image: The PLACID instrument.
Credit: University of Bern/PLACID
A game-changing instrument is set to improve the detection and direct imaging of planets outside our Solar System by harnessing the power of liquid crystals. The Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) was installed earlier this year at the 4m-diameter telescope of the newly-built Eastern Anatolian Observatory (DAG) observatory in Eastern Turkey. Now in the integration and validation phase, the first on-sky observations of PLACID are expected in the first quarter of 2026.
PLACID, which has been developed by a team of Swiss researchers from the University of Bern in cooperation with the University of Applied Sciences Western Switzerland of Yverdon (HEIG-VD), will join the small club of direct high-contrast imaging facilities in the northern hemisphere. The technology and status of the instrument, as well as the science it will enable, were presented at the recent EPSC-DPS2025 Joint Meeting in Helsinki.
Most of the nearly 6000 exoplanets discovered to date have been found using indirect methods, which focus on periodic changes of the host star’s apparent properties to infer the existence of a planet. Direct imaging requires an ‘eclipse machine’, known as a coronagraph, to mask the light of a star and reveal any body orbiting it – planets, discs, or brown dwarfs. To date, only a few dozen exoplanets have been directly imaged, as it is highly challenging to take an actual picture of a dim planet next to its very bright host star. Nonetheless, direct imaging is infinitely valuable for scientists as it can provide unique insights into how planets form and their composition, particularly their atmosphere.
“With recent developments in technology and the construction of increasingly large telescopes, the future of exoplanet detection lies in direct imaging. PLACID is one of the stepping stones towards this future,” said Prof Jonas Kühn of the University of Bern in Switzerland, who leads the PLACID project. “It will revolutionise our approach to coronagraphs and bring them into the digital domain.”
Rather than placing a physical plate very precisely in the light path of a telescope, PLACID uses a Spatial Light Modulator (SLM) that relies on the optical properties of liquid crystals to change the optical path or ‘phase’ of light waves for each pixel across a screen. This allows very complex masks to be created at the click of a button.
“We use SLM screens all the time in every-day devices, such as our phones, TVs or computers. In PLACID, the liquid crystals influence how the light passes through each pixel, so we can display any mask we want, giving us an extreme adaptability,” explained Ruben Tandon, a doctoral candidate at the University of Bern and member of the PLACID team.
PLACID’s programming of advanced masks also gives it the exclusive capacity to do direct imaging of so-called circumbinary planets and proto-planetary discs – the cradles for planet formation – orbiting binary or multiple stars. With a traditional coronagraph, this is very challenging, since the unique and variable orbital configuration of each star system makes it almost impossible to set up plates that can block the light from the multiple stars. Thus, while such stars represent about 50% of all stars in our galaxy, no exoplanet orbiting more than one star has been directly imaged to date.
“With PLACID, we can simply adapt the mask in real time to perfectly block the light of any star systems we choose to observe through the night,” said Tandon, who compiled the catalogue of targets for the instrument. “While we will start by targeting the small number of exoplanets that have already been directly imaged to better understand the instrument behaviour, our next step will be to try to directly image exoplanets orbiting binary stars, which will be a first.”
The PLACID instrument, which has been almost a decade in development at the University of Bern, was assembled in the laboratory facilities of the HEIG-VD in Switzerland. After comprehensive laboratory testing to ensure it would meet the expected performances, the instrument was shipped to Turkey in early 2024 and delivered to the DAG telescope for installation in January 2025.
“As with any novel idea, building PLACID involved some risk, but we thankfully benefitted from the support of the National Center of Competence in Research (NCCR) PlanetS and the Division of Space Research and Planetary Science of the University of Bern, who enabled us to do early validation of the technology, before the Türkiye National Observatories (TNO) awarded us the procurement contract. And later, the ERC review panel funded the science exploitation,” said Kühn.
For the instrument performance to be fully harnessed, it also needs to be paired with an Adaptive Optics (AO) system, built by the team of Prof Laurent Jolissaint of HEIG-VD, which will reduce the effects of atmospheric turbulence. The two instruments are in their final stages of installation and will enable PLACID to observe its first targets in the first quarter of 2026.
“We are happy to welcome PLACID. Its capacities, coupled with our 4-meter class telescope, will lead to the first fully-European instrument in the northern hemisphere able to directly image exoplanets,” concluded Derya Öztürk Çetni, the PLACID instrument scientist from TNO.