Edwin Hubble Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time. Hubble discovered that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. He used the strong direct relationship between a classical Cepheid variable's luminosity and pulsation period (discovered in 1908 by Henrietta Swan Leavitt) for scaling galactic and extragalactic distances. Hubble provided evidence
Lyon-Meudon Extragalactic Database Lyon-Meudon Extragalactic Database The Lyon-Meudon Extragalactic Database (LEDA) was a database of galaxies, created in 1983 at the Lyon Observatory. Each galaxy had a number assigned to it, which is now known as its PGC number. The Principal Galaxies Catalogue (PGC), published in 1989, was based on the Lyon-Meudon Extragalactic Database and contained cross-identifications for it. LEDA was eventually merged with Hypercat to become HyperLEDA in 2000, itself also known as PGC2003. LEDA originally contained information on more than 60 parameters for about 100,000 galaxies, and now contains information on over 3 million celestial objects, of which about 1.5 million