On April 10, 2019, like millions of others, I was eagerly awaiting the release of the picture of one of the extreme objects in the universe. It is a picture of a region in space where gravity is enormous enough to trap all of matter if it was close enough. Even light isn’t shown any mercy. Yes, we are talking about black holes. And who doesn’t love a black hole?
Space subject
The recently released photo of the black hole caused much excitement around the world because a black hole had never been seen before. The target object, the supermassive black hole in the centre of giant galaxy M87 is 6.5 billion times the mass of the sun, and is 55 million light years away. When viewed from Earth it is so small.
Lighting up for the camera
An image of something that traps even light? That’s absurd. How can we see something that is in essence just a ‘black hole’? What we actually see is the black hole’s silhouette. We are observing almost the boundary of a black hole beyond which point there is no return for both light and matter. It is called the Event Horizon. To observe such a boundary, the black hole needs to be illuminated. The source of illumination here is called accretion disk, which comprises dusts that are spiralling into the black hole. Yes, black holes devour anything that fall into its web: the event horizon. As they fall in, there is a huge amounts of friction that heats up the gases to several million degrees, and particles are moving at tremendous speeds (fraction of speed of light).
The challenge
Since there is stupendous amount of gravity, a black hole bends spacetime so much that light (in this case 1.3 mm radio waves) from the accretion disk are bent around as they travel near the black hole and continue its journey towards us (the telescopes), which is collected as data and processed later.
As Katie Bouman, the computer scientist, who led the development of an algorithm for imaging black holes said in a TED talk, looking (from Earth) for this particular supermassive black hole at the centre of a galaxy is like looking for an orange on the surface of the moon. And to look at the orange on the surface of the moon, telescopes needs to be really powerful. For telescopes to be more powerful they need to be bigger. And when the size of the telescope to spot the orange on the moon was calculated, it turned to be as big as Earth itself, a physical impossibility.
How the photo came to be...
The project was commissioned by the Event Horizon Telescope project in 2009.
It comprised more than 200 scientists across different disciplines.
It used eight giant radio telescopes across the planet, which when put together mimic one giant telescope using a technique called interferometry.
The data collected by all the telescopes not only covered the target black hole, but had a lot of unwanted data as well (noise).
The data was also sparse because there were no telescopes in all parts of the world and neither could the entire world be made into one giant telescope as previously stated. The gaps in data needed to filled in later using computer algorithms
Bouman and her team led the development of an algorithm which she named CHIRP (Continuous High resolution Image Reconstruction using Patch priors).
The algorithm was responsible for stitching together data from all the telescopes and filling in the gaps.
The output: the black hole image!
In the spotlight
Screenshot of Katie Bouman from a TED Talk
As soon as the picture of the black hole was released, Katie Bouman was the name mentioned everywhere.
Bouman is a postdoctoral fellow with the Event Horizon Telescope and will soon be joining as an Assistant Professor in the Computing and Mathematical Sciences department at California Institute of Technology, Pasadena, California, the U.S., this year.
She was interested in imaging research right from when she was young, and she came to know about the Event Horizon Telescope project in 2007.
She graduated from high school the same year. She was already doing imaging research in Purdue University where her father was a professor.
She is an exemplary example of what humans are capable of. The story of Katie Bouman is inspiring.
Thank you, Katie Bouman, for enabling us to see a black hole!
The writer is a Science Educator and Communicator at Mango Education.
