Simulations of a Supernova Imposter

Size: px
Start display at page:

Download "Simulations of a Supernova Imposter"

Transcription

1 The Fate of the Most Massive Stars ASP Conference Series, Vol. 332, 2005 Roberta M. Humphreys and Krzysztof Z. Stanek Simulations of a Supernova Imposter David Arnett, Casey Meakin, and Patrick A. Young Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson AZ Abstract. We discuss possible non-supernova eruptions in massive stars like η Carina, using a combination of stellar evolution and radiation hydrodynamics, to ascertain the essential underlying physics of such phenomena. A summary of a combination of numerical hydrodynamical simulations, in one, two, and three dimensions, is used to explore various facets of the problem. We apply insight from multidimensional simulations to both stellar evolution and stellar hydrodynamics in the case of a 120M star of solar abundances. We conclude that such stars should rapidly evolve to the redward of the Humphreys-Davidson limit, where they become vigorously unstable to density clumping and mass ejection, and predict CNO abundance differences in the clumpy and unclumped medium. 1. INTRODUCTION As discussed in a companion paper at this conference (Young 2004), individual eruptions of η Carinae analogues may have kinetic energies of > ergs, within an order of magnitude of a core collapse supernova. In this paper we address the hydrodynamics of the onset of catastrophic eruptions of the most massive stars, the supernova imposters. 2. Physics of Massive Star One of the most massive of well-observed stellar objects is η Carinae. It represents an extreme case for stellar physics. The increasing importance of radiation pressure with increasing stellar mass is well known; it is accompanied by an increase in the importance of radiation energy relative to thermal energy in ions and electrons. This causes the adiabatic exponent for the radiation-gas mixture to approach its marginal stability value of γ = 4/3. It also implies that leakage of thermal energy is enhanced (for the sun only about a percent of the internal energy is in the form of radiation). As Cowling (1941) showed, the normal modes of stars in reaction to a perturbation are p-modes (sonic waves) and g-modes (gravity waves). In the compressible case, we have the Brunt-Väisälä frequency N 2 = gδ H P ( ad + ϕ δ µ), (1) from Kippenhahn & Weiget (1990), eq. 6.18, where the symbols have their usual meaning, or Hansen & Kawaler (1994), eq and Notice than 75

2 76 Arnett, Meakin, and Young Figure 1. Density Perturbations from g-modes. For simplicity a 2D simulation is shown. The vertical dimension represents a fractional variation in density. The bottom part of the wedge is convective. At the transition to the convective stability boundary, density variation reach a maximum, due to the interaction of convective plumes with the elastic nonconvective region. Beyond this boundary density variations carried by internal waves may be seen. This simple idea solves much of the old problem in stellar evolution of what to do at the edge of convective zones. The interface deforms into a nonspherical surface, with mixing only occurring due to higher order processes (173). The importance of such effects increases with solar mass, and should be included in models of η Carina. the quantity in parenthesis is the Ledoux condition for convective instability. When this is negative, the linear solutions grow exponentially, giving rise to convection, and for the low viscosity of stellar plasma, turbulence. While the nonconvective case, in the linear limit, gives a discrete spectrum of wave solutions, the turbulence spectrum is continuous. Convection will drive wave motion in nonconvective region. For stellar convection, the temperature gradient is almost adiabatic, so N 2 gδ H P, (2) resulting in an impedence mismatch. This is less pronounced for the gravity modes (the internal waves in the stratified plasma) because of their lower fre-

3 SN Imposters 77 quencies, so convection drives internal waves. Recent 2D and 3D hydrodynamic simulations have suggested the deep importance of this coupling for stellar evolution (Young et al. 2001, 2004, Young & Arnett 2004), in addition to its diagnostic importance via stellar seismology. Internal waves become more important for larger stellar masses; their effects are subtle for the Sun. The Sun rings like a bell with sound waves. These, in combination with gravity and rotation determine the shape of stars. We concentrate on slowly rotating stars for our exploratation; this is an over-simplification (see Maeder and Meynet, this conference). On a longer time scale for most stars, radiative diffusion (and sometimes convection) transfer energy within the star. The sonic time scale is τ sound l/s, where l is a characteristic dimension of the region considered, and s is the sound speed. The radiative diffusion time scale is tau rad l 2 /λc = l 2 ρκ/c, where λ is the radiative mean free path, ρ the mass density, κ the opacity, and c the speed of light. While c s, this is generally overcome by l λ. For massive stars, the opacity approaches that for Thomson scattering, which is a minimum for ionized stellar plasma. The lowest densities are found in the envelopes of very extended stars, the red supergiants. Thus, for massive red supergiants, the time scale for sound travel can exceed that for the time scale from radiative heat transfer. This is the regime of the strange modes (see Glatzel, this conference). Traditional stellar pulsation is built on the notion of Eddington that τ sound τ rad, which is not true in the outer layers of such stars. This breakdown results in the development of density inversions (density increasing outward) in the envelopes of red giant models, and as we will argue, favors the formation of density inhomogeneities (clumping). 3. Progenitor Evolution and Initial Model The stellar evolutionary sequences were done with the TYCHO code (Young et al 2001, Young & Arnett 2004). Features of the calculations reported here are: The stars have masses of 120M, with solar abundances. A Kudritzki algorithm is used for blue supergiant mass loss (modelling line-driven radiative winds). The hydrostatic evolution is conducted with hydrodynamically consistent convective boundaries (mixing induced by internal waves) as one option (Young et al. 2004, Young & Arnett 2004). We find excellent agreement with observations of lower mass stars (0.4 < M/M < 23 (see Young et al 2001, Young & Arnett 2004, Young 2004). The hydrodynamic evolution is computed in one dimension (spherical symmetry), with identical microphysics physics as used in the evolutionary stages, but with dynamic convection and flux-limited radiative diffusion, The OPAL (Iglesias & Rogers 1996) and Alexander & Ferguson (1994) opacities, the OPAL, Timmes, and Arnett equations of state, and a 176 nucleus nuclear reaction network are used. Rotation is set to zero.

