Hubble type
Also called: galaxy classification, Hubble sequence, morphological type.
A short code for a galaxy's shape: E for elliptical, S0 for lenticular, Sa–Sd for spirals (SB if barred), Irr for irregular.
Edwin Hubble sorted galaxies by appearance in 1926, and his scheme is still in use. Ellipticals run from E0 (round) to E7 (elongated). Spirals run from Sa (big bulge, tightly wound arms) to Sd (small bulge, loose, ragged arms), with a B added for barred spirals — SBb, say. S0 galaxies have a disk but no arms; irregulars (Irr) have no clear shape.
In AstroPilot
Object pages list the Hubble type under the size of each galaxy.