- Stellar populations
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▪ TableStellar populationsPopulation I disk population Population IIextremePopulation I olderPopulation I intermediatePopulation II haloPopulation IImembers gas A-type stars stars of galactic nucleus high-velocity stars with z-velocities >30 km/sec subdwarfsyoung stars associated with the present spiral structure strong-line stars planetary nebulae (planetary nebula) long-period variables with periods <250 days and spectral types earlier than M5e globular clusters (globular cluster)supergiants Me dwarfs novae (nova) RR Lyrae stars (RR Lyrae star) with periodsCepheids (Cepheid variable) RR Lyrae stars with periods<0.4 daysT Tauri stars (T Tauri star) weak-line starsgalactic clusters of Trumpler's class Iaverage height over galactic plane (parsecs) 120 160 400 700 2,000average velocity perpendicular to galactic plane z(km/sec) 8 10 17 25 75axial ratio of spheroidal distribution 100 ? 25? 5 2concentration toward centre little little strong? strong strongdistribution extremely patchy; spiral arms patchy; spiral arms smooth? smooth smoothage (109 years) 0.1 0.1–1.5 1.5–5.0 5.0–6.0 6total mass(109 suns) 2 5 47 (combined disk and intermediate Population II) 16See as table:
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Universalium. 2010.