On April 10, 2019, astronomers released the first-ever image of a black hole. This image depicts a supermassive black hole in the center of a giant elliptical galaxy known as M87. This image is incredibly important because black holes have never been seen before because they’re, well, black. Black holes do not emit any light (like stars do), nor do they reflect light (light the moon does). This makes them notoriously difficult to detect. In fact, black holes were purely theoretical until the detection of gravitational waves in 2015.
What Are Black Holes?
Black holes were first theorized in the 18th century, but they weren’t truly predicted until 1915 when Einstein published his theory of general relativity. Black holes are a natural prediction of this theory, which simply states that mass bends the four-dimensional spacetime. Not long after, Karl Schwarzschild solved Einstein’s equations and found that for an infinitesimally small point mass, the equations break down when you get near the point mass. This means that physics stops working once you get too close to a black hole. The distance at which physics breaks down is known as the Schwarzschild radius. This radius forms a spherical surface known as the event horizon.
Black holes are an example of extreme physics that form after a massive star dies. This star collapses in on itself and doesn’t stop until the mass is concentrated at an infinitesimally small point in space. This forms a gravitational well so deep that nothing—not even light—can escape. This has one main consequence: we can’t see black holes. What’s more, there didn’t seem to be any way that we could even prove they existed. However, in 2015, scientists had the first physical proof of black holes via gravitational waves. Gravitational waves radiate from high energy collisions. Detectors found evidence of such a collision between two supermassive black holes. Now, for the first time ever, we see a black hole.
Seeing Black Holes
The image shows the black hole in the center of M87, a massive elliptical galaxy. Scientists knew that this galaxy contained an active black hole because of the blue jet seen in the image below.
Scientists used a collaboration of radio telescopes across the globe to see the black hole. They took so much data from their observations that it couldn’t be shared over the internet; they had to manually take the hard drives to one location. After observing the black hole in 2017, it took them two years to compile the data into a single image.
When looking at the image released by the New Horizons Telescope, seen below, one can see a red ring around a dark center. This dark center is the event horizon of the black hole—the point of no return. The red ring is hot, energized, glowing gas. This gas is glowing because it is being flung around the black hole, heating it up. Furthermore, the gas is brighter at the bottom of the image because there, the gas that is moving towards us.
Even today, there are tons that we don’t know about black holes. We don’t know how the supermassive black holes in the center of galaxies formed. We don’t know what happens to the information pulled into black holes. We don’t even know how many black holes there are. To say the least, there is a lot of research about black holes coming. Who knows what secrets they keep to themselves. Maybe one day, we’ll find out. Until that day, astronomers will keep on searching the stars for answers.
madison brewer 