Tuesday, November 30, 2021
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Seeing Darkness: First Picture of the Black Hole

Figure 1: The first image of a black hole, from the galaxy Messier 87. Source: National Science Foundation
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The world has seen darkness for the first time. Since 1916, black holes have been theorized, first conceptualized by Albert Einstein in his theory of relativity. But for decades they have remained hidden and illusive, impossible to capture as they sucked the light around them with their immense gravitational pull. Observed only by their effects on their surroundings, black holes have captured the imaginations of both scientists and science fiction authors alike, even being featured in prominent movies such as Interstellar. Their nature is one shrouded in mystery, an object defying laws of physics, making this image more precious and awe inspiring.

The modern definition of a black hole was first thoroughly developed by Karl Schwarzschild, who completed Einstein’s equation. Defined as an object with almost infinite density, a black hole was a radical concept to physicists and remains an unexplored area. Black holes have three “layers” – the outer and inner event horizon and the singularity. The event horizon of a black hole is the boundary around the mouth of the black hole where light loses its ability to escape. Once a particle crosses the event horizon, it cannot leave. Gravity is constant across the event horizon. The inner region of a black hole, where its mass lies, is known as its singularity, the single point in space-time where the mass of the black hole is concentrated. Virtually nothing can escape from them — under classical physics, even light is trapped by a black hole. Such a strong pull makes observation and photography impossible in the traditional manners.

However, after years of multiple attempts and hundreds of thousands of dollars on various methods, on April 10, 2019, the National Science Foundation released the world’s first image of a black hole, captured by the Event Horizon Telescope. This image physically proves the existence of black holes and solidifies the veracity of the theory of relativity.

The Event Horizon Telescope is the reason humanity can visualize this vastly theorized object for the first time. A telescope the size of the Earth is what it took to take an image of the black hole, which is 57 million light years away from Earth (3.35 x 1020 miles). A distance this large required the largest telescope humanity had access to: Earth. Using 8 separate telescope arrays from around the world and a technique called Very Long Baseline Interferometry, the Event Horizon Telescope turned Earth into one giant telescope. By using atomic clocks to align the observations in time and supercomputers to compile the petabytes of data, scientists can effectively achieve the resolution of an Earth-sized telescope—but not the light collecting capability, so the technique can only be used to observe very bright objects. VLBI can only collect radio waves on the surfaces of the dishes, which are constantly rotating with the Earth, keeping an eye on the center of M87. While the picture may not have been the original target, with the Event Horizon Telescope focused primarily on Sagittarius A* (the black hole in the center of the Milky Way), the scientific importance of this picture is unparalleled.

The first real image of a black hole, no simulations or animations, is a huge stride for humanity, affirming not only Einstein’s theories, but also the existence of black holes. And this is just the start, opening a whole new field for exploration as light is shined on the darkest object known to man.









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