Why Does The First Black Hole Picture Have An Orange Ring In It?

On the 10^th of April, we have our first chance ever to see a black hole, thanks to the effort of more than 200 astronomers. What the picture shows is an orange ring around a black core in the middle. The object of the photo is at the center of the galaxy Messier 87, about 55 million light-years from Earth. However, many wonder why the black hole takes the shape of a giant ring, so here is the answer.

A black hole is extremely large; the particular one we see in the picture has the mass that is 6.5 billion times bigger than that of our Sun. Their enormous size gives them the ability to bend spacetime. Any gas or dust around them is heated up to an extremely high temperature.

Technically, we cannot see a black hole because they let no light out. However, Albert Einstein once said that in some cases, human could see their outlines.  If the black hole is immersed in a bright area, it can result in something that resembles a shadow. The M87’s black hole is not the nearest scientist can find, but since it is extremely large, it is easier for the EHT to work on it.

This explanation tells us why we see an orange ring around a black core. What the circle has inside of it is the shadow that the black hole creates while the ring itself is the glowing environment needed to make it visible.  However, orange is not the actual color of that zone but rather what EHT picked to represent how bright the surrounding area is. The black color means there is no light at all, red is medium, while orange indicates the most intense brightness.

If we compare the ring with the optical range, the ring will probably look like it is white with a little bit of red or blue.