A global effort of astronomers along with ground-based and space telescopes captured the first-ever image of a black hole. You’re looking at a bright ring of light bent by the immense gravity of a black hole as it approaches (but doesn’t enter) the event horizon. The ‘hole’ we see is actually the black hole’s shadow according to the astronomers announcing today’s historic news.
I’ll let the chair of the Event Horizon Telescope (EHT) Science Council Heino Falcke explain:
“If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before. This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and allowed us to measure the enormous mass of M87’s black hole.”
M87’s black hole sits 55 million light-years from Earth and has a mass 6.5 billion times of our Sun.
How can they tell the mass? Once the team had the image above they compared it with computer models they had run. These models included everything from what the physics of warped space should look like down to the magnetic fields.
“Many of the features of the observed image match our theoretical understanding surprisingly well,” said Paul T.P. Ho, a member of the EHT Board and Director of the East Asian Observatory. “This makes us confident about the interpretation of our observations including our estimation of the black hole’s mass.”
Today’s achievement can’t be understated. This image wasn’t expected to be captured until we built even better telescopes. So how did astronomers manage to do it? They used an observation technique called very-long-baseline interferometry (VLBI). I recently wrote about how astronomers used optical interferometry to observe an exoplanet directly. It’s similar except VLBI uses radio telescopes instead of optical.
The team of astronomers used telescopes from Hawaii to Antarctica. From Arizona to the Chilean Atacama Desert. Eight ground-based telescopes from around the world were synchronized to create one giant telescope with an angular resolution of 20 micro-arcseconds. That’s a fancy way of saying it has unbelievable resolution capabilities.
The EHT press release says the combined power could let you read a newspaper in New York from a cafe in Paris. And the resolution will only get better as more telescopes join future observations.
M87’s black hole wasn’t the only one the astronomers looked at. They also peered towards the center of our own Milky Way to capture an image of Sagittarius A*. But imaging the enormous black hole at the center of the Milky Way proved a bit more difficult than M87’s. The image of Sagittarius A* will be released soon, but don’t expect the image to look much better than the one above. While Sagittarius A* is much closer, it’s also much smaller than the black hole at the center of M87.
As for M87’s black hole? There’s still plenty of questions. How far does its event horizon extend for one? That’s going to depend on how fast the black hole is spinning and how we are looking at it.
Today’s image is only the beginning and will pave the way for more research into black holes and their event horizons. We’ll keep you updated as soon as the team releases the image of our galaxy’s black hole.