4 78 Arnett, Meakin, and Young Figure 2. Within the uncertainty about mixing, qualitatively different types of evolution are possible. The two tracks shown are identical except for mixing; after core hydrogen exhaustion they move to opposite sides of the HR diagram. The model with internal wave mixing goes to the red side. The most massive, well observed wide eclipsing are shown, as well as some Cepheids, to illustrate how far from standard stellar evolution conditions these models are. Figure 2 shows two trajectories for a 120M star in the HR diagram which differ by the treatment of mixing (both withing the range used in recent calculations). The paths diverge after hydrogen enhaustion, giving different mass loss histories. The model with wave induced mixing trepasses into the Humphreys- Davidson forbidden zone, while less mixing allows the star to return to the blue. Also plotted are data for some wide eclipsing binaries and some Cepheid variables; the 120M star lies far from the well-tested regions of the HR diagram. The red supergiant will be taken to be the initial model for further evolution with numerical hydrodynamics. The structure is shown in Figure 3. About 4M were lost in the blue supergiant stage (core hydrogen burning). Almost all the remaining 116M has been processed in the convective core by CNO burning, so by mass there is only a sliver (about 8M ) left which contains hydrogen. However, the radius of the helium core is < cm, while the photosphere lies at a radius > cm. By volume the star is hydrogen rich, even though the core contains 108M of nearly pure helium!

5 SN Imposters 79 Figure 3. Hydrogen versus mass coordinate, and hydrogen versus logarithm base 10 of the radius. The 108M core occupies almost no volume; the envelope is made of 8M that is hydrogen rich! 4. Hydrodynamic Experiments The characteristics of the hydrodynamic calculations are: The radial hydrodynamics was done on a lagrangian (comoving) grid, with pseudo-viscous smearing ofshocks. The nonradial hydrodynamics (convective mixing of heat) was done by integrating the buoyancy force against a drag term. The drag was chosen to reproduce mixing length theory as used in the hydrostatic evolution. These choices were guided by our multi-dimensional hydrodynamic simulations. Radiation flow was treated using flux-limited diffusion and the same opacities as before. The equation of state was as before, and partial ionization of hydrogen, helium and metals. No significant burning occurred, although our 176 element network was used. While the hydrodynamic treatment is oversimplified, it does allow us to examine some aspects of radial and nonradial flow in the context of a strong radiation field. The evolution of the core gives an increasing luminosity at the base of the hydrogen envelope. Although the increase is small, the hydrogen envelope is within a few percent of its limiting Eddington luminosity. Figure 4 shows the relaxation of the hydrodynamic model which occurs after rezoning in mass to optimize the numerical computation (right panel). We omit the helium core from the computational grid. The model quickly relaxes to a state near the one that the original zoning gave, and then simply remained hydrostatic. In the left panel, the effect of imposing a plausible increase in luminosity at the bottom of the hydrogen layer. We find that a small outburst results, which is shown in Figure 5. Without the increasing luminosity, this does not happen. It appears that a variety of

6 80 Arnett, Meakin, and Young Figure 4. Left panel: A slowly increasing luminosity is imposed at the base of the envelope. Right panel: Numerical transients quickly relax (in less that a day) to a state similar to the initial hydrostatic one and remain static for centuries of star time. Figure 5. Left panel: The onset of a small outburst, showing surface luminosity versus time. Right panel: Fine structure of the outburst shown on an expanded scale. The width of the pulse is about one day. modes happen to combine to give the outburst. The real situation will be more complex because we allow only radial modes. Is this the great outburst of η Car? Probably not; it is too small. However, it could be an example of what triggers a large outburst (Young 2004). Such nonlinear mixing of modes may be an inportant feature of massive red supergiants. Figure 6 shows snapshots of density and temperature as the envelope lifts off the helium core, which is indicated by the steep rise in both temperature and density at small radius. The density inversion at the outer edge of the envelope maintains its shape as a subsonic expansion occurs. The temperature maintains its photpspheric structure as well. At late time the region around the coreenvelope interface is poorly resolved; this is a worry, as this region may be important for driving by super-eddington radiative acceleration (Young 2004), as well as strange mode effects (see Glatzel, this conference).

7 SN Imposters 81 Figure 6. Left panel: Density versus log radius snapshots. The initial model shows the pronounced density inversion commonly found in models of giant stars. Right panel: Temperature versus log radius snapshots. The helium core lies inside the steep increase at small radius. Figure 7. Left panel: Pressure versus log radius snapshots. Right panel: Fluid velocity versus log radius snapshots. The flows are subsonic. Figure 7 shows snapshots of the pressure profile (left panel) which slowly changes its shape as the envelope lifts off, characteristic of subsonic flow. This is also indicated by the radial velocity snapshots seen in the right panel. However, the picture is more interesting if we examine the convective flow velocities, shown in Figure 8. The velocity scale is a factor of ten larger than in the left panel of Figure 7 for the radial velocities, and are supersonic. Our separation of radial and nonradial flows was predicated on the nonradial flows being a perturbation on the radial; this is not so. The system has pronounced nonradial flow at a epoch at which the thermal relaxation is faster than sonic effects. This is a certain recipe for clumping. Converging flows, from collisions of nonradial waves, will give compression, but efficient radiative flow will resist pressure increase. Similarly, shocks will radiate efficiently. Note that this occurs while still in the opaque limit, so that radiative diffusion is adequate. The convective velocities are higher inward, suggesting the onset of a stellar wind, which will poke through the lower density regions in the inhomogeneous shell. This is suggestive of a multiphase medium, with a higher entropy, faster,

8 82 Arnett, Meakin, and Young Figure 8. wind?). Convective velocity versus log radius snapshots (transition to lower density wind in one phase, and a slower, wind of dense clumps in another. Figure 9 shows the abundance structure. The outer shell is less process by CNO burning, but will clump and be overtaken by the N 14 enriched underlying material. The whole 8M envelope escapes in this simulation, leaving the 108M helium core, which is compact, and highly unstable to the epsilon mechanism (nuclear energized radial pulsations by core helium burning). We recall that 4M were shed by the star in its blue phase; this matter was still less processed by CNO burning. 5. Implications While these calculations suffer from two serious flaws, namely a lack of coupling between radial and nonradial flows and a developing lack of resolution at the core-envelope interface, they provide some clues for proceding to the next step and some robust implications. A significant amount of mass is lost, and there are abundance diagnostics from CNO burning.

