What is recorded here?
Hubble organized extragalactic systems by photographic structure: elliptical images, normal and barred spirals, and irregular forms. The 1926 paper details a morphological classification developed from earlier photographs. A consistent vocabulary makes large populations comparable. Spiral structure, bars and apparent ellipticity define different classes, with orientation and uncertain cases limiting interpretation. This observational scheme is a separate contribution from the later velocity–distance analysis.
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Scientific scope
This is a descriptive classification of projected images. Early and late type names do not establish an evolutionary sequence. The paper's historical luminosity and distance assumptions are not adopted here.
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People and systems
Edwin Hubble
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English catalogue narrative
Hubble: a photographic classification of galaxies
Hubble organized extragalactic systems by photographic structure: elliptical images, normal and barred spirals, and irregular forms. The 1926 paper details a morphological classification developed from earlier photographs.
A consistent vocabulary makes large populations comparable. Spiral structure, bars and apparent ellipticity define different classes, with orientation and uncertain cases limiting interpretation. This observational scheme is a separate contribution from the later velocity–distance analysis.
Scientific scope
This is a descriptive classification of projected images. Early and late type names do not establish an evolutionary sequence. The paper's historical luminosity and distance assumptions are not adopted here.
People and systems
Edwin Hubble