Free Astronomy Magazine March-April 2026

29 MARCH-APRIL 2026 ASTRO PUBLISHING where exactly it was coming from. “Since the ‘90s, it has not been pos- sible to explain excess infrared emis- sions that come from hot dust at the cores of active galaxies, meaning the models only take into account either the torus or the outflows, but can- not explain that excess,” said Lopez- Rodriguez. Such models found that most of the emission (and, there- fore, mass) close to the center came from outflows. To test this theory, then, astronomers needed two things: the ability to filter the star- light that previously prevented a deeper analysis, and the ability to distinguish the infrared emissions of the torus from those of the out- flows. Webb, sensitive and techno- logically sophisticated enough to meet both challenges, was necessary to advance our understanding. To look into the center of Circinus, Webb needed the Aperture Masking Interferometer tool on its NIRISS (Near-Infrared Imager and Slitless Spectrograph) instrument. On Earth, interferometers usually take the form of telescope arrays: mirrors or antennae that work together as if they were a single telescope. An in- terferometer does this by gathering and combining the light from whichever source it is pointed to- ward, causing the electromagnetic waves that make up light to “inter- fere” with each other (hence, “inter- fere-ometer”) and creating interfer- ence patterns. These patterns can be analyzed by astronomers to recon- struct the size, shape, and features of distant objects with much greater detail than non-interferometric tech- niques. The Aperture Masking Interferome- ter allows Webb to become an array of smaller telescopes working to- gether as an interferometer, creat- ing these interference patterns by itself. It does this by utilizing a spe- cial aperture made of seven small, hexagonal holes, which, like in pho- T his zoom-in video shows the location of the Circinus galaxy on the sky. It be- gins with a ground-based photo of the constellation Circinus by the late as- trophotographer Akira Fujii. The video closes in on the Circinus galaxy, using views from the Digitized Sky Survey and the Dark Energy Survey Camera aboard the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observa- tory. The video lands on the visible light image of the galaxy from NASA’s Hub- ble Space Telescope, then zooms in even more to the image of the galaxy’s core from NASA’s James Webb Space Telescope’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) in near-infrared light. [NASA, ESA, CSA, Alyssa Pagan (STScI); Acknowledgment: CTIO, NSF’s NOIRLab, DSS, Akira Fujii] https://science.nasa.gov/asset/webb/circinus-galaxy-zoom/ tography, controls the amount and direction of light that enters the telescope’s detectors. “These holes in the mask are transformed into small collectors of light that guide the light toward the detector of the camera and create an interference pattern,” said Joel Sanchez-Bermu- dez, co-author based at the National University of Mexico. With new data in hand, the research team was able to construct an image from the cen- tral region’s interference patterns. To do so, they referenced data from previous observations to ensure their data from Webb was free of any artifacts. This resulted in the first extragalactic observation from an infrared interferometer in space. “By using an advanced imaging mode of the camera, we can effec- tively double its resolution over a smaller area of the sky,” Sanchez- Bermudez said. “This allows us to see images twice as sharp. Instead of Webb’s 6.5-meter diameter, it’s like we are observing this region with a 13-meter space telescope.” The data showed that contrary to the models predicting that the infrared excess comes from the outflows, around 87% of the infrared emissions from hot dust in Circinus come from the areas closest to the black hole, while less than 1% of emissions come from hot dusty outflows. The re- maining 12% comes from distances farther away that could not previ- ously be told apart. “It is the first time a high-contrast mode of Webb has been used to look at an extra- galactic source,” said Julien Girard, paper co-author and senior research scientist at the Space Telescope Sci- ence Institute. “We hope our work inspires other astronomers to use the Aperture Masking Interferome- ter mode to study faint, but rela- tively small, dusty structures in the vicinity of any bright object.” !