Astronomy has long known a technique: if you combine the light from several telescopes, you can achieve a resolution unavailable to a single instrument. This is how the CHARA array in California works - an installation of six telescopes acting as one giant instrument. But the light from each telescope must be combined with jeweler's precision, and for this, bulky systems of mirrors and lenses are usually built.
Researchers from Heriot-Watt University (UK) have proposed performing this work with the help of a tiny photonic chip - a glass plate about two centimeters in size. Inside it, thin channels are written with ultrashort laser pulses, along which light propagates in the same way as electrons in a microchip. The chip was successfully used for the first time for observations of the real sky on the CHARA array. The results are published in the journal Monthly Notices of the Royal Astronomical Society.
The chip became the heart of the CHARIOT instrument, created as a test platform for new photonic technologies. During the observation campaigns of 2024 and 2025, CHARIOT combined light from the CHARA telescopes and recorded signals from a number of stars. The instrument also detected signals from stars fainter than those recorded by the system it replaced. This shows that the technology provides the precision needed for advanced astronomical research.
The project brought together specialists from the UK, Germany (the Universities of Cologne and Potsdam) and the USA (the CHARA array of Georgia State University). The chip was developed at the Institute of Photonics and Quantum Sciences of Heriot-Watt University under the leadership of Professor Robert Thomson and Dr. Aurelien Benoit. They also played a key role in the observations that confirmed the device's operability.
"Traditionally, combining light from several telescopes requires bulky instruments with a complex system of mirrors and lenses. We have shown that a significant part of this work can be performed by a glass plate only a couple of centimeters in size," a press release quotes Thomson as saying. According to him, the path from fundamental research and laboratory demonstrations to work at one of the world's leading observatories took more than 15 years.
One of the main advantages of CHARIOT is flexibility. Different photonic chips can be removed and replaced within a few hours, which allows improved designs to be tested quickly. The work belongs to the field of astrophotonics, which uses advanced light technologies to solve complex problems in astronomy.
The authors emphasize: for now this is the first step. In the future, such chips could help study the formation and evolution of planetary systems, as well as directly detect and characterize planets around other stars. However, this is a prospect, not an already solved problem. Only the very possibility of combining telescope light with the required precision using a compact glass chip has been demonstrated - and this is an important step toward a new generation of astronomical instruments.