A100–Exploring the : More stellar properties

Martin D. Weinberg UMass Astronomy [email protected]

October 23, 2012

Read: Chap 15, 16, S4 10/23/11 – slide 1 Announcements

⊲ Announcements Orchard Hill public observing. HR diagram http://www.astro.umass.edu/orchardhill, for MS explanation Review schedule info Sizes of Off the MS Variable stars Pulsations Cepheids clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 2 Announcements

⊲ Announcements Orchard Hill public observing. HR diagram http://www.astro.umass.edu/orchardhill, for MS explanation Review schedule info Sizes of stars Off the MS Variable stars Tutorial mechanics Pulsations Cepheids Lecture on Telescopes moved to 20 November Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 2 Announcements

⊲ Announcements Orchard Hill public observing. HR diagram http://www.astro.umass.edu/orchardhill, for MS explanation Review schedule info Sizes of stars Off the MS Variable stars Tutorial mechanics Pulsations Cepheids Lecture on Telescopes moved to 20 November Star clusters Ages of star clusters Testing theory Others? Today: More stellar properties QM uncertainty QM uncertainty ⊲ The H-R diagram Degeneracy in stars Low-mass evolution ⊲ Pulsating stars Thought question Post MS ⊲ Star clusters Broken thermostat ⊲ Helium fusion Today: The Uncertainty Principle Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 2 Announcements

⊲ Announcements Orchard Hill public observing. HR diagram http://www.astro.umass.edu/orchardhill, for MS explanation Review schedule info Sizes of stars Off the MS Variable stars Tutorial mechanics Pulsations Cepheids Lecture on Telescopes moved to 20 November Star clusters Ages of star clusters Testing theory Others? Today: More stellar properties QM uncertainty QM uncertainty ⊲ The H-R diagram Degeneracy in stars Low-mass evolution ⊲ Pulsating stars Thought question Post MS ⊲ Star clusters Broken thermostat ⊲ Helium fusion Today: The Uncertainty Principle Thought question Helium burning Questions?

Read: Chap 15, 16, S4 10/23/11 – slide 2 The Hertzsprung-Russell Diagram

Announcements ⊲ HR diagram MS explanation Review Sizes of stars Plot the luminosity Off the MS and temperature of Variable stars Pulsations stars Cepheids Star clusters Distribution of stars Ages of star clusters does not cover the Testing theory Others? plot QM uncertainty QM uncertainty Isolated to specific Degeneracy in stars Low-mass evolution regions Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 3 Significance of the

Announcements HR diagram ⊲ MS explanation Main-sequence Review Sizes of stars stars are fusing Off the MS Variable stars into Pulsations helium in their Cepheids Star clusters cores like the Sun Ages of star clusters Testing theory Others? Luminous main- QM uncertainty sequence stars are QM uncertainty Degeneracy in stars hot (blue) Low-mass evolution Thought question Post MS Less luminous Broken thermostat Helium fusion ones are cooler Thought question (yellow or red) Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 4 Significance of the Main Sequence

Announcements High-mass stars HR diagram ⊲ MS explanation Review Sizes of stars Off the MS Variable stars Mass measure- Pulsations Cepheids ments of main- Star clusters sequence stars Ages of star clusters Testing theory show that the Others? QM uncertainty hot, blue stars QM uncertainty are much more Degeneracy in stars massive than the Low-mass evolution Low-mass stars Thought question cool, red ones Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 5 Significance of the Main Sequence

Announcements High-mass stars HR diagram ⊲ MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids The mass of a Star clusters normal, hydrogen- Ages of star clusters Testing theory burning star de- Others? QM uncertainty termines its lumi- QM uncertainty nosity and spectral Degeneracy in stars type! Low-mass evolution Low-mass stars Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 5 Significance of the Main Sequence

Announcements High-mass stars HR diagram ⊲ MS explanation Review Core pressure and Sizes of stars Off the MS temperature of a Variable stars higher-mass star Pulsations Cepheids need to be larger Star clusters in order to balance Ages of star clusters Testing theory gravity Others? QM uncertainty QM uncertainty Higher core tem- Degeneracy in stars perature boosts fu- Low-mass evolution Low-mass stars Thought question sion rate, leading Post MS Broken thermostat to larger luminos- Helium fusion ity Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 5 Stellar properties review