9 SN Imposters 83 Figure 9. Detailed abundances versus log radius in the envelope. The outermost matter is most unstable to clumping, and has a different composition: less nitrogen production. Abundance differences are expected between the regions of strongest clumping and those of fastest expansion. There is a strong clumping instability, so radiation spikes are expected. Most of the action occurs in a full 3D hydrodynamics plus radiation diffusion regime. While stellar wind methods will be useful for diagnostics, the driving physics occurs in a non-steady state regime with optical depths greater than unity. The outburst is a hydrodynamic stellar interiors problem, which transitions later to a wind phase. Rotational geometry and a binary companion will have effects which modify the picture, perhaps in important ways. There is no SN imposter yet! However we do get an indication of outburst behavior, and the lack of resolution at the core-envelope interface may weaken this effect (Young (2004) and Glatzel, this conference). What will the He star do? While η Carina has not yet reached this phase, it seems likely to be dramatic, with the unveiling of a very hot and luminous

10 84 Arnett, Meakin, and Young helium star, unstable to nuclearly driven pulsations, within a fairly massive (12M ) nebula. This work was supported in part by a DOE grant to the University of Arizona, and a subcontract to the ASCI Flash Center at the University of Chicago. References Alexander, D. R. & Ferguson, J. W. 1994, ApJ,, 437, 879 Cowling, T. G., 1941, MNRAS, 101, 367 Hansen, C. J., & Kawaler, S. D., 1994, Stellar Interiors, Springer-Verlag Iglesias, C. & Rogers, F. J. 1996, ApJ,, 464, 943 Kippenhahn, R. & Weigert, A. 1990, Stellar Structure and Evolution, Springer-Verlag This conference. Young, P. A. and Arnett, D. 2004, ApJ,, accepted for publication Young, P. A., Knierman, K. A., Rigby, J. R., and Arnett, D., 2003, ApJ,, 595, 1114 Young, P. A., Mamajek, E. E., Arnett, D., & Liebert, J. 2001, ApJ,, 556, 230 Discussion Guzik: What is the temperature of the base of the envelope you re working with? Approximately? 1 Billion degrees? Arnett:It s in an interesting region and I don t really remember. It s of order Maeder: At the beginning of your talk, you mentioned the gravity waves that you consider in the model. Could you comment a bit on the contribution of these gravitiy waves to the transport of chemical elements and to the transport of angular momentum is it significant or not? Arnett: I think we probably agree with you about the transport of angular momentum. Patrick and I wrote a paper where we looked at the lithium and beryllium depletion and we found that with the combination of what we were doing and what Tolonge (?) and Charbonell (?) were doing, we could get a complete picture. But it was important that the rotation both aided and inhibited convection and so we re in agreement there. I think that what happens with the gravity waves is even in the absence of rotation they enhance the mixing, particularily in semi-convection regions, because what s happening, is that you have this marginally stable part of the star which has a H gradient and you re pushing it at the bottom. The more massive the star, the less resistance to mixing it has, because the radiation pressure is going up and when you get to the big guys the effect is more important. Conversely, if we go to low mass stars then this prescription makes almost no difference. Patrick will talk about it later. Davidson: One of the many things we can see in η and can t see in other objects for just practical reasons is the existence of a lot of absurdly slow material. Speeds of 50 km s 1 which is not a natural velocity scale that I can think of in

11 SN Imposters 85 the the object. I don t know whether this is pertinent to your comment about slow ejected stuff but it might be. Arnett: That s what I m thinking. I m pretty sure that there is a dichotomy in the flow velocity, against low speeds and vice versa. What I don t know is what the number is. On the other hand, there is Ishibashi s little homonculus. It isn t quite that slow but it s pretty slow, 200 km s 1 or something like that? And that is also fairly slow. Most of what we ve discussed observationally today is material outside where this is going on. Townsend: Two questions. First, I might have missed the crucial part of your talk but, I m wondering are your simulations 1D, 2D, 3D? Arnett: All the above. What I m doing is piecing together stuff. So, we ve done 2 and 3 D and we have short parts of the stellar evolution cycle, analyzed that, determine that the gravity waves were a dominant mechanism for additional transport of mass and angular momentum. We put that back in the 1D code, evolved it and lo-and-behold it goes over to the rim. Very quickly. Then we look at that and say, well you know it s above 95% of the Eddington limit and what happens if we just let it go? If we let it go and we don t change the luminosity, it just sits there. We let it go and we raise the luminosity, this is what you get. In 1 D. And then I speculate on what I guess would happen in 2 D. Townsend: You already answered my second question which was on whether gravity waves play an important part for transport of angular momentum. You said yes. Is this from your hydro simulations in the 80 s? Arnett: No this is from our hydro simulations. What we re doing is still angular momentum. When we do it without rotation we still have angular momentum in the radial plane so, we re right down to the same equations.

10/17/2012. Stellar Evolution. Lecture 14. NGC 7635: The Bubble Nebula (APOD) Prelim Results. Mean = 75.7 Stdev = 14.7

10/17/2012. Stellar Evolution. Lecture 14. NGC 7635: The Bubble Nebula (APOD) Prelim Results. Mean = 75.7 Stdev = 14.7 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 10/17/2012 Stellar Evolution Lecture 14 NGC 7635: The Bubble Nebula (APOD) Prelim Results 9 8 7 6 5 4 3 2 1 0 Mean = 75.7 Stdev = 14.7 1 Energy

More information

Astro 1050 Fri. Apr. 10, 2015

Astro 1050 Fri. Apr. 10, 2015 Astro 1050 Fri. Apr. 10, 2015 Today: Continue Ch. 13: Star Stuff Reading in Bennett: For Monday: Finish Chapter 13 Star Stuff Reminders: Ch. 12 HW now on Mastering Astronomy, due Monday. Ch. 13 will be

More information

VII. Hydrodynamic theory of stellar winds

VII. Hydrodynamic theory of stellar winds VII. Hydrodynamic theory of stellar winds observations winds exist everywhere in the HRD hydrodynamic theory needed to describe stellar atmospheres with winds Unified Model Atmospheres: - based on the

More information

Chapter 12 Stellar Evolution

Chapter 12 Stellar Evolution Chapter 12 Stellar Evolution Guidepost Stars form from the interstellar medium and reach stability fusing hydrogen in their cores. This chapter is about the long, stable middle age of stars on the main

More information

HR Diagram, Star Clusters, and Stellar Evolution

HR Diagram, Star Clusters, and Stellar Evolution Ay 1 Lecture 9 M7 ESO HR Diagram, Star Clusters, and Stellar Evolution 9.1 The HR Diagram Stellar Spectral Types Temperature L T Y The Hertzsprung-Russel (HR) Diagram It is a plot of stellar luminosity

More information

Progress in Multi-Dimensional Stellar Evolution

Progress in Multi-Dimensional Stellar Evolution Progress in Multi-Dimensional Stellar Evolution Casey A. Meakin Steward Observatory University of Arizona July 2006 David Arnett (Arizona), Patrick Young (Arizona/LANL) Outline Astronomical Perspective

More information

Chapter 17 Lecture. The Cosmic Perspective Seventh Edition. Star Stuff Pearson Education, Inc.

