Interferometer array sees first light, and into the future

The Magdalena Ridge Observatory Interferometer (MROI) achieves “First Fringes”, hitting a crucial benchmark for proof of concept.

The Magdalena Ridge Observatory Interferometer is an ambitious astronomy installation developed by New Mexico Tech (NMT) in partnership with the University of Cambridge, UK, and the U.S. Air Force Research Laboratory. On Saturday 12 July 2025, the interferometer successfully achieved “first fringes.” This long-awaited proof-of-concept marks a critical step in a project more than two decades in the making and signals the dawn of a new era in high-resolution imaging of the cosmos.

“This is a fantastic achievement for the whole project team and a long-awaited validation of a design that was first put on paper years ago.”

Prof Chris Haniff

The milestone measurement was recorded shortly before 3 a.m. local time (Mountain Daylight Time), when MROI combined the light from two of its telescopes for the first time.

Dr Michelle Creech-Eakman, professor of physics and MROI Project Scientist at NMT, said, “We targeted Epsilon Cygni. For proof of concept, the team needed to look at a very bright, nearby, familiar celestial body. This bright star in the Swan constellation was perfect. The resulting interference pattern, known as ‘fringes,’ confirms that the instrument’s complex systems – from its telescopes and vacuum-sealed delay lines to its cryogenically cooled detectors – can work in precise, real-time coordination.”

The MROI is designed to be exceptionally sensitive, requiring its light-guiding delay lines to be held in vacuum tubes and aligned with precision finer than the width of a human hair.

“Every component, down to the concrete piers and the half-dozen mirrors in the light path, had to perform perfectly. Achieving first fringes is the equivalent of successfully flying the glider you’ve built from a kit; it proves the fundamental design is sound. This success is a testament to the incredible dedication of our international team over the last 20 years.”

“This is a fantastic achievement for the whole project team and a long-awaited validation of a design that was first put on paper years ago,” said University of Cambridge Professors Chris Haniff and David Buscher. Along colleagues at the Cavendish Laboratory in Cambridge, Haniff and Buscher have led much of the design of the MROI. The earliest attempts to use arrays of telescopes to create images of stars in visible and infrared light were made by their small team at the Cavendish Laboratory in Cambridge, back in the late 1980s and early 1990s.

Much of the equipment at MROI has been improved, thanks to lessons learned in those early Cambridge experiments, especially when it comes to the vacuum delay lines, those tubes that protect the light paths, and the “Fast Tip-Tilt” system that helps the telescopes handle changing weather.

“Getting these results so soon after we set up the first instrument augurs well for our next steps, which are to push the robustness and sensitivity of the telescopes even further, so we can study much dimmer stars and objects in space with a level of detail that has never been before possible for astrophysics here on Earth,” said Haniff.

This initial success, achieved with an 8-meter separation between telescopes, sets the stage for the facility’s future. When complete, the MROI will feature 10 telescopes with separations of up to 340 meters. It will produce images with unprecedented detail and is designed to observe astronomical targets more than 100 times fainter than what is possible with similar instruments today, as Dr. Creech Eakman said, “providing a resolution equivalent to measuring the height of a small child standing on the Moon.”

Since obtaining first fringes, the project now captures fringes on multiple targets during a single observing night on objects that range down to magnitude 8.9 at H-band, which is roughly 3000 times fainter than the first observations. All indications are the instrument will be able to do as its design intends and capture fringes on much fainter (a factor of 70) targets.

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Adapted from an article by New Mexico Tech.

To go further:

• Big Think long-read article: Astronomy’s secret weapon in the resolution wars: interferometry by Ethan Siegel
• Big Think podcast: Starts With A Bang podcast #110 – Optical Interferometry with Prof Haniff and Dr Michelle Creech-Eakman