Announcements HR diagram Luminosity: from brightness and distance MS explanation ⊲ Review −4 6 Sizes of stars 10 LSun → 10 LSun Off the MS Variable stars Pulsations Cepheids Star clusters Temperature: from color and spectral type Ages of star clusters Testing theory → Others? 3, 000K 50, 000K QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Mass: from period (p) and average separation (a) of Thought question Post MS binary-star orbit Broken thermostat Helium fusion → Thought question 0.08MSun 100MSun Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 6 Stellar properties review

Announcements HR diagram Luminosity: from brightness and distance MS explanation ⊲ Review −4 6 Sizes of stars [0.08MSun] 10 LSun → 10 LSun [100MSun] Off the MS Variable stars Pulsations Cepheids Star clusters Temperature: from color and spectral type Ages of star clusters Testing theory → Others? [0.08MSun] 3, 000K 50, 000K [100MSun] QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Mass: from period (p) and average separation (a) of Thought question Post MS binary-star orbit Broken thermostat Helium fusion → Thought question 0.08MSun 100MSun Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 6 Mass & Lifetime

Announcements HR diagram Sun’s life expectancy: 10 billion years MS explanation ⊲ Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 7 Mass & Lifetime

Announcements HR diagram Sun’s life expectancy: 10 billion years MS explanation Hydrogen in core is exhausted (about 10% of total mass) ⊲ Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 7 Mass & Lifetime

Announcements HR diagram Sun’s life expectancy: 10 billion years MS explanation Hydrogen in core is exhausted (about 10% of total mass) ⊲ Review Sizes of stars Off the MS Variable stars Life expectancy of 10 MSun star: Pulsations Cepheids 4 ⊲ Star clusters 10 times as much fuel, uses it 10 times as fast Ages of star clusters 4 ⊲ ≈ × Testing theory 10 million years 10 billion years 10/10 Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 7 Mass & Lifetime

Announcements HR diagram Sun’s life expectancy: 10 billion years MS explanation Hydrogen in core is exhausted (about 10% of total mass) ⊲ Review Sizes of stars Off the MS Variable stars Life expectancy of 10 MSun star: Pulsations Cepheids 4 ⊲ Star clusters 10 times as much fuel, uses it 10 times as fast Ages of star clusters 4 ⊲ ≈ × Testing theory 10 million years 10 billion years 10/10 Others? QM uncertainty Life expectancy of 0.1 MSun star: QM uncertainty Degeneracy in stars ⊲ Low-mass evolution 0.1 times as much fuel, uses it 0.01 times as fast Thought question ⊲ 100 billion years ≈ 10 billion years ×0.1/0.01 Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 7 Main sequence summary

Announcements HR diagram High Mass MS explanation Review ⊲ ⊲ Sizes of stars High Luminosity Off the MS ⊲ Short-Lived Variable stars Pulsations ⊲ Large Radius Cepheids Star clusters ⊲ Blue Ages of star clusters Testing theory Low Mass Others? QM uncertainty QM uncertainty ⊲ Low Luminosity Degeneracy in stars Low-mass evolution ⊲ Long-Lived Thought question ⊲ Post MS Small Radius Broken thermostat ⊲ Red Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 8 Sizes of stars

Announcements HR diagram MS explanation Review ⊲ Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 9 Off the main sequence

Announcements HR diagram Stellar properties depend on both mass and age: MS explanation Those that have finished fusing H to He in their cores are Review Sizes of stars no longer on the main sequence ⊲ Off the MS Variable stars All stars become larger and redder after exhausting their Pulsations Cepheids core hydrogen: Star clusters giants and supergiants Ages of star clusters Testing theory Most stars end up small and white after fusion has Others? QM uncertainty ceased: QM uncertainty white dwarfs Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 10 Variable stars

