This week, the world of astronomy has been abuzz with news of the very first supermassive black hole image. The supermassive black hole is located 55 million light-years away at the center of M87, a neighboring supergiant elliptical galaxy in the constellation Virgo. The object itself has a diameter of 24 billion miles, and is an incredible 6.5 billion times more massive than the Sun.
The photograph was made possible by the Event Horizon Telescope, which will now also be used to observe many other kinds of astronomical objects beyond black holes. Commenting on the historic development, EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian, stated:
“We have achieved something presumed to be impossible just a generation ago. Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.”
Event Horizon Telescope Project
The remarkable supermassive black hole photograph is the culmination of the Event Horizon Telescope (EHT) project, which involved a team of more than 200 researchers. From their international locations, they then used eight powerful telescopes to form an Earth-sized virtual telescope with unprecedented levels of sensitivity and resolution. These locations included Hawaii, Mexico, Arizona, the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.
“To make sure these observations were truly simultaneous, so that we could see the same wavefront of light as it landed on each telescope, we used extremely precise atomic clocks at each of the telescopes,” explained Daniel Marrone, associate professor of astronomy at the University of Arizona.
Supermassive Black Hole Image
Back in April 2017, the telescope array collated 5,000 trillion bytes of data over a two week period, with supercomputers then processing the data to produce the black hole image. The results were subsequently only revealed on 10 April 2019.
The image has a distinctive donut shape, with the supermassive black hole shown surrounded by hot swirling gas. It is also provides the only direct visual evidence of the existence of these dense points in space. The supermassive black hole at the center of M87 has since been named Powehi, which refers to a Hawaiian phrase meaning an “embellished dark source of unending creation”.
Why Not Image The Milky Way’s Black Hole?
The black hole image was taken at a distance of 55 million light-years away, but our own Milky Way galaxy has a supermassive black hole called Sagittarius A* located around 25,640 light-years away. So wouldn’t it have been easier to have photographed Sagittarius A* instead?
Quite simply no. This is because our Milky Way’s black hole appears side on from Earth’s location, which is then obscured further by all the stars, planets, gas, and dust in the way. The image taken of Powehi, however, shows the supermassive black hole head on. It is also much bigger than our own Milky Way’s black hole. For example, Sagittarius A* has a diameter of 44 million km and 4 million solar masses versus Powehi, which has a diameter of 24 billion miles and 6.5 billion solar masses.