Very Long Baseline Array

The Very Long Baseline Array (VLBA) is a network of ten radio telescopes across the United States that observes together using very long baseline interferometry.

Very long baseline interferometry: A radio astronomy technique that combines signals recorded by widely separated telescopes to produce exceptionally high angular resolution. The VLBA is a dedicated observatory built to use this technique.
Active galactic nucleus: A galaxy’s exceptionally bright central region, powered by matter accreting onto a supermassive black hole. VLBA images resolve compact cores and jets in these energetic galaxies.
National Radio Astronomy Observatory: A United States research institution that operates major radio astronomy facilities. The observatory operates the VLBA and coordinates its scientific use.
Very Large Array: A radio interferometer in New Mexico made up of twenty-seven movable antennas. Unlike the VLBA’s continent-spanning fixed stations, the VLA uses a compact, reconfigurable array.
Radio interferometry: A method of combining radio signals from multiple antennas to measure astronomical sources with improved angular resolution. The VLBA applies this broader method across continent-scale distances.
Astrometry: The measurement of the positions and motions of celestial objects. VLBA observations can determine precise radio-source positions and motions.
Very Long Baseline Array construction: The design and building of the VLBA’s ten-station radio telescope network. Its construction established a dedicated array rather than relying only on ad hoc telescope partnerships.
Event Horizon Telescope: A global network of radio observatories that performs very long baseline interferometry at millimeter wavelengths. The EHT targets horizon-scale imaging with a global network, unlike the VLBA’s dedicated centimeter-wave array.
VLBI correlator: A computing system that aligns and correlates recorded signals from separate radio telescopes. Correlation turns the VLBA’s independent recordings into interferometric measurements.
Proper motion: The apparent angular change in an object’s position across the sky over time. Repeated VLBA measurements track motions of stars and radio sources.

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