Black Hole watching

Credit: Hotaka Shiokawa/CFA/HARVARD

They have built an Earth-sized “virtual telescope” by linking a large array of radio receivers – from the South Pole, to Hawaii, to the Americas and Europe.
There is optimism that observations to be conducted during 5-14 April could finally deliver the long-sought prize.
In the sights of the so-called “Event Horizon Telescope” will be the monster black hole at the centre of our galaxy.
Although never seen directly, this object, catalogued as Sagittarius A*, has been determined to exist from the way it influences the orbits of nearby stars.
These race around a point in space at many thousands of km per second, suggesting the hole likely has a mass of about four million times that of the Sun.
But as colossal as that sounds, the “edge” of the black hole – the horizon inside which an immense gravity field traps all light – may be no more than 20 million km or so across.
And at a distance of 26,000 light-years from Earth, this makes Sagittarius A* a tiny pinprick on the sky.
The Event Horizon Telescope (EHT) team is nonetheless bullish. … (BBC)

Credit: Hotaka Shiokawa/CFA/HARVARD

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