15.3 Classification of stars

15.3.1 Classification by luminosity  Relation between brightness and apparent magnitude
15.3.2 Apparent magnitude, Relation between intensity and apparent magnitude
Measurement of
m from photographic plates and distinction between
photographic and visual magnitude not required
15.3.3 Absolute magnitude,

Powerpoint demo: Astronomical distance m, M and the parsec

Parsec and light year
Definition of M, relation to
m

m M = 5 log d
                    10

15.3.4 Classification by temperature, black body radiation

powerpoint

Stefan’s law and Wien’s displacement law
General shape of black body curves, experimental verification is not
required
Use of Wien’s displacement law to estimate black-body temperature
of sources

λ max T = constant = 0.0029 mK

Inverse square law, assumptions in its application
Use of Stefan’s law to estimate area needed for sources to have same
power output as the sun

  P =  σ AT4

Assumption that a star is a black body
Problem of detector response as a function of wavelength and
atmospheric effects

15.3.5 Principles of the use of stellar spectral classes

 

Description of the main classes, O B A F G K M
Temperature required: need for excitation
Helium absorption (O): need for higher temperature
Hydrogen Balmer absorption lines (B, A): need for atoms in n=2
state
Metals absorption (F, G): occurs at lower temperature
Molecular bands (K, M): occur at lowest temperature
15.3.6 The Hertzsprung- Russell diagram

power point link to stellar evidence

multi-choice on the lifecycle of stars

General shape: main sequence, dwarfs and giants
Stellar evolution: path of a star similar to our Sun on the
Hertzsprung- Russell diagram from formation to white dwarf
15.3.7 Supernovae, neutron stars and black holes

PowerPoint - right mouse click and choose "save as"

 

General properties
Calculation of the radius of the event horizon for a black hole

Schwarzchild radius 
(Rs)

R» 2GM
          c2

15.4 Cosmology

15.4.1 Doppler effect

PowerPoint - right mouse click and choose "save as"

Df   =     and  Dλ  =  -v
 f         c            λ        c
for v « c applied to optical and radio frequencies
Calculations on binary stars viewed in the plane of orbit
15.4.2 Hubble’s law

example
doppler shift question

Red shift

 v = Hd

Simple interpretation as expansion of universe; estimation of age of universe, assuming H is constant
Qualitative treatment of Big Bang theory

15.4.3 Quasars Quasars as the most distant measurable objects
Discovery as bright radio sources
Controversy concerning distance and power – use of inverse square
law
Quasars show large optical red shifts; estimation of distance

Revision Resources 

Glossary - unfinished - based on last year's syllabus

Another Glossary

PH04 past module exam questions March2000, Feb96 & March97