Photographing a black hole and the increase in collaboration within science

Humankind has the innate tendency to be fascinated with the unobservable. With modern equipment and machinery, we have been able to observe and look at some of the most astronomical events that happen in the universe. Be it Supernovae, or star birth or the signs of the big bang, modern advancements have allowed us to observe these first hand, as they happen. But how do you observe something that has been cloaked away by nature, completely invisible, like a delicate embryo in a womb? That was answered in 2019 by a team of some of the most brilliant scientists of the 21st century. To understand how, let’s look at what a black hole is precisely.

When a start crosses the Chandrashekar Limit, which is the limit at which the pressure inside the core of star can longer support its own gravitational pull for itself, the star collapses upon itself, compressing all of that mass into a very small region, to form either a neutron star or, you may have guessed it, a black hole. The first “real” prediction of a black hole came in 1916 when Albert Einstein discovered that an object of infinite mass could, quite literally, “puncture” spacetime. I say puncture because Einstein imagined space and time to be a continuous fabric, like cloth. Mass, when introduced to this fabric, could bend it and in return, this fabric would tell mass how to move. A very mutual relationship.

When lots and lots and lots of mass, like that of a black hole interacted with space-time, the bend became more of a hole, which is why the term “black hole” was first used. Now that we have a clear definition of how spacetime behaves when interacting with a black hole, we can investigate the first problem. When we want to photograph something on Earth, we depend on light entering the lens.

Black holes reflect no light.

Black holes have such an immense gravitational pull that light bends, quite literally, inside them. They give off no light off their own so how would we ever think of photographing something like this? Well, we compromised. We did not exactly capture the black hole- instead, we photographed its silhouette-outlined by the glowing gas that surrounds its event horizon, the precipice beyond which light cannot escape. It’s the gas and dust that circles the black hole, known as the accretion disk. The second task was how to approach this task. It was theorized that we’d need a telescope the size of the Earth which is, erm, not possible. Instead, again, we compromised. We built a network of telescopes around the globe synchronized by an atomic clock known as the Event Horizon Telescope (EHT). They set out to capture an image of a black hole by improving upon a technique that allows for the imaging of far-away objects, known as Very Long Baseline Interferometry, or VLBI.

Telescopes of all types are used to see distant objects. The larger the diameter, or aperture, of the telescope, the greater its ability to gather more light and the higher its resolution (or ability to image fine details). To see details in objects that are far away and appear small and dim from Earth, we need to gather as much light as possible with very high resolution, so we need to use a telescope with a large aperture.

That’s why the VLBI technique was essential to capturing the black hole image. VLBI works by creating an array of smaller telescopes that can be synchronized to focus on the same object at the same time and act as a giant virtual telescope. In some cases, the smaller telescopes are also an array of multiple telescopes. This technique has been used to track spacecraft and to image distant cosmic radio sources, such as quasars.

The closest supermassive black hole to Earth, Sagittarius A, interested the team because it is in our galactic backyard – at the center of our Milky Way galaxy, 26,000 light-years (156 quadrillion miles) away. Though not the only black hole in our galaxy, it is the black hole that appears largest from Earth. But its location in the same galaxy as Earth meant the team would have to look through “pollution” caused by stars and dust to image it, meaning there would be more data to filter out when processing the image. Nevertheless, because of the black hole’s local interest and relatively large size, the EHT team chose Sagittarius A as one of its two targets.

The second target was the supermassive black hole M87. One of the largest known supermassive black holes, M87* is located at the center of the gargantuan elliptical galaxy Messier 87, or M87, 53 million light-years (318 quintillion miles) away. Substantially more massive than Sagittarius A, which contains 4 million solar masses, M87 contains 6.5 billion solar masses. One solar mass is equivalent to the mass of our Sun, approximately 2x10^30 kilograms. In addition to its size, M87 interested scientists because, unlike Sagittarius A, it is an active black hole, with matter falling into it and spewing out in the form of jets of particles that are accelerated to velocities near the speed of light. But its distance made it even more of a challenge to capture than the relatively local Sagittarius A. As described by Katie Bouman, a computer scientist with the EHT who led the development of one of the algorithms used to sort telescope data during the processing of the historic image, it’s akin to capturing an image of an orange on the surface of the Moon

