Classification of the Milky Way Galaxy

Our Galaxy is classified as Sb (Sky Catalogue 2000.0) or Sbc by most sources. Newer investigations have brought up more and more evidence that the Milky Way probably has a bar, or barlike structure, in its central region, which would modify its classification to become a barred spiral of type SB, or intermediate type between barred and "normal" spirals, SAB. Recent investigations have brought up evidence that our Galaxy may even have a pronounced bar structure measuring as much as 27,000 light-years in length.

Already in the 1970s, Gerard de Vaucouleurs has classified the Milky Way Galaxy as "SAB(rs)bc II," where

"SAB" means that the Milky Way has (probably) a less evolved central bar structure - "SA" would be a "normal", barless spiral, "SB" a barred spiral galaxy
"(rs)" means that there is a weak central ring of stars and gas around the nucleus
"bc"

The new results may change this classification to "SB(rs)bc II."

Hartmut Frommert
Christine Kronberg
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Last Modification: August 26, 2005