An example o a spiral galaxy, the Pinwheel Galaxy (an aa kent as Messier 101 or NGC 5457)

A spiral galaxy is a certain kynd o galaxy originally describit bi Edwin Hubble in his 1936 wirk The Realm of the Nebulae[1] an, as such, forms pairt o the Hubble sequence.


  1. Hubble, E.P. (1936). The realm of the nebulae (PDF). Mrs. Hepsa Ely Silliman memorial lectures, 25. New Haven: Yale University Press. ISBN 9780300025002. OCLC 611263346. Archived frae the oreeginal on 2012-09-29.(pp. 124–151)