Hubble Images a Classic Spiral  – NASA Science

NGC 3430’s distinct shape may be one reason why astronomer Edwin Hubble used to it to help define his classification of galaxies. Namesake of the Hubble Space Telescope, Edwin Hubble authored a paper in 1926 that outlined the classification of some four hundred galaxies by their appearance — as either spiral, barred spiral, lenticular, elliptical, or irregular. This straightforward typology proved extremely influential, and the detailed schemes astronomers use today are still based on Edwin Hubble’s work. NGC 3430 itself is a spiral lacking a central bar with open, clearly defined arms — classified today as an SAc galaxy.