Today’s post will be explaining the workings of the Event Horizon Telescope and the recent efforts to capture for the first time an image of the black hole at the center of our galaxy.
The Event Horizon Telescope is a truly global endeavour as it consists of eight radio observatories in six different locations around the world: Spain, Arizona, Hawaii, Mexico, Chile and Antarctica – creating a telescope array as wide as Planet Earth. The set-up is that each telescope points at the black hole at the center of our galaxy, known as Sagittarius A*, and measures the radio waves coming from its direction, collecting more detailed data than we have ever had before. The telescope should achieve a resolution of 50 microarcseconds which is equivalent to being able to see a melon on the moon! Equipped with this resolving power we should be able to image the event horizon of Sagittarius A*, which although being a whopping 20 million km wide is to us but a pinprick in the night sky 26,000 light years away.
The plan was that the telescopes were all to be turned on for 5 nights between April 5th and April 14th, the exact timings being chosen dependent on the best weather conditions. It can now be confirmed that last night the astronomers operating the sites finished their spell of observations and the data is now in the bank so to speak. Each nights the telescopes generated a total of 2 petabytes of data, which according to a calculation by New Scientist, is enough to store the full genomes of 2 billion people! So, as you can image all this data is going to take a decent old time to process before we can see any results.
Now I may hear you say “Hold on, take an image of a black hole?! But I thought black holes were unable to be seen due to the very nature of things not being able to escape that go beyond its horizon, not even light!” Well right you are, but what astronomers hope to see is the matter that hurtles around the horizon edge, being bent by the intense gravity as it is slowly sucked towards the center of darkness. Even light is bent by the immense gravitational pull so the perimeter of the black hole should glow intensely as the photons (that are just far away enough to avoid being sucked in) spin round and round the horizon. Therefore if our predictions are correct we should see this bright circle of light warped around the shadow within.
Event horizons have been somewhat of a mythology of science. In fact the existence of black holes was once debated whether to be science-fiction or science-fact, as they were purely a theoretical prediction of Einstein’s general relativity. However in this case seeing really would be believing if the images came out just as the theory predicts them to. Taking things to the next level, if we can get accurate images to actually measure the size of the dark shadow we can test general relativity further as the theory can predict what size the black hole should be dependent on its mass.
However perhaps we’re going to see something different entirely to our predictions. Now this may not be the worst outcome in the world.. in fact it may lead us further along in our attempts to resolve the conflicts between general relativity and quantum mechanics. As it stands the two theories do not fit together and our predictions for the nature of a black hole go no way to resolving this. Often the most extreme environments in nature are the ones which give us the best insights into the rules by which nature plays and the black hole is the most extreme gravitational environment out there. If our observations prove us wrong perhaps it’ll be a push in another more fruitful direction for physics.
Then again, taking history’s track record one should know better than to bet against Einstein. The Event Horizon Telescope should prove that event horizons really exist (else the project might need a re-brand). Now it’s just a question of time and some hard-core data-analysis to get the findings up. The information from all the telescopes – equivalent to the storage capacity of ten thousand laptops – must be physically sent to the telescope’s processing enters in MIT and the Max Planck Institute for Radio Astronomy and to make matters worse the drives from the South Pole site can’t be flown out until the end of winter season there, in November! The technique of combining radio wave signals is known as ‘very long baseline interferometry’ and although it is a common technique amongst astronomers the sheer amount of data in this case is unprecedented. It’s not certain that this initial run by the Event Horizon Telescope will be successful in generating a clear image but the team has plans to conduct repeat observations, extend the network to more sites and eventually into space to work towards an even sharper signal.
So for now all we can do is sit back, relax and let the astronomers do their biz as we await to see for the first time if the mask can pulled off the mysterious character that is the black hole.