Edwin Hubble, and others. Edwin Hubble discovered that most nebulae are associated with stars and illuminated by starlight. He also helped categorize nebulae based on the type of light spectra they produced.

Observational history

Around 150 AD, Ptolemy recorded, in books VII-VIII of his Almagest, five stars that appeared nebulous. He also noted a region of nebulosity between the constellations

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