Whatever we know about black holes comes from the equations and theories put forward by physicists like Albert Einstein, Stephen Hawking and others. A long standing goal in astrophysics is to directly observe the immediate surroundings of a black hole and test whether the observations match with the predictions.
The Event Horizon Telescope (EHT) project is an attempt to observe and photograph the immediate environment of a black hole using a number of ground based telescopes. EHT began capturing data in 2006 and plans to release the very first image of the event horizon of the black hole at the center of our galaxy in 2019.
In this article, we present some amazing facts about this project:
1. Telescope of the size of Earth
The Event Horizon Telescope is not a single telescope. Instead, it consists of a network of 15 to 20 radio telescopes located across many different continents on Earth. It works on the technique of very-long-baseline interferometry (VLBI) wherein a large number of radio telescopes separated by hundreds of thousands of kilometers are used in concert to create a virtual telescope of the size of the entire planet!
2. Petabytes of Data!
One reason why the image is taking so long is because of the amount of data that is to be processed. Building the final image would involve processing of about 27 petabytes of data from all different observatories across the planet. (1 petabyte is equal to 1,000,000,000,000,000 bytes.)
3. Capable of spotting a golf ball on the Moon
Because of its huge diameter, EHT has a very high resolving power. The Event Horizon Telescope can resolve features as tiny as 15 micro-arcseconds. That is, it is capable of spotting a tiny golf ball on the surface of the Moon.
4. Testing Einstein’s general relativity
Einstein’s general theory of relativity is the most accepted theory of gravity we have today. It has passed numerous tests with the most recent being the detection of gravitational waves. According to general relativity, a black holes shadow must be circular. Images developed by EHT would help us to test this prediction.
If the shadow cast by the black hole is circular (as predicted by general relativity), Einstein’s theory will pass another major test. But if the shadow is squashed (oblate or prolate), it would imply that we have more physics to understand.
5. Two Black Holes!
EHT will not just photograph Sagittarius A*, the supermassive black hole at the center of our galaxy. The resolution of EHT will allow it to photograph another humongous black hole at the center of M87 galaxy which is about 53 million light years away from us.
This is because the black hole at the center of M87 weighs about 6 billion solar masses i.e. it is roughly 1500 times larger in size than Sagittarius
A*. Although the black hole at the center of M87 is much more distant, it is also much more massive making it appear roughly the same size as Sagittarius A* in Earth’s sky.
6. Sharpest images of a black hole ever produced
Since both the black holes are several thousand light years away, obtaining sharp images is challenging. But EHT will try its best to produce the sharpest images ever obtained. The weather conditions at the telescope sites and the obstruction of light coming from the black hole by the objects in its path might affect the image quality. But given its resolving power, EHT would provide us a lot of insights about the surroundings of a black hole and help us understand these objects in a much better way.
How excited are you for the first direct image of a black hole’s event horizon? Let us know in the comments!
Cover Image Credit: NASA