Artist's Concept of Milky Way vs Galaxy MACS2129-1
This artist's concept shows what the young, dead, disk galaxy MACS2129-1, right, would look like when compared with the Milky Way galaxy, left. Although three times as massive as the Milky Way, it is only half the size. MACS2129-1 is also spinning more than twice as fast as the Milky Way. Note that regions of Milky Way are blue from bursts of star formation, while the young, dead galaxy is yellow, signifying an older star population and no new star birth.