Aperture Masking Interferometry (AMI) Simulation

This animation shows a theoretical scenario to explain how an observational technique known as aperture masking interferometry (AMI) is conducted with NASA’s James Webb Space Telescope’s NIRISS (Near Infrared Imager and Slitless Spectrometer) instrument. This method enables high-angular resolution imaging, which is useful for observing celestial objects that appear small in the sky.

At left, a schematic diagram of NIRISS’ relevant mask that enables AMI is shown. The mask has seven hexagonal pinholes, which are where light can enter and reach the detector. Six lines emanate from each of the seven pinholes to indicate that these pinholes are paired up and their placement is intentional.

Using a star as the example target, the video then shows the schematic diagram at left and the simulated image as it would appear according to the NIRISS instrument at right. Although the seven pinholes are always open when using this mask for real observations, the animation sequentially opens the holes to show how the pattern of light — also called a fringe pattern — changes with each addition.

With one pinhole open, the light looks like a fuzzy, unfocused circle of light. With each added pinhole, the fringe pattern changes.

With this method, different celestial objects produce different fringe patterns of light on Webb’s detector. Astronomers have used this approach for a variety of objects, including stars and planetary moons, to acquire additional information that cannot be gathered from standard imaging alone.

Read about the science made possible with AMI.