Chapter 17 Lecture. The Cosmic Perspective Seventh Edition. Star Stuff Pearson Education, Inc. Chapter 17 Lecture The Cosmic Perspective Seventh Edition Star Stuff Star Stuff 17.1 Lives in the Balance Our goals for learning: How does a star's mass affect nuclear fusion? How does a star's mass affect

More information

1. What is the primary difference between the evolution of a low-mass star and that of a high-mass star?

1. What is the primary difference between the evolution of a low-mass star and that of a high-mass star? FYI: The Lives of Stars E3:R6b 1. Read FYI: The Lives of Stars As you read use the spaces below to write down any information you find especially interesting. Also define the bold terms used in the text.

More information

The effect of turbulent pressure on the red giants and AGB stars

The effect of turbulent pressure on the red giants and AGB stars Astron. Astrophys. 317, 114 120 (1997) ASTRONOMY AND ASTROHYSICS The effect of turbulent pressure on the red giants AGB stars I. On the internal structure evolution S.Y. Jiang R.Q. Huang Yunnan observatory,

More information

Week 8: Stellar winds So far, we have been discussing stars as though they have constant masses throughout their lifetimes. On the other hand, toward

Week 8: Stellar winds So far, we have been discussing stars as though they have constant masses throughout their lifetimes. On the other hand, toward Week 8: Stellar winds So far, we have been discussing stars as though they have constant masses throughout their lifetimes. On the other hand, toward the end of the discussion of what happens for post-main

More information

Stars and their properties: (Chapters 11 and 12)

Stars and their properties: (Chapters 11 and 12) Stars and their properties: (Chapters 11 and 12) To classify stars we determine the following properties for stars: 1. Distance : Needed to determine how much energy stars produce and radiate away by using

More information

Before proceeding to Chapter 20 More on Cluster H-R diagrams: The key to the chronology of our Galaxy Below are two important HR diagrams:

Before proceeding to Chapter 20 More on Cluster H-R diagrams: The key to the chronology of our Galaxy Below are two important HR diagrams: Before proceeding to Chapter 20 More on Cluster H-R diagrams: The key to the chronology of our Galaxy Below are two important HR diagrams: 1. The evolution of a number of stars all formed at the same time

More information

9.1 Introduction. 9.2 Static Models STELLAR MODELS

9.1 Introduction. 9.2 Static Models STELLAR MODELS M. Pettini: Structure and Evolution of Stars Lecture 9 STELLAR MODELS 9.1 Introduction Stars are complex physical systems, but not too complex to be modelled numerically and, with some simplifying assumptions,

More information

Life and Death of a Star. Chapters 20 and 21

Life and Death of a Star. Chapters 20 and 21 Life and Death of a Star Chapters 20 and 21 90 % of a stars life Most stars spend most of their lives on the main sequence. A star like the Sun, for example, after spending a few tens of millions of years

More information

UNIVERSITY OF SOUTHAMPTON

UNIVERSITY OF SOUTHAMPTON UNIVERSITY OF SOUTHAMPTON PHYS3010W1 SEMESTER 2 EXAMINATION 2014-2015 STELLAR EVOLUTION: MODEL ANSWERS Duration: 120 MINS (2 hours) This paper contains 8 questions. Answer all questions in Section A and

More information

Evolution Beyond the Red Giants

Evolution Beyond the Red Giants Evolution Beyond the Red Giants Interior Changes Sub-giant star 1 Post-Helium Burning What happens when there is a new core of non-burning C and O? 1. The core must contract, which increases the pressure

More information

The Later Evolution of Low Mass Stars (< 8 solar masses)

The Later Evolution of Low Mass Stars (< 8 solar masses) The Later Evolution of Low Mass Stars (< 8 solar masses) http://apod.nasa.gov/apod/astropix.html The sun - past and future central density also rises though average density decreases During 10 billion

More information

Ay 1 Lecture 8. Stellar Structure and the Sun

Ay 1 Lecture 8. Stellar Structure and the Sun Ay 1 Lecture 8 Stellar Structure and the Sun 8.1 Stellar Structure Basics How Stars Work Hydrostatic Equilibrium: gas and radiation pressure balance the gravity Thermal Equilibrium: Energy generated =

More information

Chapter 12 Review. 2) About 90% of the star's total life is spent on the main sequence. 2)

Chapter 12 Review. 2) About 90% of the star's total life is spent on the main sequence. 2) Chapter 12 Review TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false. 1) As a main-sequence star, the Sun's hydrogen supply should last about 10 billion years from the zero-age

More information

7. The Evolution of Stars a schematic picture (Heavily inspired on Chapter 7 of Prialnik)

7. The Evolution of Stars a schematic picture (Heavily inspired on Chapter 7 of Prialnik) 7. The Evolution of Stars a schematic picture (Heavily inspired on Chapter 7 of Prialnik) In the previous chapters we have seen that the timescale of stellar evolution is set by the (slow) rate of consumption

More information

Lecture 8: Stellar evolution II: Massive stars

Lecture 8: Stellar evolution II: Massive stars Lecture 8: Stellar evolution II: Massive stars Senior Astrophysics 2018-03-27 Senior Astrophysics Lecture 8: Stellar evolution II: Massive stars 2018-03-27 1 / 29 Outline 1 Stellar models 2 Convection

More information

Stellar Winds: Mechanisms and Dynamics

Stellar Winds: Mechanisms and Dynamics Astrofysikalisk dynamik, VT 010 Stellar Winds: Mechanisms and Dynamics Lecture Notes Susanne Höfner Department of Physics and Astronomy Uppsala University 1 Most stars have a stellar wind, i.e. and outflow

More information

ASTR-1020: Astronomy II Course Lecture Notes Section VI

ASTR-1020: Astronomy II Course Lecture Notes Section VI ASTR-1020: Astronomy II Course Lecture Notes Section VI Dr. Donald G. Luttermoser East Tennessee State University Edition 4.0 Abstract These class notes are designed for use of the instructor and students

More information

Astronomy. Stellar Evolution

Astronomy. Stellar Evolution Astronomy A. Dayle Hancock adhancock@wm.edu Small 239 Office hours: MTWR 10-11am Stellar Evolution Main Sequence star changes during nuclear fusion What happens when the fuel runs out Old stars and second

More information

Heading for death. q q

Heading for death. q q Hubble Photos Credit: NASA, The Hubble Heritage Team (STScI/AURA) Heading for death. q q q q q q Leaving the main sequence End of the Sunlike star The helium core The Red-Giant Branch Helium Fusion Helium

