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What is an astronomical interferometer?

ESO’s Very Large Telescope Interferometer

Image: VLTI Very Large Telescope Interferometer (4 combined fixed telescopes and 4 small mobile telescopes).
Credit ESO.

What is an astronomical interferometer?

An astronomical interferometer consists of several separate telescopes which combine their signals, in order to offer a resolution equivalent to that of a telescope of diameter equal to the greatest distance which separates the individual telescopes. The basic principle of an astronomical interferometer is to combine signals from two or more telescopes located at different locations. Telescopes are usually located on bases separated by several kilometers to maximize the resolution of the image of distant objects (stars, quasars, black holes or galaxies).

The signal from each telescope is collected and guided to a central point where they are combined. The resulting interference creates a high-resolution image of the light source, which is much more detailed than could be obtained with a single telescope.

Astronomical interferometers can also be used to measure the distance between stars, which is important for understanding the structure of our galaxy.

The largest existing astronomical interferometers:

• The Very Large Telescope Interferometer (VLTI) at the European Southern Observatory (ESO) in Chile, which combines signals from four 8.2-meter telescopes.

• The Keck Interferometer, which combines the signals from the two 10-meter Keck telescopes located in Hawaii.

• The LBT Interferometer, which combines signals from the two 8.4-meter telescopes at the Mount Graham Binational Observatory in Arizona

• The CHARA Array, which combines signals from six 1-meter telescopes located in Georgia.

• The Magdalena Ridge Observatory Interferometer (MROI), an interferometer under construction in New Mexico that will combine signals from ten 1.4 meter telescopes.

These interferometers provide high-resolution images that can be used to study a variety of astronomical phenomena, including star evolution, planet formation, and the structure of our galaxy.

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