What is a Black Hole?

A black hole is a great amount of matter where gravity is extremely enough that does not allow any particle or electromagnetic radiation can escape from it. It is a regional spacetime with overwhelming gravitational acceleration.

Over the past centuries, astrophysicists base their evidence about black hole on indirect observations, hypothetical data, and scientific theories. Recently, however, scientists have managed to take a photo of a black hole using the Event Horizon Telescope (EHT).

How did the scientists manage to capture the first-ever image of a black hole?

Scientists used the Event Horizon Telescope, a network of telescopes that uses Very Long Baseline Interferometry (VLBI). VLBI is a highly-sophisticated technology that allows for the imaging of faraway objects.

The scientists gathered as much light as they can gather while using high-density resolution telescope with a large aperture. The bigger the diameter of the aperture, the more light is gathered, which in turn produces higher density resolution.

The aperture of an Event Horizon Telescope is as large as the distance between the two farthest telescope stations. This is creating an aperture that is almost as big as the diameter of the Earth. 

The VLBI technique works by creating a series of smaller telescopes which can be arranged to focus on one particular object at the same time. These synchronized telescopes act as one huge virtual telescope.

The series of telescopes are focused on the target which is the black hole. Data is then gathered and collected in the different locations of the telescope, each providing a portion of the virtual telescope's full view. The more small telescopes used the better imaging can be produced.

The VLBI techniques had been widely used in tracking spacecraft and the behavior of most cosmic bodies. It is also used for imaging distant cosmic radio sources such as nebulae, quasars, pulsars, and radio galaxies.

The image of the black hole shows a fiery disc of accreted gases surrounding the black hole which is located at the core of the Messier 87 galaxy. It has a diameter of 38 billion kilometers or 23.6 million miles with an active supermassive colossus that lurks at 55 million light-years from Earth.

The imaging shows a dark area at the center of the ring that represents the shadow of the black hole. A clear view of the black hole itself is very difficult to "see," however, the gases that seemingly corresponds to the light of ring and the shadow produces the very first image of a black hole.

The image appears to be the representation of previous predictions of black holes. It shows the distortion of space and time caused by immense objects with massive gravitational acceleration.

Black hole is no longer a mere theory! The first image of the black hole says it all!