Announcements Why do the properties of some stars vary??? HR diagram MS explanation Review Sizes of stars Off the MS ⊲ Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 11 Variable stars

Announcements HR diagram Some stars vary in brightness because they cannot MS explanation achieve proper balance between power welling up from Review Sizes of stars the core and power radiated from the surface Off the MS ⊲ Variable stars Such a star alternately expands and contracts, varying in Pulsations Cepheids brightness as it tries to find a balance Star clusters Ages of star clusters Any star that varies significantly in brightness with time Testing theory is called a variable star Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 12 Pulsating variable stars

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars ⊲ Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS The light curve of this pulsating variable star shows that Broken thermostat Helium fusion its brightness alternately rises and falls over a 50-day Thought question Helium burning period

Read: Chap 15, 16, S4 10/23/11 – slide 13 Cepheid variable stars

Announcements HR diagram MS explanation Review Sizes of stars Most pulsating vari- Off the MS Variable stars able stars inhabit Pulsations an instability strip ⊲ Cepheids Star clusters on the H-R diagram Ages of star clusters Testing theory Others? QM uncertainty The most luminous QM uncertainty ones are known as Degeneracy in stars Low-mass evolution Cepheid variables Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 14 Star clusters

Announcements There are two types of star clusters HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids ⊲ Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 15

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids ⊲ Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion A few thousand loosely packed stars Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 16

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids ⊲ Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Up to a million or more stars in a dense ball bound Thought question Helium burning together by gravity

Read: Chap 15, 16, S4 10/23/11 – slide 17 H-R diagram of globular cluster

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Luminosity ⊲ Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS ← Temperature Broken thermostat Messier 13 Helium fusion Thought question Ignore strange units on axes Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 18 H-R diagram of globular cluster

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids ⊲ Star clusters Ages of star clusters Superposition of many Testing theory HR diagrams Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 18 Ages of star clusters Main-sequence turnoff

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star ⊲ clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 19 Ages of clusters

Announcements HR diagram Main-sequence MS explanation turnoff point of a Review Sizes of stars cluster tells us its Off the MS Variable stars age Pulsations Cepheids To determine accu- Star clusters rate ages, we com- Ages of star ⊲ clusters pare models of stel- Testing theory Others? lar evolution to the QM uncertainty cluster data QM uncertainty Degeneracy in stars Detailed modeling Low-mass evolution Thought question of the oldest glob- Post MS ular clusters reveals Broken thermostat Helium fusion that they are about Thought question Helium burning 13 billion years old!

Read: Chap 15, 16, S4 10/23/11 – slide 20 Stellar mass and fusion

Announcements HR diagram The mass of a main sequence star determines its core MS explanation pressure and temperature Review Sizes of stars Off the MS Stars of higher mass have higher core temperature and Variable stars more rapid fusion, making those stars both more Pulsations Cepheids luminous and shorter-lived Star clusters Ages of star Stars of lower mass have cooler cores and slower fusion ⊲ clusters Testing theory rates, giving them smaller luminosities and longer Others? lifetimes QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 21 Stellar mass and fusion

Announcements High-mass stars HR diagram > 8MSun MS explanation Review Sizes of stars Off the MS Intermediate- Variable stars mass stars Pulsations Cepheids Star clusters Ages of star ⊲ clusters Low-mass stars Testing theory Others? < 2MSun QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Brown Dwarfs Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 22 Clusters and stellar lifetimes

Announcements HR diagram Our knowledge of MS explanation the life stories of Review Sizes of stars stars comes from Off the MS Variable stars comparing mathe- Pulsations matical models of Cepheids Star clusters stars with observa- Ages of star clusters tions ⊲ Testing theory Others? Star clusters are QM uncertainty QM uncertainty particularly use- Degeneracy in stars ful because they Low-mass evolution Thought question contain stars of Post MS Broken thermostat different mass that Helium fusion were born about Thought question Helium burning the same time

Read: Chap 15, 16, S4 10/23/11 – slide 23 What are giants, supergiants and white dwarfs?

