Radio interferometry is an advanced technique, developed by professional radio astronomers, that allows to use many smaller antennas instead of a too large one. In fact, when we think of a radio telescope, we imagine an instrument of enormous dimensions, equipped with a very large parabolic antenna that collects radio waves coming from space. By using many compact radio telescopes, radio interferometry improves results in radio astronomy research and allows the use of more affordable radio telescopes. For example, by using this technique the Event Horizon Telescope (an international collaboration of multiple radio telescopes from all over the world) recorded, in April 2019, the first radio map of a black hole inside the M87 galaxy, with an incredible resolution of 25 microarcseconds!

Radio astronomy is a fascinating science and it studies the Universe by detecting radio emission from many objects like the Sun, the Milky way, planets, galaxies and nebulas. In this presentation Filippo Bradaschia, PrimaLuceLab president and co-founder, gives an overview on radio astronomy history and basic physics. Then he introduces the most important radio sources in the Universe and the SPIDER affordable radio telescopes developed by PrimaLuceLab with Radio2Space brand. These instruments allow any school, university, museum or science institute to make real radio astronomy with powerful but affordable, compact and easy to use radio telescopes.