More information

AST1100 Lecture Notes

AST1100 Lecture Notes AST1100 Lecture Notes 20: Stellar evolution: The giant stage 1 Energy transport in stars and the life time on the main sequence How long does the star remain on the main sequence? It will depend on the

More information

Phys 100 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 9

Phys 100 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 9 Phys 0 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 9 MULTIPLE CHOICE 1. We know that giant stars are larger in diameter than the sun because * a. they are more luminous but have about the

More information

Energy transport: convection

Energy transport: convection Outline Introduction: Modern astronomy and the power of quantitative spectroscopy Basic assumptions for classic stellar atmospheres: geometry, hydrostatic equilibrium, conservation of momentum-mass-energy,

More information

Review: HR Diagram. Label A, B, C respectively

Review: HR Diagram. Label A, B, C respectively Stellar Evolution Review: HR Diagram Label A, B, C respectively A C B a) A: White dwarfs, B: Giants, C: Main sequence b) A: Main sequence, B: Giants, C: White dwarfs c) A: Main sequence, B: White Dwarfs,

More information

Tidal effects and periastron events in binary stars

Tidal effects and periastron events in binary stars Tidal effects and periastron events in binary stars Gloria Koenigsberger & Edmundo Moreno Universidad Nacional Autónoma de México gloria@fis.unam.mx; edmundo@astroscu.unam.mx December 8, 2008 ABSTRACT

More information

dp dr = GM c = κl 4πcr 2

dp dr = GM c = κl 4πcr 2 RED GIANTS There is a large variety of stellar models which have a distinct core envelope structure. While any main sequence star, or any white dwarf, may be well approximated with a single polytropic

More information

Chapter 19: The Evolution of Stars

Chapter 19: The Evolution of Stars Chapter 19: The Evolution of Stars Why do stars evolve? (change from one state to another) Energy Generation fusion requires fuel, fuel is depleted [fig 19.2] at higher temperatures, other nuclear process

More information

Evolution from the Main-Sequence

Evolution from the Main-Sequence 9 Evolution from the Main-Sequence Lecture 9 Evolution from the Main-Sequence P. Hily-Blant (Master PFN) Stellar structure and evolution 2016-17 111 / 159 9 Evolution from the Main-Sequence 1. Overview

More information

Lecture 16: The life of a low-mass star. Astronomy 111 Monday October 23, 2017

Lecture 16: The life of a low-mass star. Astronomy 111 Monday October 23, 2017 Lecture 16: The life of a low-mass star Astronomy 111 Monday October 23, 2017 Reminders Online homework #8 due Monday at 3pm Exam #2: Monday, 6 November 2017 The Main Sequence ASTR111 Lecture 16 Main sequence

More information

High Mass Stars. Dr Ken Rice. Discovering Astronomy G

High Mass Stars. Dr Ken Rice. Discovering Astronomy G High Mass Stars Dr Ken Rice High mass star formation High mass star formation is controversial! May form in the same way as low-mass stars Gravitational collapse in molecular clouds. May form via competitive

More information

Topics for Today s Class

Topics for Today s Class Foundations of Astronomy 13e Seeds Chapter 11 Formation of Stars and Structure of Stars Topics for Today s Class 1. Making Stars from the Interstellar Medium 2. Evidence of Star Formation: The Orion Nebula

More information

Stellar Evolution Stars spend most of their lives on the main sequence. Evidence: 90% of observable stars are main-sequence stars.

Stellar Evolution Stars spend most of their lives on the main sequence. Evidence: 90% of observable stars are main-sequence stars. Stellar Evolution Stars spend most of their lives on the main sequence. Evidence: 90% of observable stars are main-sequence stars. Stellar evolution during the main-sequence life-time, and during the post-main-sequence

More information

10/26/ Star Birth. Chapter 13: Star Stuff. How do stars form? Star-Forming Clouds. Mass of a Star-Forming Cloud. Gravity Versus Pressure

10/26/ Star Birth. Chapter 13: Star Stuff. How do stars form? Star-Forming Clouds. Mass of a Star-Forming Cloud. Gravity Versus Pressure 10/26/16 Lecture Outline 13.1 Star Birth Chapter 13: Star Stuff How do stars form? Our goals for learning: How do stars form? How massive are newborn stars? Star-Forming Clouds Stars form in dark clouds

More information

Introduction. Stellar Objects: Introduction 1. Why should we care about star astrophysics?

Introduction. Stellar Objects: Introduction 1. Why should we care about star astrophysics? Stellar Objects: Introduction 1 Introduction Why should we care about star astrophysics? stars are a major constituent of the visible universe understanding how stars work is probably the earliest major

More information

Chapter 17: Stellar Evolution

Chapter 17: Stellar Evolution Astr 2310 Thurs. Mar. 30, 2017 Today s Topics Chapter 17: Stellar Evolution Birth of Stars and Pre Main Sequence Evolution Evolution on and off the Main Sequence Solar Mass Stars Massive Stars Low Mass

More information

Chapter 11 The Formation and Structure of Stars

Chapter 11 The Formation and Structure of Stars Chapter 11 The Formation and Structure of Stars Guidepost The last chapter introduced you to the gas and dust between the stars that are raw material for new stars. Here you will begin putting together

More information

Astronomy 104: Stellar Astronomy

Astronomy 104: Stellar Astronomy Astronomy 104: Stellar Astronomy Lecture 18: A High-Mass Star s Life and Death (a.k.a. - Things that go BOOM in the night) Spring Semester 2013 Dr. Matt Craig 1 1 Reading Today: Chapter 12.1 (Life and

More information

Low mass stars. Sequence Star Giant. Red. Planetary Nebula. White Dwarf. Interstellar Cloud. White Dwarf. Interstellar Cloud. Planetary Nebula.

Low mass stars. Sequence Star Giant. Red. Planetary Nebula. White Dwarf. Interstellar Cloud. White Dwarf. Interstellar Cloud. Planetary Nebula. Low mass stars Interstellar Cloud Main Sequence Star Red Giant Planetary Nebula White Dwarf Interstellar Cloud Main Sequence Star Red Giant Planetary Nebula White Dwarf Low mass stars Interstellar Cloud

More information

The physics of stars. A star begins simply as a roughly spherical ball of (mostly) hydrogen gas, responding only to gravity and it s own pressure.

The physics of stars. A star begins simply as a roughly spherical ball of (mostly) hydrogen gas, responding only to gravity and it s own pressure. Lecture 4 Stars The physics of stars A star begins simply as a roughly spherical ball of (mostly) hydrogen gas, responding only to gravity and it s own pressure. X-ray ultraviolet infrared radio To understand

More information

Astronomy 210. Outline. Stellar Properties. The Mosquito Dilemma. Solar Observing & HW9 due April 15 th Stardial 2 is available.

