Space Science Laboratory, said:

Our results are the strongest evidence to date that a black hole resides at the centre of our galaxy. 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.

Producing this image is the result of a monumental effort by hundreds of scientists over five years. It was especially challenging because of the haze of stars, dust, and gas in between Earth and the galactic centre, as well as the fact that the pattern of light from Sgr A* changes quickly, over the course of minutes.

But now we have comprehensive findings, and this work opens a new chapter in our understanding of black holes.

Professor Ward-Thompson added:

The publication of the EHT picture of the Sgr A* black hole is a tremendously exciting achievement by the collaboration.

The University of Central Lancashire has been associated with the JCMT in Hawaii for over 30 years, and the JCMT is a core part of the world-wide network of telescopes that has taken this picture.


Source: UK Research and Innovation.

Launched in April 2018, UKRI is a non-departmental public body sponsored by the Department for Business, Energy and Industrial Strategy (BEIS). They bring together the seven disciplinary research councils, Research England, which is responsible for supporting research and knowledge exchange at higher education institutions in England, and the UK’s innovation agency, Innovate UK. For more details go to: https://www.ukri.org/

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