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory ⊲ Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 24 The Uncertainty Principle

Announcements HR diagram The more we know about where MS explanation Review a particle is located, the less we Sizes of stars Off the MS can know about its momentum, Variable stars Pulsations and conversely, the more we know Cepheids Star clusters about its momentum, the less we Ages of star clusters Testing theory can know about its location Others? ⊲ QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 25 The Uncertainty Principle

Announcements HR diagram The more we know about where MS explanation Review a particle is located, the less we Sizes of stars Off the MS can know about its momentum, Variable stars Pulsations and conversely, the more we know Cepheids Star clusters about its momentum, the less we Ages of star clusters Testing theory can know about its location Others? ⊲ QM uncertainty QM uncertainty Degeneracy in stars In our everyday experience, a particle has a well-defined Low-mass evolution position at each moment in time Thought question Post MS But in the quantum realm particles do not have Broken thermostat Helium fusion well-defined positions Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 25 Electrons as waves

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory On atomic scales, an electron often behaves more like a Others? ⊲ QM uncertainty wave with a well-defined momentum but a poorly QM uncertainty defined position Degeneracy in stars Low-mass evolution Thought question In quantum mechanics an electron in an atom does not Post MS orbit in the usual sense Broken thermostat Helium fusion We can know only the probability of finding an electron Thought question Helium burning at a particular spot

Read: Chap 15, 16, S4 10/23/11 – slide 26 Location and momentum

Announcements HR diagram MS explanation Uncertainty Uncertainty in Planck’s Review × = Sizes of stars in location momentum Constant (h) Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty ⊲ QM uncertainty The quantum state of a particle specifies its location, Degeneracy in stars momentum, orbital angular momentum, and spin to the Low-mass evolution Thought question extent allowed by the uncertainty principle Post MS Broken thermostat Type particles (fermions) can not occupy the same Helium fusion quantum state (Pauli Exclusion Principle) Thought question Helium burning Determines atomic structure (chemistry!)

Read: Chap 15, 16, S4 10/23/11 – slide 27 Location and momentum

Announcements HR diagram MS explanation Uncertainty Uncertainty in Planck’s Review × = Sizes of stars in location momentum Constant (h) Off the MS Variable stars Pulsations Uncertainty Uncertainty in Planck’s × = Cepheids in energy Star clusters time Constant (h) Ages of star clusters Testing theory Others? QM uncertainty ⊲ QM uncertainty The quantum state of a particle specifies its location, Degeneracy in stars Low-mass evolution momentum, orbital angular momentum, and spin to the Thought question extent allowed by the uncertainty principle Post MS Broken thermostat Type particles (fermions) can not occupy the same Helium fusion Thought question quantum state (Pauli Exclusion Principle) Helium burning Determines atomic structure (chemistry!)

Read: Chap 15, 16, S4 10/23/11 – slide 27 Location and momentum

Announcements HR diagram MS explanation Uncertainty Uncertainty in Planck’s Review × = Sizes of stars in location momentum Constant (h) Off the MS Variable stars Pulsations Uncertainty Uncertainty in Planck’s × = Cepheids in energy Star clusters time Constant (h) Ages of star clusters Testing theory The Uncertainty Principle Others? QM uncertainty The quantum state of a particle specifies its location, ⊲ QM uncertainty Degeneracy in stars momentum, orbital angular momentum, and spin to the Low-mass evolution Thought question extent allowed by the uncertainty principle Post MS Broken thermostat Type particles (fermions) can not occupy the same Helium fusion quantum state (Pauli Exclusion Principle) Thought question Helium burning Determines atomic structure (chemistry!)

Read: Chap 15, 16, S4 10/23/11 – slide 27 Location and momentum

Announcements HR diagram MS explanation Uncertainty Uncertainty in Planck’s Review × = Sizes of stars in location momentum Constant (h) Off the MS Variable stars Pulsations Uncertainty Uncertainty in Planck’s × = Cepheids in energy Star clusters time Constant (h) Ages of star clusters Testing theory The Uncertainty Principle Others? QM uncertainty The quantum state of a particle specifies its location, ⊲ QM uncertainty Degeneracy in stars momentum, orbital angular momentum, and spin to the Low-mass evolution Thought question extent allowed by the uncertainty principle Post MS Broken thermostat Type particles (fermions) can not occupy the same Helium fusion quantum state (Pauli Exclusion Principle) Thought question Helium burning Determines atomic structure (chemistry!)

