John Reynolds: Morphologist Extraordinaire

Hubble recognized three principal form families, and placed galaxies into one of three principal classes: there were elliptical galaxies, spiral galaxies and those with a rather chaotic optical appearance, known as irregular galaxies. Spiral galaxies themselves were separated into two separate families, the normal spirals and those with a central elongated feature, the barred spirals (Figure 111).

The recognition of a bar in spiral galaxies belongs to Heber D. Curtis. Curtis had recognized a class of spirals called the phi-type spirals, but Hubble later suggested that the Greek letter theta better represented this form. To be fair to Hubble, he did consider Curtis' classification to be “easily the most significant that has been proposed up to date [1922] …” The Curtis phi-class was fully recognized in Hubble's final classification system, but Hubble used the terminology of barred spirals instead. Full credit must be given to the great observer Heber Curtis, for being the first astronomer to recognize bars in spiral galaxies.