Astronomy 106.02 Review


This review is organized by topic -- an organization which roughly, though not exactly follows the chapter organization in the text. You will also find useful the reviews for the three previous exams:

Exam 1

Exam 2

Exam 3

Solutions to the three exams will be available Friday, May 2. (I apologize that illness followed by my travel to a scientific conference have kept me from getting these out earlier.) Main Topics:

I. Distances and magnitudes: distances; magnitudes

II.Coordinates and timekeeping: horizon, equatorial, galactic

III.History: ancient Greece to Einstein

IV.Light: spectra, Doppler shift, etc.

V.Telescopes: optical, radio, space

VI.Sun and stars: the sun, fusion, binaries

VII.Stellar evolution: H-R diagram, supernovae

VIII.Clusters: open, globular, associations

IX.Compact objects: neutron stars & black holes

X.Milky Way: size, age, components

XI.Other galaxies: classification, active, quasars

XII.Cosmology: Olber's paradox, big bang


I. Distances and magnitudes: distances; magnitudes

Distances

(Chapter 1) Distance scales:
(Appendix A) earth-moon 3.8 X 10⁸ m
earth-sun 1.5 X 10⁸ m = 1 A.U.
light year (l.y.) 9.5 X 10¹⁵ m
parsec (pc) 3.26 l.y. = 206,000 A.U.
megaparsec (MPc) 106 pc

Distance determination:
(Section 9-1) parallax and proper motion
(Section 9-2) comparing apparent and absolute magnitude
(Section 13-4) Cepheid and Lyra variables
(Section 17-2) galactic distance indicators

Magnitudes

(Section 2-1) apparent magnitude scale (larger m means fainter)
(Section 9-2) absolute magnitude and luminosity
(Section 9-3) luminosity classification


II.Coordinates and timekeeping: horizon, equatorial, galactic

Coordinates

(Section 2-1) Constellations
(Section 2-2) Celestial sphere
horizon coordinates: altitude and azimuth
equatorial coordinates: R.A. and declination
celestial equator and celestial poles
(Section 2-2) Precession
(Section 2-3) Ecliptic, seasons, equinoxes
(Section 16-1) Galactic coordinates

III.History: ancient Greece to Einstein

Archaeoastronomy

(Section 4-1) Stonehenge, ancient Egyptians and Babylonians

Ancient Greek

(Section 4-1) Contributions of Eratosthenes, Pythagoras and others
Circular motion, parallax, mythology
(Section 4-1) Ptolemy's geocentric universe

The Golden Age of Astronomy

(Section 4-2) Copernicus' heliocentric universe
(Section 4-2) Galileo:
telescopic observations of Venus, Jupiter
defense of Copernicus
(Section 4-3) Tycho Brahe's observations
Kepler's Laws of Planetary Motion
(Section 5-1) Newton's Laws of Motion
(Section 5-2) Newton's explanation for Kepler's Laws
Escape velocity

Modern Astronomy

(Section 16-1) Determination of the size of the Milky Way
(Section 5-3) Albert Einstein: special and general relativity


IV.Light: spectra, Doppler shift, etc.

Electromagnetic spectrum

(Section 6-1) Types of light:
radio, infrared, visible, ultra-violet, x-ray, gamma-ray
light as a photon or as a wave

Spectrum as a measure of temperature

(Section 7-1) Black-body spectrum peak depends on temperature
(Section 7-4) Spectral classification: O B A F G K M

Atoms and the production of spectral lines

(Section 7-2) Atoms consist of nuclei (protons & neutrons) and electrons
Ions are non-neutral atoms
(Section 7-3) Excitation of electrons produce spectral lines
Emission spectra: bright lines from hot gases
Absorption spectra: dark lines from cooler gases
(Section 7-4) Spectra tell what elements are present
(Section 11-2) Elements in nebulae and molecular clouds
(Section 16-2) Different metallicity of different galactic populations

Doppler shift

(Section 7-4) Doppler shift explained
red shift for receding, blue shift for approaching
(Section 17-2) Hubble relation involves red shift
(Section 19-1) Hubble relation suggests an expanding universe


V.Telescopes: optical, radio, space

Optical telescopes

(Section 6-2) Refracting and reflecting
Schmidt-Cassegrain (Hampden-Sydney telescope)
Powers of a telescope:
light-gathering, resolving, magnifying
(Perspective) Hubble Space Telescope

Radio telescopes

(Section 6-3) Individual and arrays of telescopes
high resolution available with radio telescope

Space telescopes

(Section 6-4) x-ray telescopes
gamma-ray telescopes
(Compton Gamma-Ray Observatory)


VI.Sun and stars: the sun, fusion, binaries

Features of the sun

(Data File I) Solar properties:
radius: 7 X 10⁵ km
mass: 2 X 10³⁰ kg
luminosity: 3.8 X 10²⁶ J/s
surface temperature: 5800 K
rotation period: ~25 days
(Section 8-1) Solar layers: photosphere, chromosphere, corona
Solar wind
(Section 8-2) Sunspots
Solar magnetic field
Prominences and flares
Nuclear fusion

(Section 12-2) Hydrogen fusion in the sun and other stars
Energy transport: conduction, convection, radiation
Hydrostatic equilibrium:
radiation pressure vs. gravitation
Stellar features

