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Black Hole Outline

June 27, 2016

The constellation that marks the center of the Milky Way galaxy scoots low across the south on summer nights. Its brightest stars form the outline of a teapot, with the glowing band of the Milky Way rising from the spout like steam. The galaxy’s heart is inside the steam.

A supermassive black hole sits at the center of this region. It’s known as Sagittarius A-star, after the constellation. It weighs as much as four million Suns.

Astronomers determined that mass by measuring the orbits of nearby stars. As the stars get closer to the black hole they speed up. The speed indicates the presence of a small, heavy concentration of matter that tugs at the orbiting stars.

Yet no one has seen the black hole itself. Its event horizon — the point of no return for matter that falls into the black hole — is about 14 million miles in diameter. That’s a big target. But from a distance of about 27,000 light-years, that’s too small to measure with any existing telescope.

Yet there’s an effort underway to see the black hole nonetheless. Astronomers are linking radio dishes around the world in a project known as the Event Horizon Telescope. Combining several widely spaced telescopes produces images as sharp as those made by a single telescope as big as Earth.

The goal is to see the outline of the black hole. The black hole’s gravity should distort the view of the stars and gas behind it, producing a glowing ring — outlining a black hole.

Script by Damond Benningfield

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