Astronomy 210. Outline. Stellar Properties. The Mosquito Dilemma. Solar Observing & HW9 due April 15 th Stardial 2 is available. Astronomy 210 Outline This Class (Lecture 31): Stars: Spectra and the H-R Diagram Next Class: Life and Death of the Sun Solar Observing & HW9 due April 15 th Stardial 2 is available. The Mosquito dilemma

More information

Chapter 12 Stellar Evolution

Chapter 12 Stellar Evolution Chapter 12 Stellar Evolution Guidepost This chapter is the heart of any discussion of astronomy. Previous chapters showed how astronomers make observations with telescopes and how they analyze their observations

More information

Stellar Astronomy Sample Questions for Exam 4

Stellar Astronomy Sample Questions for Exam 4 Stellar Astronomy Sample Questions for Exam 4 Chapter 15 1. Emission nebulas emit light because a) they absorb high energy radiation (mostly UV) from nearby bright hot stars and re-emit it in visible wavelengths.

More information

Guiding Questions. Stellar Evolution. Stars Evolve. Interstellar Medium and Nebulae

Guiding Questions. Stellar Evolution. Stars Evolve. Interstellar Medium and Nebulae Guiding Questions Stellar Evolution 1. Why do astronomers think that stars evolve? 2. What kind of matter exists in the spaces between the stars? 3. What steps are involved in forming a star like the Sun?

More information

Pre Main-Sequence Evolution

Pre Main-Sequence Evolution Stellar Astrophysics: Stellar Evolution Pre Main-Sequence Evolution The free-fall time scale is describing the collapse of the (spherical) cloud to a protostar 1/2 3 π t ff = 32 G ρ With the formation

More information

The life of a low-mass star. Astronomy 111

The life of a low-mass star. Astronomy 111 Lecture 16: The life of a low-mass star Astronomy 111 Main sequence membership For a star to be located on the Main Sequence in the H-R diagram: must fuse Hydrogen into Helium in its core. must be in a

More information

Life of a High-Mass Stars

Life of a High-Mass Stars Life of a High-Mass Stars 1 Evolutionary Tracks Paths of high-mass stars on the HR Diagram are different from those of low-mass stars. Once these stars leave the main sequence, they quickly grow in size

More information

Astronomy Ch. 20 Stellar Evolution. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Astronomy Ch. 20 Stellar Evolution. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Name: Period: Date: Astronomy Ch. 20 Stellar Evolution MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A star (no matter what its mass) spends

More information

Astronomy Ch. 20 Stellar Evolution. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Astronomy Ch. 20 Stellar Evolution. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Name: Period: Date: Astronomy Ch. 20 Stellar Evolution MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A star (no matter what its mass) spends

More information

4 Oscillations of stars: asteroseismology

4 Oscillations of stars: asteroseismology 4 Oscillations of stars: asteroseismology The HR diagram below shows a whole variety of different classes of variable or pulsating/oscillating stars. The study of these various classes constitutes the

More information

11/19/08. Gravitational equilibrium: The outward push of pressure balances the inward pull of gravity. Weight of upper layers compresses lower layers

11/19/08. Gravitational equilibrium: The outward push of pressure balances the inward pull of gravity. Weight of upper layers compresses lower layers Gravitational equilibrium: The outward push of pressure balances the inward pull of gravity Weight of upper layers compresses lower layers Gravitational equilibrium: Energy provided by fusion maintains

More information

THE 82ND ARTHUR H. COMPTON LECTURE SERIES

THE 82ND ARTHUR H. COMPTON LECTURE SERIES THE 82ND ARTHUR H. COMPTON LECTURE SERIES by Dr. Manos Chatzopoulos Enrico Fermi Postdoctoral Fellow FLASH Center for Computational Science Department of Astronomy & Astrophysics University of Chicago

More information

Compton Lecture #4: Massive Stars and. Supernovae. Welcome! On the back table:

Compton Lecture #4: Massive Stars and. Supernovae. Welcome! On the back table: Compton Lecture #4: Massive Stars and Welcome! On the back table: Supernovae Lecture notes for today s s lecture Extra copies of last week s s are on the back table Sign-up sheets please fill one out only

More information

THIRD-YEAR ASTROPHYSICS

THIRD-YEAR ASTROPHYSICS THIRD-YEAR ASTROPHYSICS Problem Set: Stellar Structure and Evolution (Dr Ph Podsiadlowski, Michaelmas Term 2006) 1 Measuring Stellar Parameters Sirius is a visual binary with a period of 4994 yr Its measured

More information

Stellar Evolution. Eta Carinae

Stellar Evolution. Eta Carinae Stellar Evolution Eta Carinae Evolution of Main Sequence Stars solar mass star: from: Markus Bottcher lecture notes, Ohio University Evolution off the Main Sequence: Expansion into a Red Giant Inner core

More information

Why Do Stars Leave the Main Sequence? Running out of fuel

Why Do Stars Leave the Main Sequence? Running out of fuel Star Deaths Why Do Stars Leave the Main Sequence? Running out of fuel Observing Stellar Evolution by studying Globular Cluster HR diagrams Plot stars in globular clusters in Hertzsprung-Russell diagram

More information

18. Stellar Birth. Initiation of Star Formation. The Orion Nebula: A Close-Up View. Interstellar Gas & Dust in Our Galaxy

18. Stellar Birth. Initiation of Star Formation. The Orion Nebula: A Close-Up View. Interstellar Gas & Dust in Our Galaxy 18. Stellar Birth Star observations & theories aid understanding Interstellar gas & dust in our galaxy Protostars form in cold, dark nebulae Protostars evolve into main-sequence stars Protostars both gain

More information

Exam 2. Topics for Today s Class 4/16/2018. Announcements for Labs. Chapter 12. Stellar Evolution. Guidepost

Exam 2. Topics for Today s Class 4/16/2018. Announcements for Labs. Chapter 12. Stellar Evolution. Guidepost Announcements for Labs. Phys1403 Stars and Galaxies Instructor: Dr. Goderya Lab 6 Measuring magnitude of stars as a function of time, now Due on Monday April 23 rd During class time Lab 13 Last Lab of