(Section 10-4) Stellar mass and density
(Section 10-4) Mass-luminosity relationship

Binary stars

(Section 10-1) Visual binaries
Astrometric binaries: only one star is seen
(Section 10-2) Spectroscopic binaries
(Section 10-3) Eclipsing binaries: light curves


VII.Stellar evolution: H-R diagram, supernovae

H-R diagram

(Section 9-3) Luminosity vs. temperature
Main sequence, giants and white dwarves

Formation of stars

(Section 11-1) Interstellar medium
Emission nebulae glow on their own: H-II regions
Reflection nebulae shine from embedded bright stars
Dark nebulae contain dust
(Section 11-2)Molecular clouds
(Section 12-4) Orion Nebula
(Section 12-1) Birth of stars: protostars and pre-main sequence stars

Life on the Main Sequence

(Section 13-1) Mass vs. luminosity, mass vs. lifetime
(Section 14-1) Red dwarves (M < 0.4 Mo) never become giants

Post-Main sequence evolution

(Section 13-2) Fusion of helium and heavier elements
Expansion into a red giant
(Section 14-1) Loss of material to a planetary nebula
Contraction into a white dwarf
(Section 14-2) Evolution of heavier stars (M > 4Mo)
Fusion of elements up to iron
Supernova explosions: Type I and II
(Section 16-2) Recyling of stellar material by supernovae


VIII.Clusters: open, globular, associations

Types of clusters

(Section 13-3) Open clusters: 10-10,000 stars in 25 pc region
Globular clusters: 10⁵ - 10⁶ stars in 10-30 pc region
(Section 16-1) Associations: groups of stars not gravitationally bound

Clusters used to study stellar evolution

(Section 13-3) Cluster stars are about the same distance and age
Turn-off point from the Main Sequence

Clusters used to study the Milky Way

(Section 16-1) Globular clusters located mostly in the galactic halo


IX.Compact objects: neutron stars & black holes

White dwarves

(Section 14-1) Properties of white dwarves
Density: 3 X 10⁶ g/cm²
Radius: about the size of the earth
No energy source; like a glowing ember
Eventually burn out to become black dwarves

Neutron stars

(Section 15-1) Properties of neutron stars
Density: 10¹⁴ g/cm²
Radius: 10-15 km
Rapid rotation
Large magnetic fields
Supported by neutron degeneracy pressure
Pulsars are neutron stars:
"pulses" are due to the lighthouse effect
Pulsars eventually lose energy and slow down
Binary pulsars show evidence of gravity waves

Black holes

(Section 15-2) Escape velocity larger than the speed of light
Infinite density; no force to oppose gravity
Properties: charge, mass, angular momentum
Event horizon is point of no return
Schwarzschild (non-rotating) and Kerr (rotating)
Evidence for black holes in binary systems


X.Milky Way: size, age, components

Properties

(Section 16-1) Diameter: 30-40 kpc
Sun located 8.5 kpc from the center
Mass: 10¹⁰ solar masses
Variable rotation: sun's rotation period 2.4 X 10⁶ years

Components

(Section 16-1) Spiral arms contain mostly young stars (Extreme Pop I)
Disk (Intermediate Pop I)
Nuclear bulge: medium age stars (Intermed Pop II)
Halo: oldest stars in globular clusters (Extreme Pop II)
Possible galactic corona

Theories of the origin of the spiral arms

(Section 16-3) Density wave theory
Self-sustaining star formation theory

Galactic center

(Section 16-4) Large amounts of energy coming from a small region
Possible massive black hole in the galactic center


XI.Other galaxies: classification, active, quasars

Classification

(Section 17-1) Elliptical: E0-E9
most numerous, contain mostly older stars
Spiral Sa-Sc, SBa-SBc
brightest, contain more young stars
Irregular

Collision of galaxies

(Section 17-3) Evidence seen in interacting pairs of galaxies

Clusters of galaxies

(Section 16-3) Local cluster, Virgo cluster, etc.
Superclusters contain several clusters
Walls, filaments and voids are the largest structures

Active galaxies (AGNs)

(Section 18-1) Radio lobes are huge and contain much energy
Jets supply lobes with matter
Large black holes are most likely located at the center
Radio lobes interact with the intergalactic medium

Quasars

(Section 18-2) Quasi-stellar objects appear small
Very distant, luminous, and old
Probably the same energy source as AGNs
Show evidence of gravitational lensing


XII.Cosmology: Olber's paradox, big bang

Olber's paradox and its resolution

(Section 19-1) Why is the sky dark?
The universe is not infinite and has not existed forever

Current cosmological assumptions

(Section 19-1) Homogeneity, isotropy, universality

Observational evidence for the big bang

(Section 19-1) Hubble relation indicates an expanding universe
(Section 19-2) Age of the universe is ~ 1/H
(Section 19-2) Cosmic background radiation

History of the big bang

(Section 19-2) Expansion from a singularity
Formation of particles in the first three minutes
Recombination (decoupling) and formation of atoms

Closed vs. open universe

(Section 19-2) Closed universe would eventually collapse
Open universe would expand forever
Which choice depends on how much mass there is
Observations cannot decide between open or closed

Problems with the big bang model

(Section 19-3) flatness, isotropy, structure
inflation in the early universe helps solve the problem