Part One I › Division III III › Section 132 132

Galaxies and Stars

Subject Outline

AGalaxies in general
- 1Statistical properties
  - aClassification of galaxies
  - bObservational methods of determining the distances to galaxies
  - cDistribution of galaxies
- 2Physical properties: size, mass, luminosity, age, composition
- 3Structural features
- 4Clusters of galaxies
  - aTypes and distribution
  - bInteractions between cluster members
- 5Extragalactic radio and X-ray sources
  - aRadio galaxies
  - bX-ray galaxies
  - cQuasars
- 6The origin and evolution of the galaxies [see also 131.E.2.]
BThe Galaxy: the Milky Way system
- 1Distance determinations in the Galaxy
- 2Stellar velocities: the motions of stars with respect to the Sun, the motion of the Sun with respect to the Local Standard of Rest (lsr)
- 3The stars and star clusters nearest the Sun
- 4The classification of stars according to the Hertzsprung-Russell diagram
- 5The galactic composition
  - aThe stellar populations
  - bEmission nebulae: composition and physical characteristics of H II regions
  - cPlanetary nebulae
  - dSupernova remnants
  - eDust clouds
  - fThe general interstellar medium: principal components and their distribution throughout the various galactic regions
    - iGrains of interstellar dust
    - iiInterstellar clouds of neutral hydrogen (H I regions)
    - iiiInterstellar molecules and radicals
  - gPrimary cosmic rays
  - hInterstellar magnetic fields
- 6Structure and dynamics of the Galaxy
  - aThe spatial structure of the Galaxy: the dimensions of the Galaxy
  - bRegions of the Galaxy: the nucleus, the central bulge, the dish, the spiral arms, the spherical component, the massive halo
  - cThe magnetic field of the Galaxy: its origin and its effects on cosmic rays, radio waves, and light
  - dThe rotation of the Galaxy: the differential rotation of stars, gas about the galactic centre
- 7The evolution of the Galaxy [see also 131.E.2.]
  - aHydromagnetic and gravitational theories of the formation of spiral structure
  - bChemical evolution: the problem of the distribution of heavy elements
  - cStar formation: theories concerning the gravitational condensation of galactic dust and gas clouds
CStar clusters and stellar associations
- 1Globular clusters: systems containing many thousands to a million old stars in a symmetrical, roughly spherical form
- 2Open clusters: systems containing about a dozen to hundreds of stars, usually in an unsymmetrical arrangement
- 3Stellar associations: loose groupings containing dozens to a few hundred stars of similar spectral type and common origin
- 4Relationship of clusters to the Galaxy: the formation and dispersion of clusters and their locations in the Galaxy
- 5Clusters in external galaxies
DStars
- 1The identification and nomenclature of the stars
  - aThe celestial sphere and celestial coordinate systems
  - bThe constellations and other sky divisions
  - cStar names and designations
  - dModern star maps and catalogs
- 2Observable stellar characteristics
  - aStellar positions and motions
  - bThe apparent brightness or apparent luminosity of the stars: the ubv and other systems
  - cStellar spectra [see also 111.C.]
- 3Derived, or calculated, stellar characteristics
  - aIntrinsic stellar brightness: absolute magnitudes, total luminosities
  - bStellar masses
  - cStellar diameters
  - dStellar temperatures
  - eThe average characteristics of main-sequence, or dwarf, stars
- 4Stellar variability
  - aGeometric variables; e.g., eclipsing binaries
  - bIntrinsic variables
    - iPulsating stars; e.g., Cepheid, RR Lyrae, and Beta Canis Majoris variables
    - iiExplosive variables; e.g., novae, supernovae, and novalike variables
- 5Statistics of stars
  - aCorrelations between luminosity, spectrum, mass, and radius: the Hertzsprung-Russell diagram and other relations
  - bStatistics of binary star systems
  - cStatistics of special types of stars
- 6Stellar structure
  - aStellar atmospheres
  - bInternal structure of stars
- 7Stellar evolution [see also 131.E.2.]
  - aThe life history of a typical star
    - iFormation of a protostar by gravitational contraction
    - iiAttainment of the main sequence
    - iiiEvolution away from the main sequence
    - ivEstimates of stellar ages
  - bFormation of chemical elements in stars