More information

Fundamental Stellar Parameters. Radiative Transfer. Stellar Atmospheres

Fundamental Stellar Parameters. Radiative Transfer. Stellar Atmospheres Fundamental Stellar Parameters Radiative Transfer Stellar Atmospheres Equations of Stellar Structure Basic Principles Equations of Hydrostatic Equilibrium and Mass Conservation Central Pressure, Virial

More information

The Life Cycles of Stars. Modified from Information provided by: Dr. Jim Lochner, NASA/GSFC

The Life Cycles of Stars. Modified from Information provided by: Dr. Jim Lochner, NASA/GSFC The Life Cycles of Stars Modified from Information provided by: Dr. Jim Lochner, NASA/GSFC Twinkle, Twinkle, Little Star... What do you see? How I Wonder What You Are... Stars have: Different Colors -

More information

Today The Sun. Events

Today The Sun. Events Today The Sun Events Last class! Homework due now - will count best 5 of 6 Final exam Dec. 20 @ 12:00 noon here Review this Course! www.case.edu/utech/course-evaluations/ The Sun the main show in the solar

More information

Chapters 12 and 13 Review: The Life Cycle and Death of Stars. How are stars born, and how do they die? 4/1/2009 Habbal Astro Lecture 27 1

Chapters 12 and 13 Review: The Life Cycle and Death of Stars. How are stars born, and how do they die? 4/1/2009 Habbal Astro Lecture 27 1 Chapters 12 and 13 Review: The Life Cycle and Death of Stars How are stars born, and how do they die? 4/1/2009 Habbal Astro 110-01 Lecture 27 1 Stars are born in molecular clouds Clouds are very cold:

More information

Introductory Astrophysics A113. Death of Stars. Relation between the mass of a star and its death White dwarfs and supernovae Enrichment of the ISM

Introductory Astrophysics A113. Death of Stars. Relation between the mass of a star and its death White dwarfs and supernovae Enrichment of the ISM Goals: Death of Stars Relation between the mass of a star and its death White dwarfs and supernovae Enrichment of the ISM Low Mass Stars (M

More information

Stellar Explosions (ch. 21)

Stellar Explosions (ch. 21) Stellar Explosions (ch. 21) First, a review of low-mass stellar evolution by means of an illustration I showed in class. You should be able to talk your way through this diagram and it should take at least

More information

Outline - March 18, H-R Diagram Review. Protostar to Main Sequence Star. Midterm Exam #2 Tuesday, March 23

Outline - March 18, H-R Diagram Review. Protostar to Main Sequence Star. Midterm Exam #2 Tuesday, March 23 Midterm Exam #2 Tuesday, March 23 Outline - March 18, 2010 Closed book Will cover Lecture 8 (Special Relativity) through Lecture 14 (Star Formation) only If a topic is in the book, but was not covered

More information

A Star Becomes a Star

A Star Becomes a Star A Star Becomes a Star October 28, 2002 1) Stellar lifetime 2) Red Giant 3) White Dwarf 4) Supernova 5) More massive stars Review Solar winds/sunspots Gases and Dust Molecular clouds Protostars/Birth of

More information

Stellar Interiors - Hydrostatic Equilibrium and Ignition on the Main Sequence.

Stellar Interiors - Hydrostatic Equilibrium and Ignition on the Main Sequence. Stellar Interiors - Hydrostatic Equilibrium and Ignition on the Main Sequence http://apod.nasa.gov/apod/astropix.html Outline of today s lecture Hydrostatic equilibrium: balancing gravity and pressure

More information

Low-mass Stellar Evolution

Low-mass Stellar Evolution Low-mass Stellar Evolution The lives of low-mass stars And the lives of massive stars The Structure of the Sun Let s review: The Sun is held together by? The inward force is balanced by? Thinking about

More information

Astro 1050 Wed. Apr. 5, 2017

Astro 1050 Wed. Apr. 5, 2017 Astro 1050 Wed. Apr. 5, 2017 Today: Ch. 17, Star Stuff Reading in Horizons: For Mon.: Finish Ch. 17 Star Stuff Reminders: Rooftop Nighttime Observing Mon, Tues, Wed. 1 Ch.9: Interstellar Medium Since stars

More information

Numerical simulations of fluid models in astrophysics From stellar jets to CO white dwarfs

Numerical simulations of fluid models in astrophysics From stellar jets to CO white dwarfs Numerical simulations of fluid models in astrophysics From stellar jets to CO white dwarfs (or, how things sometimes work pretty well and sometimes do not) Francesco Rubini Dipartimento di Astronomia,

More information

Overview spherical accretion

Overview spherical accretion Spherical accretion - AGN generates energy by accretion, i.e., capture of ambient matter in gravitational potential of black hole -Potential energy can be released as radiation, and (some of) this can

More information

TA feedback forms are online!

TA feedback forms are online! 1 Announcements TA feedback forms are online! find the link at the class website. Please take 5 minutes to tell your TAs your opinion. In case you did not notice, the Final is set for 03/21 from 12:00-3:00

More information

Recall what you know about the Big Bang.

Recall what you know about the Big Bang. What is this? Recall what you know about the Big Bang. Most of the normal matter in the universe is made of what elements? Where do we find most of this normal matter? Interstellar medium (ISM) The universe

More information

The Evolution of Low Mass Stars

The Evolution of Low Mass Stars The Evolution of Low Mass Stars Key Ideas: Low Mass = M < 4 M sun Stages of Evolution of a Low Mass star: Main Sequence star star star Asymptotic Giant Branch star Planetary Nebula phase White Dwarf star

More information

Convection When the radial flux of energy is carried by radiation, we derived an expression for the temperature gradient: dt dr = - 3

Convection When the radial flux of energy is carried by radiation, we derived an expression for the temperature gradient: dt dr = - 3 Convection When the radial flux of energy is carried by radiation, we derived an expression for the temperature gradient: dt dr = - 3 4ac kr L T 3 4pr 2 Large luminosity and / or a large opacity k implies

More information

Birth & Death of Stars

Birth & Death of Stars Birth & Death of Stars Objectives How are stars formed How do they die How do we measure this The Interstellar Medium (ISM) Vast clouds of gas & dust lie between stars Diffuse hydrogen clouds: dozens of

More information

Astronomy 1 Fall Reminder: When/where does your observing session meet? [See from your TA.]

Astronomy 1 Fall Reminder: When/where does your observing session meet? [See  from your TA.] Astronomy 1 Fall 2016 Reminder: When/where does your observing session meet? [See email from your TA.] Lecture 9, October 25, 2016 Previously on Astro-1 What is the Moon made of? How did the Moon form?

