“Never look down to test the ground before taking your next step; only he who keeps his eye fixed on the far horizon will find the right road.” -Dag Hammarskjold
One of relativity’s oddest predictions is the existence of black holes, objects so dense and massive that nothing, not event light can escape from them. But that lack-of-escaping is limited to a certain volume of space: that within the black hole’s event horizon. Although black holes have been detected and identified, an event horizon has never yet been imaged. That, however, is likely about to change when the Event Horizon Telescope comes online.
The Atacama Large Millimeter submillimeter Array (ALMA) are some of the most powerful radio telescopes on Earth. They are only one small part of the array forming the Event Horizon Telescope. Image credit: ESO/C. Malin.
Given the general relativistic prediction of the size of the supermassive black hole at the center of our galaxy -- 37 microarcseconds -- and the resolution of the EHT that spans the diameter of Earth, its event horizon should be visible. Speculations about black holes date back to 1783, and just a few decades after the first black hole candidate was identified, we’re now prepared to directly image one.
Simulations of how the black hole at the center of the Milky Way may appear to the Event Horizon Telescope, depending on its orientation relative to us. These simulations assume the event horizon exists. Image credit: Imaging an Event Horizon: submm-VLBI of a Super Massive Black Hole, S. Doeleman et al.
Are event horizons real? Get ready, humanity. We’re about to find out!
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Directly imaging the event horizon of Sagittarius A* ! How cool is that?!?!?
Even better is the potential to use the Event Horizon Telescope to test EGR
The size of the event horizon at our galaxy center is expected to be 37 microarcsecs in size, about 2.5 x 2.5 =6 flies on the moon.
As the name suggests, black holes are mostly black, so why do we expect to directly detect the event horizon at all? Isn't it more likely we'll see the accretion disk if there is one out there? If all matter near the black hole has been absorbed by the black hole, would we detect anything at all even if the resolution of the telescope is high enough?
@Anneb #5: Did you read Ethan's article at all? If not, you can find a very brief summary (not intended for use by crackpots, since it assumes that our scientific understanding is correct) at the EHT's Web site: http://www.eventhorizontelescope.org/science/general_relativity.html
Time flies like an arrow
Fruit flies like a banana
On the moon
@Michael, thanks for the link, to me a more clear description, However it is still not clear to me where the photons in the photon ring are coming from. From the accretion disk? From the background stars? From the black hole?
@Anneb #8: The visible "splotch" against which the event horizon shadow is hoped to be seen, is basically the accretion disk of the SMBH.