This year astronomers released the first ever groundbreaking image of a black hole. Captured within this simplistic yet impactful image is confirmation of one of the biggest and most complicated astronomical mysteries in human history. Albert Einstein produced equations to suggest that they existed and there were lines of evidence, but this is the first direct proof the first ever magnificent image and what a breakthrough it is. This black hole is a monster and one of the largest known that exists in the known universe in the past we have managed to capture bright glowing quasars and star dense galactic cores, but what sets this image apart is that not only can we see the accretion disk also known as the so-called glowing ring of fire around the edge, but we can also see this in front of the event horizon, the dark and up until now the theoretical chamber of a black hole. Beyond this barrier the gravity is so strong that nothing in the Universe can escape from it not even light hence the empty void like object we see in this image. This is the first time capturing an event horizon and this strengthens our knowledge of black holes.
Before we were unable to conclude on these massive gravity centers, not just being incredibly dense or compact neutron stars or some sort of similar object with a huge gravitational field. We only had infrared images of stars at the center of our galaxy orbiting something with an enormous gravitational pull, but because the black hole is just that, black, we couldn't actually see what was lurking in the dark independently from the black backdrop of space. Even Einstein himself was unsure whether his mathematical equations could actually correspond to such a near physics-defying object, but we now know this to be the case and black holes are indeed very real. This reassures a lot of our predictive models of astrophysics and adds visual evidence to decades of mathematical calculation and refinement. The black hole is confirmed and we can now start to speculate on some much deeper mysteries of cosmology all thanks to this one beautiful image.
So, about the black hole itself, what are we actually looking at in this image? this black hole is in the center of the super-giant elliptical galaxy Messier 87 also known as ‘Virgo A’ or ‘M87’ located over 50 million light-years away in the constellation of Virgo, hence its alternative name. A Messier object is the catalogue of 110 astronomical objects, first recorded by French astronomer Charles Messier in his catalogue of nebulae and star clusters. He was originally trying to locate comets, before identifying these objects and collaborating them into a list of non-comet objects that would help form the basis for the classification of many of our neighboring galaxies and nebulae. Initially all the Messier objects were thought to be located within our Milky Way galaxy, before Messier 31, aka the Andromeda galaxy was identified as an extra galactic object.
Virgo A is a 53 million light-years distant object and the galaxy itself is absolutely enormous. Its radius extends just under 500,000 light-years, meaning its total diameter verges on a mind-bending 1 million light-years across. This is just one of thousands of supergiant elliptical galaxies that we know of. To put that in some kind of perspective, it was recently discovered that our Milky Way galaxy is probably quite a lot larger than we initially thought. Our estimates used to sit at between 100 to 130 thousand light years across, but it is now more likely to be between 150 to 200 thousand light years, putting it nearly on par with our nearest spiral galaxy the Andromeda galaxy. Even at the upper bound of this estimate, M87 is at least 5 times larger than our home galaxy. Supermassive black holes lie at the center of galaxies and play significant role in binding them together at the central bulge. M87’s black hole is one of the most massive ever recorded, it measures 40 billion kilometers across and has a mass of over 6.5 billion solar masses so that's 6.5 billion times heavier than our own Sun.
The largest black hole ever noted TON 618, which is a very distant and radio-loud quasar estimated to weigh in at just over 10 times that mass, but make no mistake 10% of the mass of the largest black hole ever discovered is still an absolute giant of the cosmos.
What you can see in this picture is almost as large as our entire solar system, this made it large enough to be photographed, leading to this breakthrough. This black hole is an enormous size but it still sits at over 50 million light years away. So how did we manage to photograph such a distant object right here on Earth?
Photographing a black hole began with Professor Heino Falcke of Radboud University in the Netherlands. As a young PhD student in 1993 he had the idea for an initiative to capture a photograph of a black hole. Driven by the determination to see one for himself however at the time nobody thought this could be possible the idea of taking a picture of a black hole over the black backdrop of space was dismissed. That being said Falcke argued that black holes generated a certain type of radio emission which could be detectable from Earth. He also proposed that due to the gravitational field of black holes and their subsequent effect on traveling light black holes may appear around two-and-a-half times larger than they actually are when observed. These two factors in his view made the prospect a possibility. It would take years, millions of dollars and the overcoming of several scientific obstacles along the way, but they had a shot. Eventually after 20 years of arguing his case Falcke managed to persuade several astronomical bodies, mainly the European Research Council and the National Science Foundation to fund the project. Before long, space agencies in East Asia contributed funding giving the project $50 million. So that was one problem solved, but several more still lay ahead. In order to capture a black hole, you would need a radio telescope. Radio telescopes are used because of the aforementioned nature of the black hole, you can't capture a lightless object against the black backdrop of space with just visible light, but the radiation being emitted from the black hole on its accretion disk could hypothetically be illuminated when viewed with a radio telescope to act as a luminous backdrop. This allows us to photograph not only what we've already seen the ring of fire that is the glowing accretion disk, but also the event horizon itself, the dark barrier beyond which light can no longer escape. Capturing both would be an essential requirement improving the existence of black holes as we understand them. The only problem is that every supermassive black hole that we know of is unimaginably distant and to photograph them would require a telescope at least the size of Earth and obviously we can't just construct a radio satellite dish that size. but humans are clever and creative and we soon found a way around that too. Professor Shepard Doelemen of the Harvard-Smithsonian Center for Astrophysics formed an initiative to create a network of eight interlinked radio telescopes. If these were placed at strategic points around the Earth, each one's readings could be merged together to form a bigger picture taken as if the entire Earth were one big radio telescope. This laid the foundations for the Event Horizon Telescope.