Read: Chap 15, 16, S4 10/23/11 – slide 27 Electron cloud

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty ⊲ QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 28 How does QM affect stars?

Thermal pressure Announcements HR diagram ⊲ MS explanation Molecules striking the walls of a container (e.g. Review balloon) apply thermal pressure that depends on the Sizes of stars Off the MS temperature inside the balloon Variable stars ⊲ Pulsations Most stars are supported by thermal pressure Cepheids Star clusters Degeneracy pressure Ages of star clusters Testing theory Others? ⊲ Laws of quantum mechanics create a different form QM uncertainty of pressure known as degeneracy pressure ⊲ QM uncertainty Degeneracy in stars ⊲ Squeezing matter restricts locations of its particles, Low-mass evolution Thought question increasing their uncertainty in momentum Post MS ⊲ But two particles cannot be in same quantum state Broken thermostat Helium fusion (including momentum) at same time Thought question Helium burning ⊲ There must be an effect that limits how much matter can be compressed: degeneracy pressure

Read: Chap 15, 16, S4 10/23/11 – slide 29 How does QM affect stars?

Thermal pressure Announcements HR diagram ⊲ MS explanation Molecules striking the walls of a container (e.g. Review balloon) apply thermal pressure that depends on the Sizes of stars Off the MS temperature inside the balloon Variable stars ⊲ Pulsations Most stars are supported by thermal pressure Cepheids Star clusters Degeneracy pressure Ages of star clusters Testing theory Others? ⊲ Laws of quantum mechanics create a different form QM uncertainty of pressure known as degeneracy pressure ⊲ QM uncertainty Degeneracy in stars ⊲ Squeezing matter restricts locations of its particles, Low-mass evolution Thought question increasing their uncertainty in momentum Post MS ⊲ But two particles cannot be in same quantum state Broken thermostat Helium fusion (including momentum) at same time Thought question Helium burning ⊲ There must be an effect that limits how much matter can be compressed: degeneracy pressure

Read: Chap 15, 16, S4 10/23/11 – slide 29 How does QM affect stars?

Thermal pressure Announcements HR diagram ⊲ MS explanation Molecules striking the walls of a container (e.g. Review balloon) apply thermal pressure that depends on the Sizes of stars Off the MS temperature inside the balloon Variable stars ⊲ Pulsations Most stars are supported by thermal pressure Cepheids Star clusters Degeneracy pressure Ages of star clusters Testing theory Others? ⊲ Laws of quantum mechanics create a different form QM uncertainty of pressure known as degeneracy pressure ⊲ QM uncertainty Degeneracy in stars ⊲ Squeezing matter restricts locations of its particles, Low-mass evolution Thought question increasing their uncertainty in momentum Post MS ⊲ But two particles cannot be in same quantum state Broken thermostat Helium fusion (including momentum) at same time Thought question Helium burning ⊲ There must be an effect that limits how much matter can be compressed: degeneracy pressure

Read: Chap 15, 16, S4 10/23/11 – slide 29 How does QM affect stars?

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty ⊲ QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 30 Auditorium example

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty ⊲ QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 31 Auditorium example

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty ⊲ QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 31 Degeneracy pressure in stars

Announcements HR diagram Electron degeneracy pressure is what supports white MS explanation dwarfs against gravity Review Sizes of stars Off the MS ⊲ Quantum laws prevent its electrons from being Variable stars Pulsations squeezed into a smaller space Cepheids Star clusters Neutron degeneracy pressure is what supports neutron Ages of star clusters Testing theory stars against gravity Others? QM uncertainty ⊲ Quantum laws prevent its neutrons from being QM uncertainty Degeneracy in squeezed into a smaller space ⊲ stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Thought question Independent of temperature!! Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 32 Life stages of a low-mass star

