VLBI, or Very Long Baseline Interferometry, is a technique used in radio astronomy to study celestial bodies. The word is spelled with a voicing contrast between the initial letters ‘v’ and ‘l’. The ‘v’ is pronounced as the voiced labiodental fricative /v/, while the ‘l’ is pronounced as the voiceless alveolar lateral approximant /l/. The following letters ‘b’ and ‘i’ have their usual pronunciations, with ‘b’ as the voiced bilabial stop /b/ and ‘i’ as the high front unrounded vowel /i/.
Very Long Baseline Interferometry (VLBI) is a technique used in radio astronomy and geodesy to observe and precisely measure objects in space or monitor the Earth's rotation and tectonic movements. VLBI involves combining the signals received from multiple radio telescopes separated by great distances to create an interferometer with an extremely long baseline. This technique allows for unprecedented high-resolution imaging and precise positional measurements.
VLBI works by synchronizing the precise measurement of arrival times of radio signals from celestial objects, typically distant quasars or pulsars, at each telescope. These signals are then combined and correlated to form an interference pattern. By correlating the signals received at different telescopes, VLBI can effectively simulate a large single telescope, allowing astronomers to achieve much higher resolution than any individual telescope could provide alone.
The resulting high-resolution images produced by VLBI provide scientists with detailed information about celestial objects such as quasars, active galactic nuclei, pulsars, and black holes. In geodesy, VLBI is utilized to monitor the Earth's rotation, determine precise positions of fixed points, and study plate tectonics and crustal movements with millimeter-level accuracy.
VLBI has significantly contributed to astrophysical research, geodetic studies, and global navigation systems. It revolutionized our understanding of the universe by revealing intricate details of celestial objects and their dynamics, as well as enhanced our ability to precisely measure and monitor Earth's movements.