The Event Horizon Telescope (EHT) is a global array of eight radio telescopes working in sync as one larger Earth sized telescope, so to give enough reach and space to photograph this monster black hole. The process of using multiple radio telescopes to build a larger overall picture of something is known as interferometry and interferometers such as The Very Large Array are common on Earth. The EHT project was slightly more ambitious given the distance between each individual point, but nevertheless it did its job. In the future it is hoped that the EHT will be expanded to twelve radio telescopes which will allow for even clearer and more accurate observations of distant intergalactic objects. Using this vast interferometer, a team of 200 scientists and mathematicians pointed the network of telescopes towards M87 and stare at its heart over a period of 10 days in 2017 and took continuous pictures of readings as time passed. Slowly piecing together this mystifying cosmic jigsaw. Due to the size and scale of the project they recorded more scientific data than has ever been recorded by any scientific experiment and so took a lot longer to process than was first anticipated. The data recorded was so great that it was unable to be transmitted over the Internet and so was stored on large hard drives and sent to processing centers in Boston in the USA and Bern in Germany. Obviously eight telescopes no matter how well placed wouldn't be able to compare to an actual earth sized telescope and so the virtual network failed to capture the entirety of the image, but with enough pieces computer algorithms can complete the data and fill in the blanks, sort of like a galactic Sudoku solver. The problem is the sheer amount of extracting data in the radio background noise. MIT PhD student Katie Bouman developed an algorithm that could sift through the data and piece together the image. It took over two years and was released later than expected, but has finally happened. Katie herself has become an overnight celebrity for the leaps and bounds she has made in female achievement in both astronomy and computer science.
And here it is, over two years of processing, 200 scientists, eight radio telescopes, terabytes and terabytes of information over $50 million in funding they have all been pieced together to take a photo of an object over 311 sextillion miles away. Everything has fallen into place, this image is the result of all of those cascading factors, this is one of the greatest astronomical breakthroughs of all time and is one of the most important photographs ever taken.
So, what now? Well if you feel the Event Horizon team was stopping here, you'd be wrong. They will now turn their attention to their initial main target, the supermassive black hole at the center of our own galaxy Sagittarius A*. This sounds easier given its proximity, but unfortunately the accretion disk here is much smaller and less luminous for our local black hole and will require more refined techniques of observation.
In the meantime, though, we can have some fun in speculating on some dark more fantastical mysteries of black holes. For example, everything in the Universe is supposedly describable by information, which defines all the energy and matter within the Universe. Initially Einstein's theory suggested that anything sucked into a black hole may be destroyed and would disappear from the universal together in violation of all of the laws of physics. However, the late Stephen Hawking challenged this and supposes that information never actually reaches a point beyond the black hole singularity and is instead stored behind the event horizon in a sort of flat crushed up hologram. This phenomenon is known as super-translation. While this does mean that the information isn't lost from the Universe, it is still all but destroyed on the journey into the black hole due to its gravitational pull. In a process known somewhat trivially as spaghettification, which becomes so destructive that it separates an object atom by atom and only survives in its simplest most basic and useless form. For all intents and purposes, this circumvents the needs for an inside or a supposed exit from a black hole and answers a problem known as the information paradox.
Now we know that black holes exist as we theorize them, we can start having these conversations regarding what lies beyond or inside them. Alternatively, to Hawking's ideas some believe that a spinning black hole could create a wormhole, an exit point beyond the black hole's event horizon that bends space and time to connect two distant parts of space together, bypassing the distance between them. In fact, some even believe that a black hole could result in a wormhole connecting our Universe to another universe with exit gates into new dimensions known as white holes. Of course, this is all also hypothetical, but again is something we can begin to get excited about the prospect of, now that we know that the gateway into the dark exists. Parallel universes and faster than light travel aside, we've finally achieved confirmation of one of astronomy's two great contemporary mysteries being the existence of black holes the second mystery is the existence and nature of dark matter. With our knowledge of the cosmos strengthened by this picture, we could move towards discovering the nature of dark matter. That is, its existence and its effects on gravity in galaxies and galaxy clusters formations. Ultimately, we still have a lot more to learn and while this image is a giant leap in the right direction, the space beyond the image could hold the answer to more of the mysteries of the Universe. Our knowledge is ever-changing and there will always be more work to be done but with this photograph, we can go forward that little bit more certain about our ideas and models of cosmology and though there is still some way to go this image is still an achievement on the magnificent scale of the black hole itself.