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Interferometry II

February 9, 2016

HL Tauri is like a newborn version of our own solar system, with a Sun-like star surrounded by a disk of gas and dust.

HL TauriALMA view of HL TauriA remarkable image of the system reveals bright rings and dark gaps within the disk — sculpted by planets. The planets grow by sweeping up the gas and dust around them, clearing out gaps. And the planets’ gravity causes the remaining gas and dust to concentrate in the bright rings.

This image of HL Tauri was made with a technique known as interferometry. It combines the light from two or more telescopes to create images that are as sharp as those made by a single telescope that’s as big as the distance between the individual telescopes.

ALMA telescopeMany of the ALMA dishes shine beneath the Magellanic Clouds, two companion galaxies to the Milky Way [ESO/Christoph Malin]The picture of HL Tauri, for example, was taken by ALMA, a radio telescope in Chile. It consists of dozens of individual radio dishes that can be spread up to about 10 miles apart. That provides images that are as sharp as the view from a single radio dish 10 miles wide, but at a fraction of the cost.

Making an interferometer work isn’t easy, though. For example, the observations from the individual telescopes have to be precisely synchronized. If the timing is off by a millionth of a second, the observations are ruined. In most radio interferometers, the observations from each dish are recorded and later combined with a powerful computer.

A few interferometers look at visible light, which is even trickier than radio waves. We’ll have more about that tomorrow.

Script by Damond Benningfield


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