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Interferometry III

February 10, 2016

Combining the views from two or more optical telescopes provides a sharper image of the heavens. But it requires extreme precision to make it work.

The technique is known as interferometry. Light waves from the individual telescopes “interfere” with each other when they’re combined. The way they interfere allows astronomers to produce images of astronomical objects.

Interferometry’s advantage is that the combined telescopes see the universe as clearly as a much bigger single telescope. And the farther apart they are, the sharper their vision.

For an interferometer to work, the light from all the telescopes must come together at precisely the same time. That’s a complicated task. A star’s light reaches each telescope at a slightly different time. And the telescopes will be placed at different distances from the instruments that combine and analyze their light. Those differences add up to a few billionths of a second — but that’s enough to ruin the view.

One way to compensate is to send the light from each telescope through a series of vacuum tubes and mirrors. The light from a closer telescope follows a longer path, making sure it reaches the instrument at the same time as light from a more-distant telescope.

As more telescopes are added, the view improves — but making it work gets tougher. We’ll talk about an array that’s designed for 10 telescopes — the Magdalena Ridge Observatory Interferometer in New Mexico — tomorrow.

Script by Damond Benningfield


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