Yesterday was a big day in science in general and astronomy in particular. If you didn’t already hear the news, scientists have released their first picture of a black hole, ever. They have been detected from time to time but this is the first time one has been visualized. Previously, several black holes have been detected based on jets of material radiating from their center in X-ray light or by the ripples made in the fabric of time.
A supermassive black hole that lies at the centre of the Messier 87 galaxy within the Virgo galaxy cluster some 55 million light years away from the Earth was the subject of this study. Messier 87 is a supergiant elliptical galaxy that is one of the most massive galaxies in the local universe with approximately 12,000 globular clusters as opposed to 150-200 orbiting in the Milky Way. This black hole, named M87, is determined to have a mass that is 6.5 billion times that of our Sun.
This was accomplished by the collaboration of a team of over 200 scientists and their radio telescopes spread out around the world. The Event Horizon Telescope links together telescopes using the technique of very-long-baseline-interferometry (VLBI). VLBI uses the information gathered from these multiple telescopes and atomic time keepers to be combined to emulate a much larger telescope. (This is good because to see this black hole with a single telescope, it would have to have a dish as large as Earth itself. Not very practical.)
How is this even possible when a black hole, by its very nature, is invisible due to its immense density and gravitational field? The photograph does not capture the black hole or its interior, it captures the shadow of the event horizon (that point of no return at the boundary of a black hole.) The black hole resembles a ring of fire (no, not the Johnny Cash kind of ring of fire) surrounding a black ball. The surrounding “fire” is known as an accretion disc and is formed when gases pass over the event horizon, heat up and glow.
Up until this photograph, black holes remained theoretical. Many astronomers have been studying them for decades but there have also been many who did not believe they actually existed. Albert Einstein described gravity as a distortion of space and time within his general-relativity equations. Following in his footsteps Karl Schwarzschild took this idea and proposed the idea that matter could become squeezed into a tiny point of infinite density; a point known as a singularity. The singularity had the power to warp space around it creating a hole where nothing could escape its pull. Einstein did not immediately agree with assertion but the evidence began to pile up from the 1930s on. His theories led to the discovery of black holes but it will take more information to conclusively say whether the rules of relativity apply here.
So far, the discovery has been as predicted but it may be more interesting if they found out something that deviated from the theory. This will probably be the first of many images released and research continues.
–Janice Willson
You can check out this video for more information: https://www.youtube.com/watch?v=lxBR6RdyZAk