Star forms On main sequence while hydrogen fuses in the core This is approx. 1010 years for the Sun ages confirm:

⊲ More massive stars exhaust their hydrogen earlier ⊲ Less massive stars exhaust their hydrogen later

Read: Chap 15, 16, S4 10/23/11 – slide 33 Thought question

Announcements What happens when a star can no longer fuse hydrogen to HR diagram MS explanation helium in its core? Review Sizes of stars Off the MS (A) Core cools off Variable stars Pulsations (B) Core shrinks and heats up Cepheids Star clusters Ages of star clusters (C) Core expands and heats up Testing theory Others? (D) Helium fusion immediately begins QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution ⊲ Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 34 Thought question

Announcements What happens when a star can no longer fuse hydrogen to HR diagram MS explanation helium in its core? Review Sizes of stars Off the MS (A) Core cools off Variable stars Pulsations (B) Core shrinks and heats up Cepheids Star clusters Ages of star clusters (C) Core expands and heats up Testing theory Others? (D) Helium fusion immediately begins QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution ⊲ Thought question Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 34 HR diagram track after main sequence

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Observations of star Pulsations clusters show that a Cepheids Star clusters star becomes larger, Ages of star clusters redder, and more Testing theory Others? luminous after its QM uncertainty time on the main QM uncertainty Degeneracy in stars sequence is over Low-mass evolution Thought question ⊲ Post MS Broken thermostat Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 35 Broken thermostat

As the core contracts, H begins fusing to He in a shell around the core Luminosity increases because the core thermostat is broken— the increasing fusion rate in the shell does not stop the core from contracting Helium-core density increases ⇒ pressure becomes degenerate

Read: Chap 15, 16, S4 10/23/11 – slide 36 Helium fusion

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? Helium fusion does not begin right away because it QM uncertainty QM uncertainty requires higher temperatures than hydrogen fusion Degeneracy in stars Low-mass evolution Larger charge leads to greater repulsion Thought question Post MS Fusion of two helium nuclei does not work, so helium Broken thermostat fusion must combine three He nuclei to make ⊲ Helium fusion Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 37 Thought question

Announcements What happens in a low-mass star when core temperature rises HR diagram MS explanation enough for helium fusion to begin? Review Sizes of stars Off the MS (A) Helium fusion slowly starts up Variable stars Pulsations (B) Hydrogen fusion stops Cepheids Star clusters Ages of star clusters (C) Helium fusion rises very sharply Testing theory Others? Hint: Degeneracy pressure is the main form of pressure in the QM uncertainty QM uncertainty inert helium core Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion ⊲ Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 38 Thought question

Announcements What happens in a low-mass star when core temperature rises HR diagram MS explanation enough for helium fusion to begin? Review Sizes of stars Off the MS (A) Helium fusion slowly starts up Variable stars Pulsations (B) Hydrogen fusion stops Cepheids Star clusters Ages of star clusters (C) Helium fusion rises very sharply Testing theory Others? Hint: Degeneracy pressure is the main form of pressure in the QM uncertainty QM uncertainty inert helium core Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion ⊲ Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 38 Helium flash

Announcements HR diagram Thermostat is broken in low-mass red giant because MS explanation degeneracy pressure supports core Review Sizes of stars Off the MS Core temperature rises rapidly when helium fusion Variable stars begins Pulsations Cepheids Helium fusion rate skyrockets until thermal pressure Star clusters Ages of star clusters takes over and expands core again Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion ⊲ Thought question Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 39 Helium burning

Announcements HR diagram MS explanation Review Sizes of stars Off the MS Variable stars Pulsations Cepheids Star clusters Ages of star clusters Testing theory Others? QM uncertainty QM uncertainty Degeneracy in stars Low-mass evolution Thought question Post MS Broken thermostat Helium fusion Helium burning stars neither shrink nor grow because core Thought question thermostat is temporarily fixed. ⊲ Helium burning

Read: Chap 15, 16, S4 10/23/11 – slide 40