A black hole emits no light, so the thing itself cannot appear in any image. General relativity predicts something adjacent: immersed in a bright region such as a disc of glowing gas, a black hole should carve out a dark region. Nobody had ever seen it.
Its shadow, and a ring of light bent around it. The Telescope revealed a ring-like structure with a dark central region at the heart of , 55 million light-years away. The black hole there carries a mass 6.5 billion times that of the Sun, and the shadow comes from light bent and captured by the event horizon.
The Event Horizon Telescope is a of eight ground-based radio telescopes, forged through international collaboration and designed to capture images of a black hole. In April 2019 its researchers unveiled the first direct visual evidence of a supermassive black hole and its shadow.
The prediction being tested is specific. Immersed in a bright region, such as a disc of glowing gas, a black hole should create a dark region similar to a shadow. The gravitational bending and capture of light by the event horizon causes it.
The target was chosen for size on the sky. The image reveals the black hole at the center of Messier 87, one of the largest galaxies in the nearby Virgo cluster. It resides 55 million light-years from Earth, with a mass 6.5 billion times that of the Sun.
What persuaded the team was repetition. Multiple and imaging methods revealed a ring-like structure with a dark central region, and it persisted over multiple independent EHT observations. Many features of the image match theoretical models of warped space, superheated matter and strong magnetic fields.
wat. The dark circle is the only part that is actually the black hole.
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It is a direct visual test of general relativity at the one place the theory is hardest to check.
How do we know?
Eight ground-based radio telescopes were linked into an Earth-sized virtual instrument, and multiple independent calibration and imaging methods produced the same structure across separate observations.
What is still unknown
An image of the shadow and the light around it, not of the object, which by definition cannot be seen.
Learn something?
Where to next
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