Black holes are the satanic wonders of this Universe. I personally have been interested in them since a very young age, and why shouldn’t I be? They hold so many secrets to the origin of the universe, to what happens when something is sucked into it, or what they actually look like! First predicted by Einstein’s General theory of Relativity, a black hole is what becomes of a star when it collapses under its own gravitational force and thus the contraction causes the gravity to increase so much indeed that nothing, not even light can escape. This is what gives them their name,’Black Holes’. According to Scharzchild’s radius1 formula, if the Earth was to be compressed to a sphere of radius of 1 inch, its gravitational pull would increase so much that even light couldn’t escape and thus it will become a black hole.
Scientists have been fascinated by them since the very beginning, and research is continuously being carried on their behaviour and properties. One of the things that has puzzled us the most is ‘What does a black hole look like exactly?’. Well, we cannot exactly see them, but it has been found that they indeed emit radiation, called Hawking Radiations2 in honour of their predictor Dr. Stephen Hawking. These radiations appear to come from the ‘outline’ of the black hole called the ‘Event Horizon’ which is the point after which not even light can escape the gravity of the black hole. So, it is basically the event horizon that we are trying to picture.
To achieve the above mentioned goal scientists are using the Event Horizon Telescope, which is basically an array of telescopes located all over the world including Antarctica, America, Chile, French Alps, Hawaii and Arizona. This array works on the principle of Very Long Baseline Interferometry3 or VLBI, because of which this network of individual telescopes located all over the Earth behaves as a single Telescope with a diameter similar to that of Earth’s. This gives the telescope an angular accuracy of 50 microarc-seconds which is like being able to see a grapefruit on the surface of the Moon. Observations will be made in the short wavelength region of 1.3mm (frequency of 230Ghz). The telescope is expected to begin functioning between 5-14th April, 2017.
The black hole scientists will be focusing on is the one in the centre of our Milky Way galaxy, called Sagittarius A*, which is about the size of 4 million suns with a diameter of 20 million kilometers, and situated at a distance of 26000 light years from Earth. It is thus like a prick-point in our night sky, thus we can very well imagine how hard it must be to aim at something that small. Unlike the comparably very large black hole in the centre of galaxy Messier 87, Sagittarius A* does not spew any jets of matter or radiation, which adds to the difficulty of measuring it.
“Hopefully, it will look like a crescent – it won’t look like a ring. The rest of the ring will also emit, but what you will brightly pick up is a crescent.” – Ӧzel (University of Arizona)
Till now scientists located black holes by studying the path of the nearby stars under its gravitational field. But now a great revolution in radio astronomy can be expected with the inauguration of the EHT. The short wavelength of the telescope will help view right through the clouds of gases and dust, and increase clarity. What scientists are expecting the first picture of the black hole to be like is ‘ A bright ring around a dark blob’, the bright ring is the visible event horizon(because of the radiations given off by particles just before they are torn apart), and the dark blob is the black hole’s darkness. To be precise, Relativity predicts a crescent of light instead of a full spherical ring, this is because of doppler effect4. This is because black holes have a spin, or angular velocity, depending on their size, so the radiation from the part moving towards us will reach faster than the one moving away and thus through Doppler’s effect and Relativity predictions, we will see a crescent ring. Thus, the experiment will put the theory of Relativity to tests like never before. If the picture is any different from what the theory predicted, which is not very much probable (Because Einstein, Duh!), this would change Physics as we know it.
Results from the study can be expected by the end of the year or early 2018, and I bet, this will be just as if not more thrilling as the Pluto flyby. So hold on, and wait to see a black hole for the first time in forever,because Black Holes ain’t Black after all.
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“One thing that could excite the public almost as much as a Pluto flyby would be a picture of a black hole, up close and personal,”- Ӧzel at the 227th meeting of the American Astronomical Society
-The Cosmogasmic Person.
Some Definitions To Help The Curious Readers :-
- Scharzchild’s radius is the radius of the sphere to which if any body is compressed, its gravity becomes so high that even light cannot escape. It depends on the initial size of the body.
- Hawking showed that quantum effects allow black holes to emit exact black body radiation. The electromagnetic radiation is produced as if emitted by a black body with a temperature inversely proportional to the mass of the black hole.
- VLBI uses data from the individual telescopes and the time interval between arrival of signal at one station to another, and then combines this data to form one signal image, comparable to one formed by a single telescope with the diameter equal to the maximum distance between two telescopes.
- Doppler’s effect is the change in original frequency when received by an observer/receiver because of the velocity of the body that is emitting them. The effect is proportional to the magnitude of velocity, and frequency decreases when the body is moving towards you and increases when moving away.