M.A.Burleigh 2601/Unit 6

DEPARTMENT OF PHYSICS AND ASTRONOMY

LIFECYCLES OF STARSLIFECYCLES OF STARS

Option 2601Option 2601

M.R. Burleigh 2601/Unit 6

Stellar PhysicsStellar Physics

Unit 1 - Observational properties of Unit 1 - Observational properties of starsstars

Unit 2 - Stellar SpectraUnit 2 - Stellar Spectra Unit 3 - The SunUnit 3 - The Sun Unit 4 - Stellar StructureUnit 4 - Stellar Structure Unit 5 - Stellar EvolutionUnit 5 - Stellar Evolution Unit 6 - Stars of particular interestUnit 6 - Stars of particular interest

M.A.Burleigh 2601/Unit 6

DEPARTMENT OF PHYSICS AND ASTRONOMY

Unit 6Unit 6

Particularly Interesting StarsParticularly Interesting Stars

M.R. Burleigh 2601/Unit 6

Particularly Interesting StarsParticularly Interesting Stars

Binaries – visual, spectroscopic, Binaries – visual, spectroscopic, eclipsingeclipsing

Variable starsVariable stars Active/interacting binaries (Novae)Active/interacting binaries (Novae) Stellar pulsationsStellar pulsations Cepheid variables and the distance Cepheid variables and the distance

scalescale

M.R. Burleigh 2601/Unit 6

ApparentApparent Stars not physically associated but lie Stars not physically associated but lie close together along the line of sightclose together along the line of sight

VisualVisual Stars can be resolvedStars can be resolved

AstrometricAstrometric Only one star visible but its motion on Only one star visible but its motion on the sky reveals an unseen companionthe sky reveals an unseen companion

SpectroscopicSpectroscopic Unresolved system, see periodic Unresolved system, see periodic shifts/broadening of spectral linesshifts/broadening of spectral lines

SpectrumSpectrum No movement of spectral features but No movement of spectral features but two different spectral signatures two different spectral signatures visiblevisible

EclipsingEclipsing Brightness changes as one star Brightness changes as one star passes in front of the otherpasses in front of the other

Types of binary systemTypes of binary system

M.R. Burleigh 2601/Unit 6

Spectroscopic BinariesSpectroscopic Binaries

M.R. Burleigh 2601/Unit 6

Eclipsing BinariesEclipsing Binaries

M.R. Burleigh 2601/Unit 6

Eclipsing BinariesEclipsing Binaries

M.R. Burleigh 2601/Unit 6

M.R. Burleigh 2601/Unit 6

Information from Binary SystemsInformation from Binary Systems

Masses of componentsMasses of components Dimensions of components (particularly Dimensions of components (particularly

in eclipsing systems)in eclipsing systems) Physical characteristics of systemsPhysical characteristics of systems

M.R. Burleigh 2601/Unit 6

(Other) Variable Stars(Other) Variable Stars

Intrinsic variables… i.e. pulsating starsIntrinsic variables… i.e. pulsating stars Geometric (extrinsic) variables… i.e. Geometric (extrinsic) variables… i.e.

eclipsing systemseclipsing systems Naming variables… constellation & Naming variables… constellation &

letters beginning with Rletters beginning with R– R…. To Z, then RR…. To ZZ (i.e. R CrB)R…. To Z, then RR…. To ZZ (i.e. R CrB)– Then Vijk constellation (i.e. V471 Tau)Then Vijk constellation (i.e. V471 Tau)

M.R. Burleigh 2601/Unit 6

Accretion in BinariesAccretion in Binaries

M.R. Burleigh 2601/Unit 6

NovaeNovae

M.R. Burleigh 2601/Unit 6

NovaeNovae

Brightness increases by 10 magnitudes Brightness increases by 10 magnitudes during outburstduring outburst

Rise time 2-3 daysRise time 2-3 days Gradual decline over months (fast Gradual decline over months (fast

novae) or years (slow novae)novae) or years (slow novae) Material ejected with velocities up to Material ejected with velocities up to

~2000km s~2000km s-1-1

Explosions can repeat (recurrent novae)Explosions can repeat (recurrent novae)

M.R. Burleigh 2601/Unit 6

Nova Cassiopeiae 1993 light curve (first 3 months)

M.R. Burleigh 2601/Unit 6

Nova Cassiopeiae 1993 light curve (first 2½ years)

M.R. Burleigh 2601/Unit 6

Nova Cassiopeiae 1995 light curve

M.R. Burleigh 2601/Unit 6

M.R. Burleigh 2601/Unit 6

Pulsating StarsPulsating Stars

Pulsating stars are not in hydrostatic Pulsating stars are not in hydrostatic equilibriumequilibrium

Star is partially ionized at some critical Star is partially ionized at some critical depthdepth

