Galaxy Wars: M81 Versus M82 . ... Credit Copyright: Robert Gendler Explanation: In the left corner, wearing a red nucleus surrounded by blue spiral arms, is M81 . In the right corner, sporting light stars and dark dust lanes, is M82 . These two mammoth galaxies have been locked in gravitational combat for the past billion years. ... Last go-round, M82's gravity likely raised circulating density waves rippling around M81 resulting in the richness of M81 's spiral arms. ...