More information

Accretion Mechanisms

Accretion Mechanisms Massive Protostars Accretion Mechanism Debate Protostellar Evolution: - Radiative stability - Deuterium shell burning - Contraction and Hydrogen Ignition Stahler & Palla (2004): Section 11.4 Accretion

More information

Properties of Stars. Characteristics of Stars

Properties of Stars. Characteristics of Stars Properties of Stars Characteristics of Stars A constellation is an apparent group of stars originally named for mythical characters. The sky contains 88 constellations. Star Color and Temperature Color

More information

Spiral Density waves initiate star formation

Spiral Density waves initiate star formation Spiral Density waves initiate star formation A molecular cloud passing through the Sagittarius spiral arm Spiral arm Gas outflows from super supernova or O/B star winds Initiation of star formation Supernova

More information

Stellar Structure and Evolution

Stellar Structure and Evolution Stellar Structure and Evolution Achim Weiss Max-Planck-Institut für Astrophysik 01/2014 Stellar Structure p.1 Stellar evolution overview 01/2014 Stellar Structure p.2 Mass ranges Evolution of stars with

More information

Astronomy II (ASTR1020) Exam 3 Test No. 3D

Astronomy II (ASTR1020) Exam 3 Test No. 3D Astronomy II (ASTR1020) Exam 3 Test No. 3D 23 October 2001 The answers of this multiple choice exam are to be indicated on the Scantron with a No. 2 pencil. Don t forget to write your name and the Test

More information

Stars IV Stellar Evolution

Stars IV Stellar Evolution Stars IV Stellar Evolution Attendance Quiz Are you here today? Here! (a) yes (b) no (c) my views are evolving on the subject Today s Topics Stellar Evolution An alien visits Earth for a day A star s mass

More information

class 21 Astro 16: Astrophysics: Stars, ISM, Galaxies November 20, 2018

class 21 Astro 16: Astrophysics: Stars, ISM, Galaxies November 20, 2018 Topics: Post-main-sequence stellar evolution, degeneracy pressure, and white dwarfs Summary of reading: Review section 2 of Ch. 17. Read the beginning and first section of Ch. 18 (up through the middle

More information

Stellar Pulsations and Variability

Stellar Pulsations and Variability Chapter 15 Stellar Pulsations and Variability One commonplace of modern astronomy that would have been highly perplexing for ancient astronomers is that many stars vary their light output by detectable

More information

Guiding Questions. The Birth of Stars

Guiding Questions. The Birth of Stars Guiding Questions The Birth of Stars 1 1. Why do astronomers think that stars evolve (bad use of term this is about the birth, life and death of stars and that is NOT evolution)? 2. What kind of matter

More information

Atoms and Star Formation

Atoms and Star Formation Atoms and Star Formation What are the characteristics of an atom? Atoms have a nucleus of protons and neutrons about which electrons orbit. neutrons protons electrons 0 charge +1 charge 1 charge 1.67 x

More information

Probing Stellar Structure with Pressure & Gravity modes the Sun and Red Giants. Yvonne Elsworth. Science on the Sphere 14/15 July 2014

Probing Stellar Structure with Pressure & Gravity modes the Sun and Red Giants. Yvonne Elsworth. Science on the Sphere 14/15 July 2014 Probing Stellar Structure with Pressure & Gravity modes the Sun and Red Giants Yvonne Elsworth Science on the Sphere 14/15 July 2014 Evolving stars are building blocks of the galaxy and their cores are

More information

Guiding Questions. The Deaths of Stars. Pathways of Stellar Evolution GOOD TO KNOW. Low-mass stars go through two distinct red-giant stages

Guiding Questions. The Deaths of Stars. Pathways of Stellar Evolution GOOD TO KNOW. Low-mass stars go through two distinct red-giant stages The Deaths of Stars 1 Guiding Questions 1. What kinds of nuclear reactions occur within a star like the Sun as it ages? 2. Where did the carbon atoms in our bodies come from? 3. What is a planetary nebula,

More information

The Deaths of Stars 1

The Deaths of Stars 1 The Deaths of Stars 1 Guiding Questions 1. What kinds of nuclear reactions occur within a star like the Sun as it ages? 2. Where did the carbon atoms in our bodies come from? 3. What is a planetary nebula,

More information

Lec 7: Classification of Stars, the Sun. What prevents stars from collapsing under the weight of their own gravity? Text

Lec 7: Classification of Stars, the Sun. What prevents stars from collapsing under the weight of their own gravity? Text 1 Astr 102 Lec 7: Classification of Stars, the Sun What prevents stars from collapsing under the weight of their own gravity? Text Why is the center of the Sun hot? What is the source of the Sun s energy?

More information

read 9.4-end 9.8(HW#6), 9.9(HW#7), 9.11(HW#8) We are proceding to Chap 10 stellar old age

read 9.4-end 9.8(HW#6), 9.9(HW#7), 9.11(HW#8) We are proceding to Chap 10 stellar old age HW PREVIEW read 9.4-end Questions 9.9(HW#4), 9(HW#4) 9.14(HW#5), 9.8(HW#6), 9.9(HW#7), 9.11(HW#8) We are proceding to Chap 10 stellar old age Chap 11 The death of high h mass stars Contraction of Giant

More information

Ch. 29 The Stars Stellar Evolution

Ch. 29 The Stars Stellar Evolution Ch. 29 The Stars 29.3 Stellar Evolution Basic Structure of Stars Mass effects The more massive a star is, the greater the gravity pressing inward, and the hotter and more dense the star must be inside

More information

Stellar Evolution: The Deaths of Stars. Guiding Questions. Pathways of Stellar Evolution. Chapter Twenty-Two

Stellar Evolution: The Deaths of Stars. Guiding Questions. Pathways of Stellar Evolution. Chapter Twenty-Two Stellar Evolution: The Deaths of Stars Chapter Twenty-Two Guiding Questions 1. What kinds of nuclear reactions occur within a star like the Sun as it ages? 2. Where did the carbon atoms in our bodies come

More information

Stellar Interior: Physical Processes

Stellar Interior: Physical Processes Physics Focus on Astrophysics Focus on Astrophysics Stellar Interior: Physical Processes D. Fluri, 29.01.2014 Content 1. Mechanical equilibrium: pressure gravity 2. Fusion: Main sequence stars: hydrogen

More information

Sunday, May 1, AGB Stars and Massive Star Evolution

Sunday, May 1, AGB Stars and Massive Star Evolution AGB Stars and Massive Star Evolution Iben The Helium Flash (< 2 Msun) The central core becomes dense enough, that degeneracy pressure dominates over thermal pressure. Still, the core radiates energy and

More information