Barred spiral galaxies have active star formation sites in arms close to a bulge. Hubble classified galaxies based on shape, with Sa galaxies having large central bulges. Nearby spiral galaxies often exhibit a barred spiral structure.
Barred spiral galaxies have arms that contain sites of active star formation and start close to a bulge in the center. For example, the strongly barred spiral galaxy NGC 1365 exhibits two main spiral arms that are populated with blue stars and red patches of glowing gas, indicating recent star formation.
Hubble classified galaxies by shape, designating Sa for galaxies with large central bulges and faint arms. These galaxies may appear lens-like with no clear spiral arm structure, resembling lenticular galaxies that share properties with elliptical galaxies.
About two-thirds of nearby spiral galaxies are barred spirals, characterized by boxy or peanut-shaped bars of stars running through their centers.
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