Nulling interferometry is a technique which cancels the overwhelming glare from a star by interference of light, thus allowing for the detection of nearby planets or dust discs which would otherwise be obscured by the much brighter star.

Without nulling

The above image shows the two lightwaves are in perfect alignment, which amplifies the light coming from the distant star.

Star partially nulled

In the above image, the two lightwaves are beginning to cancel, or null, each other out. As a result, the bright light from the distant star begins to fade, revealing the dimmer dust cloud. The nuller is designed to tune out light at stellar wavelenghts, while allowing the longer wavelenghts of the dust cloud to remain visible.

Star fully nulled

The final image, above, shows the starlight almost completely nulled and the disc-like cloud is now clearly visible.

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