In 2008, infrared observations with the [[Spitzer Space Telescope]] showed that the Carina–Sagittarius Arm has a relative paucity of young stars, in contrast with the Sagittarius[[Scutum-Centaurus andArm]] Normaand spiral[[Perseus armsArm]]. This suggests that the SagittariusCarina–Sagittarius Arm is a minor arm, along with the [[Norma Arm]] (Outer Arm). These two appear to be mostly concentrations of gas, sparsely sprinkled with pockets of newly formed stars.<ref name=Churchwell2009/><ref>{{cite news |first=David |last=Shiga |authorlink= |title=Two of the Milky Way's spiral arms may be 'demoted' |url=https://www.newscientist.com/article/dn14057-two-of-the-milky-ways-spiral-arms-may-be-demoted.html |work=NewScientist |publisher= |date=2008-06-03 |accessdate=2009-09-08 }}</ref>
