Image description: VLTI (Very Large Telescope Interferometer), combining 4 fixed telescopes and 4 mobile telescopes. Image source: ESO
An astronomical interferometer combines signals from multiple separate telescopes to achieve a resolution equivalent to that of a single telescope with a diameter equal to the maximum distance between the telescopes. The telescopes are often spaced several kilometers apart to maximize the resolution of images of very distant objects such as stars, quasars, black holes, or galaxies.
The signals are collected and directed to a central point where interference produces a high-resolution image, much more detailed than with a single telescope.
Interferometers also allow precise measurement of the distance between stars, which is crucial for understanding the structure of our galaxy.
Here are the most powerful interferometers, ranked by capacity and location:
| Interferometer | Agency / Observatory | Number of Telescopes | Telescope Diameter | Location | Comments |
|---|---|---|---|---|---|
| VLTI | ESO, Chile | 4 fixed + 4 mobile | 8.2 m | Paranal Observatory | Combines several telescopes to achieve exceptional resolution |
| Keck Interferometer | Keck Observatory, Hawaii | 2 | 10 m | Mauna Kea | Enables precise observations of stars and exoplanets |
| LBT Interferometer | Mount Graham Observatory, Arizona | 2 | 8.4 m | Arizona, USA | Binational Italian-American observatory |
| CHARA Array | Georgia State University, USA | 6 | 1 m | Mount Wilson, Georgia | Excellent for measuring stellar diameters and interstellar distances |
| MROI | Magdalena Ridge Observatory, New Mexico | 10 (under construction) | 1.4 m | New Mexico, USA | Will allow high-resolution imaging of multiple stars simultaneously |
These interferometers allow the study of: stellar evolution, planet formation, binary interactions, galactic structure, and the detection of circumstellar disks. They are now an essential tool for astronomers seeking to push beyond the limits of single telescopes.
GRAIL Twin Probes: Mapping the Moon's Hidden Interior 
Earth Under Surveillance: Observation Satellites 
March 2010: The Ring of Fire Captured by the SDO Observatory 
Positions of Space Probes in 2025 
Giants of Observation: The Largest Ground-Based Telescopes 
Low Earth Orbits and their uses 
Pioneer, first message to extraterrestrials ! 
How to see infrared images from JWST? 
Sputnik 1 and 2: The Dawn of the Space Age 
ENVISAT: Ten Years of Uninterrupted Observation of Earth's Ecosystems 
Lagrange Points: Gravitational Gateways of the Solar System 
Mars Reconnaissance Orbiter: The Lynx Eye Revealing Martian Secrets 
Kepler: 4,000 Worlds and More, A New Map of the Sky 
Why Measure Space at the Nanometer Level? 
High-risk landing for Curiosity in 2012 
Cheops Space Telescope: A New Vision on Exoplanets 
The world of Planck 
Rosetta Space Probe: Comet Churyumov-Gerasimenko 
The Hubble Space Telescope: Three Decades of Revelations 
Première photo du télescope Hubble 
Satellites that measure underwater relief 
MESSENGER: The First Probe to Visit the Mysterious Planet 
How GPS Locates Your Position at Any Time? 
The ISS and Beyond? Towards the End of a Space Chapter 
Space Telescopes: Humanity's Eye Beyond the Atmosphere 
Space Probes: Interplanetary Travelers and Beyond
The GAIA satellite maps the Milky Way 
How to calculate the synchronous orbit? 
E-ELT: The World's Largest Optical Telescope 
Mercury probes 
Space Debris: The Nightmare of Modern Satellites 
Aquarius: A Mission to Map Ocean Salinity 
JWST: An Unprecedented Look at the First Lights of the Universe 
METEOSAT: A Key Satellite for Climate Monitoring 
Curiosity, the first shovel, sample of Martian soil 
From Mariner to Perseverance: Successes and Failures of Mars Probes 
Where is the geostationary orbit? 
MOM, the technological demonstration 
Venus probes 
What Is an Astronomical Interferometer?
The Philae Robot and the Rosetta Comet 
Mauna Kea Under the Stars: The CFHT Telescope in Pursuit of the Universe's Mysteries