AST 1002 Lecture Notes - Lecture 16: Virgo Supercluster, Vesto Slipher, Dark Matter
Document Summary
Chapters 15 & 16: normal galaxies and cosmic expansion (cid:862)hu(cid:271)(cid:271)le ultra deep field(cid:863): pi(cid:272)ture sho(cid:449)i(cid:374)g us (cid:374)u(cid:373)erous gala(cid:454)ies, allo(cid:449)i(cid:374)g us to de(cid:272)ipher the for(cid:373)atio(cid:374) of the universe. Galaxies come in many sizes and shapes, and tend to be in clusters. In 1924, edwin hubble classified galaxies based on their appearances: spirals: s, barred spirals: sb, elliptical: e. Spiral galaxies are subdivided: sa: large central bulge, sb: medium bulge, sc: small bulge. Barred spiral galaxies have central, bar-like structures. They are subdivided: sba: large central bulge, sbb: medium bulge, sbc: small bulge. Shapes: disks, bulges, spherical halos, sometimes bars. Stellar content: disks contain young and old stars, halos contain only old stars. Gas and dust: disk contains substantial gas and dust, halos contain neither. Star formation: ongoing star formation in disk (spiral arms) Stellar motion: circular orbits in disk, random orbits in halo. Have spheroidal shapes, with on evidence of spiral structure.