Degree of ionization sensitive to small Degree of ionization sensitive to small temperature changestemperature changes

Small perturbation can be “amplified”Small perturbation can be “amplified”

M.R. Burleigh 2601/Unit 6

Phase

MAX. COMPRESSION

Max. opacity & ionisation, min.

photon fluxEXPANSION

Max. expansion

rate

COMPRESSION

Max. compression

rate

MAX. EXPANSION

Min. opacity & ionisation, max.

photon flux

Pressure driving

Gravity (restoring

force)

Cycle of a pulsating star

M.R. Burleigh 2601/Unit 6

TypeType PrototypePrototype MMVV Spectral Spectral classclass

Pulsation Pulsation period period rangerange

CharacterisCharacteristic periodtic period

PopulationPopulation

Classical Classical CepheidsCepheids

CepheiCephei -0.5 to –6-0.5 to –6 F6 to K2F6 to K2 11dd to 50 to 50dd 55dd to 10 to 10dd II

Population Population II Cepheids II Cepheids (W Virginis)(W Virginis)

W VirginisW Virginis 0 to –30 to –3 F2 to G6F2 to G6 22dd to 45 to 45dd 1212dd to 28 to 28dd IIII

RR Lyrae RR Lyrae starsstars

RR LyraeRR Lyrae 0.5 to 10.5 to 1 A2 to F6A2 to F6 1.51.5hh to 24 to 24hh 0.50.5dd IIII

Long-period Long-period variables variables (Mira)(Mira)

CetiCeti 1 to –21 to –2 M1 to M6M1 to M6 130130dd to 500 to 500dd 270270dd DiskDisk

RV Tauri RV Tauri starsstars

RV TauriRV Tauri -3-3 G, KG, K 2020dd to 150 to 150dd 7575dd IIII

Beta Canis Beta Canis Majoris Majoris starsstars

Canis Canis MajorisMajoris

-3-3 B1, B2B1, B2 44hh to 6 to 6hh 55hh II

Semiregular Semiregular red red variablesvariables

HerculisHerculis -1 to –3-1 to –3 K, M, R, N, K, M, R, N, SS

100100dd to 200 to 200dd 100100dd I and III and II

Dwarf Dwarf CepheidsCepheids

ScutiScuti 4 to 24 to 2 A to FA to F 11hh to 3 to 3hh 22hh II

M.R. Burleigh 2601/Unit 6

H-R diagram for pulsating starsH-R diagram for pulsating stars

M.R. Burleigh 2601/Unit 6

Typical Cepheid light curve

Cepheid VariablesCepheid Variables

M.R. Burleigh 2601/Unit 6

Cepheid VariablesCepheid Variables

M.R. Burleigh 2601/Unit 6

Cepheid VariablesCepheid Variables

M.R. Burleigh 2601/Unit 6

The period-luminosity relation for Cepheids

M.R. Burleigh 2601/Unit 6

RedshiftRedshift

Edwin Hubble discovers galaxies are Edwin Hubble discovers galaxies are receding from us (c. 1930)receding from us (c. 1930)

Hubbles Law - speed increases with Hubbles Law - speed increases with distancedistance

Expansion of the Universe - Big Bang Expansion of the Universe - Big Bang theorytheory

M.R. Burleigh 2601/Unit 6

Cepheids in M100Cepheids in M100

M.R. Burleigh 2601/Unit 6

Beyond M100Beyond M100

M.A.Burleigh 2601/Unit 6

DEPARTMENT OF PHYSICS AND ASTRONOMY

Unit 6Unit 6

Particularly Interesting StarsParticularly Interesting Stars

M.R. Burleigh 2601/Unit 6

Particularly Interesting StarsParticularly Interesting Stars

Binaries – visual, spectroscopic, Binaries – visual, spectroscopic, eclipsingeclipsing

Variable starsVariable stars Active/interacting binariesActive/interacting binaries Stellar pulsationsStellar pulsations Cepheid variables and the distance Cepheid variables and the distance

scalescale

M.R. Burleigh 2601/Unit 6

Stellar PhysicsStellar Physics

Unit 1 - Observational properties of Unit 1 - Observational properties of starsstars

Unit 2 - Stellar SpectraUnit 2 - Stellar Spectra Unit 3 - The SunUnit 3 - The Sun Unit 4 - Stellar StructureUnit 4 - Stellar Structure Unit 5 - Stellar EvolutionUnit 5 - Stellar Evolution Unit 6 - Stars of particular interestUnit 6 - Stars of particular interest

M.A.Burleigh 2601/Unit 6

DEPARTMENT OF PHYSICS AND ASTRONOMY

LIFECYCLES OF STARSLIFECYCLES OF STARS

Option 2601Option 2601