Monday, February 20, 2017
Scientists Are About to Switch on a Telescope That Could Photograph a Black Hole's Event Horizon - UNIVERSE
Called the Event Horizon Telescope, the new device is made up of a network of radio receivers located across the planet, including at the South Pole, in the US, Chile, and the French alps.
The network will be switched on between 5 and 14 April this year, and the results will put Einstein's theory of general relativity through its paces like never before.
The Event Horizon Telescope works using a technique known as very-long-baseline interferometry (VLBI), which means the network of receivers will focus in on radio waves emitted by a particular object in space at one time.
For the black hole, they'll be focusing on radio waves with a wavelength of 1.3 mm (230 GHz), which gives them the best chance of piercing through any clouds of gas and dust blocking the black hole.
And because there are so many of these antennae all tuned in on a single spot, the resolution of the telescope should be 50 microarcseconds. To put that into perspective, it's the equivalent of being able to see a grapefruit on the surface of the Moon
That's important, because the first target will be the huge black hole at the centre of our galaxy, called Sagittarius A*, which is actually only the size of a pinprick in our night sky.
We've never directly observed Sagittarius A*, but researchers know it exists because of the way it influences the orbit of nearby stars.
Based on the behavior of these stars, researchers predict that the black hole is likely about 4 million times more massive than our Sun, but with an event horizon diameter of just 20 million km (12.4 million miles) or so across.
At a distance of around 26,000 light-years away from Earth, that makes it a pretty small target.
But the Event Horizon Telescope will aim to observe the immediate environment around the black hole, and it should be able to get enough resolution to see the black hole itself.