A black hole’s gravitational field is so strong light cannot escape. So how did they take one’s picture?
Key Vocabulary: General relativity, medium, spacetime, black hole, event horizon, gravity, radio telescope, galaxy
Next Generation Science Standards:
- HS-ESS1-2. Construct an explanation of the Big Bang theory based on astronomical evidence of light spectra, motion of distant galaxies, and composition of matter in the universe.
- HS-ESS1-3. Communicate scientific ideas about the way stars, over their life cycle, produce elements.
Yesterday, researchers shared with the world the first picture of a black hole ever taken. The Event Horizon Telescope, an array of radio telescopes across the planet, released an image of M87, a black hole at the center of a galaxy 55 million lightyears away.
Albert Einstein first predicted the existence of black holes when he proposed his theory of General Relativity in 1915. General Relativity explains the force of gravity caused by curves in the spacetime continuum. Einstein hypothesized that there were some objects so massive and their gravitational pull so strong, that nothing, not even light can escape. M87 has a mass of roughly 6.5 billion times that of our sun. For a long time, astrophysicists weren’t sure that such objects could even be observed, even if their existence was likely. But after years of international collaboration, the world can finally gaze upon one of the strangest objects in the universe.
So how did researchers pull this off? By essentially turning the entire planet into one giant radio telescope. By using linking a network of eight pre-existing telescopes from Hawaii to Antarctica, the team significantly increased what they could observe. The feat is extremely impressive, the equivalent of taking an image of a grapefruit on the moon but with a radio telescope. Wandering Planet, a PhD student from Chile, put together the illustration below, which beautifully explains black holes and how they can be observed.
- Katie Bouman was on the team of astronomers for the Event Horizon Telescope. Her algorithm was used to put together the image of M87. She explains her work in a TED talk from November 2016.
- This picture form XKCD shows the size of M87 compared to the Sun and the Solar System.