On 10th April 2019, humans got their first photograph of an actual blackhole. After years of seeing black holes in sci-fi blockbusters (though to be fair, the most accurate depiction on screen has to be the black hole from Interstellar), the real image seems underwhelming to say the least. But what we have achieved is a major milestone in our understanding of our universe.
The remarkable feat was achieved by an international team of scientists working on The Event Horizon Telescope (EHT), a program transformed our planet Earth to become one enormous telescope by combining the power of all radio telescopes around the world.
Einstein’s theory of general relativity predicted the existence of black holes but no one has ever “seen” one. How do you detect an object which emits no light? So far, we have been able to infer by looking at blank spaces in our skies where light seems to bend because they come in contact with a body with a large gravitational field.
The photo above shows a centre of darkness surrounded by a ring of light. The bottom part of the ring seems brighter than the other portions of the ring. My mind is blown for the following reasons:-
- Black holes do not emit light
- Therefore, light seen around blackhole are photons that were captured by the gravitational field
- The border between the dark and the light is the event horizon of the back hole
- This is where the gravitational pull of the blackhole is strong enough to make a photon orbit in place but not strong enough to pull it into the core
- The powerful gravitational pull of a black hole will actually bend light around it, making the light skimming the side of the black hole that’s rotating towards us appear brighter than the light on the side that’s spinning away
What is also remarkable was how close we came to predicting what the blackhole would optically look like:-
ehtim from realistic simulated data similar to the EHT’s observations in 2017. The circle at the lower right represents the EHT’s effective resolutionI sit here in a Starbucks with Cheryl. Saturday mornings is when we drive the girls to music class. I look around and I see people going about their daily lives. There’s an event promoting a(nother) mobile wallet app happening outside. To most people, this major discovery makes no difference in their lives.
Hundred of years from now, all of us- our lives, our names, our concerns, our hopes, our dreams- would have been washed away by the tides of time. It makes me happy that our generation have managed to work together on a discovery that will be lodged firmly in the shores of our fragile and fleeting existence.
See Katie Bouman on TED talking about photographing a black hole years before this remarkable feat of discovery. Her algorithm is the one that is used to render the EHT image of the black hole.