EHT, along with several of NASA’s observatory were pointed at M87*, the primary target. We started getting data, however, what exactly were they capturing if there was no light? Thats the thing, only the light which crosses the Event Horizon (which is the point after which there is no escape from the pull of gravity) is unreachable, however a lot of light which is bent by a black hole is still “seeable”, something like this:

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And now we run to our third and final problem- our data was incomplete. The data that we get from astronomical objects so far away pass through solar dust, radiation, and a bunch of other things that put fracture the already small amount of data. Not to mention, light travelling through such a massive distance bends just a tiny, tiny, tiny bit, but still enough to give inconsistencies.

This problem was countered with the modern computer imaging technique called Interferometry. I will present Katie Bouman’s explanation on it and recommend the associated video:

Watching the black hole with the Event Horizon Telescope (EHT) is a bit like listening to a song that is played on a piano that has a lot of broken keys. If we had telescopes located everywhere on the globe we would be able to hear all possible notes, and thus hear a perfect rendition of the song. However, as the EHT only has telescopes at a few locations, we must recognize the song being played with just a few notes. Although hearing a song being played this way is definitely not perfect, a lot of times there is still enough information to follow along.
To make this a bit more clear, listen to the song in this video (use headphones for the best experience). In the video we play a song as if we were increasing the number of telescopes in the EHT, essentially fixing the broken piano keys. At the beginning you are going to hear only one note of this song, and as you go on you are hear more and more notes until eventually you will start to be able to make out a (hopefully familiar) song. The notes corresponding to the tones we are currently playing on the piano keyboard will be lit up so you can see what you are hearing.
By close to the end, even before all the notes were playing, you may have been able to start to recognize the song - Vanilla Ice’s Ice Ice Baby - and even if you don’t know the song you probably were still starting to get the gist of it. Even though near the end there were still a lot of gaps in the notes that were playing, it’s pretty amazing that your brain can fill in holes and you can start to make out the song. What your brain was doing here is very similar to what the imaging algorithms that we develop for the EHT do. Using the sparse data we collect from the telescopes, our algorithms fill in the missing gaps with the most natural looking image.
But there is one point I want to draw your attention to: there is always some ambiguity in what the true image is. For example, even if many notes are playing, as long as there were some notes missing, it doesn’t have to be Vanilla Ice’s Ice Ice baby. The more notes missing, the more ambiguity there is. In fact, perhaps close to the beginning you may have thought that the song was Queen and David Bowie’s song Under Pressure rather than Vanilla Ice’s Ice Ice Baby. If those were the only notes we heard we would be in trouble, as there are multiple songs that fit the notes we are hearing fairly well. However, as we increased the number of notes (measurements) this possibility eventually disappeared.

Throughout this project the common theme of scientists sharing findings, brainstorming together, discovering problems and thinking of solutions is key. Science has become a collective monster where to stand by yourself is to stand alone, literally. It is no longer possible to bridge different fields together without spending at least 10 years of active work, by which point the window for work passes.

This spike in collaboration is quite optimistic in terms of problems that we’re facing right here on our home planet. It allows us to be hopeful that while facing two of the biggest threats that we face right now, those being climate change and and efficient waste disposal, we’ll have concrete peer-review process, and the best of humanity will be countering the worst of humanity.

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Boring
This sucks I refuse to like this post do better

“In many ways, the work of a critic is easy. We risk very little, yet enjoy a position over those who offer up their work and their selves to our judgment. We thrive on negative criticism, which is fun to write and to read. But the bitter truth we critics must face, is that in the grand scheme of things, the average piece of junk is probably more meaningful than our criticism designating it so. But there are times when a critic truly risks something, and that is in the discovery and defense of the new. The world is often unkind to new talent, new creations. The new needs friends.”

I found Claws post both informative and inspiring, a much needed quality for increasing the science literacy of those otherwise unbeknownst to the wonders of what human advancement could become, lest we surrender to the urge to disengage it.

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don’t care didn’t ask + you’re white + get critiqued loser