HR Diagram, Star Clusters, and Stellar Evolution

Size: px
Start display at page:

Transcription

1 Ay 1 Lecture 9 M7 ESO HR Diagram, Star Clusters, and Stellar Evolution

2 9.1 The HR Diagram

3 Stellar Spectral Types Temperature L T Y

4 The Hertzsprung-Russel (HR) Diagram It is a plot of stellar luminosity vs. temperature (~ spectral type)

5 The Hertzsprung-Russel (HR) Diagram Stars form distinctive sequences in the HR diagram This can be understood in the context of the stellar evolution models, and used to test them

6 The Principal Sequences Horizontal Branch They correspond to different stages of the stellar evolution Note: to get the absolute magnitudes (or luminosities), you must have distances

7 The Color-Magnitude Diagram Generally, photometric colors re used on the X axis, as a measure of temperature, e.g., (B-V) = difference in magnitudes in two different filters (B and V) M V Need models of stellar atmospheres to convert these measured quantities into temperatures and bolometric luminosities B-V

8 9.2 Star Clusters: Probes of Stellar Evolution NGC 3603 ESO

9 Star Clusters Open (or Disk): N ~ Ages ~ yr Globular: N ~ Ages ~ Gyr Pleiades Great laboratories for stellar evolution and dynamics Dynamical and evolutionary time scales < or << Galaxy s age, and a broad range of evolutionary states is present M2

10 M25 ESO

11 M13 HST

12 Testing Stellar Evolution The problem: stellar evolution happens on billion-year time scales The solution: use HR Diagrams of star clusters with a wide range of ages Clusters contain 100's to 1000's of stars with a broad mass range All stars are at the same distance, so it is easy to measure their relative luminosities They have the same age, have the same chemical composition Each cluster thus provides a snapshot of what stars of different masses look like at the same age and composition (coeval populations)

13 Open Clusters: HR Diagrams A systematic change with the cluster age: The MS turnoff moves to lower luminosities and temperatures as the cluster ages, and the red giant branch develops

14 Globular Clusters: HR Diagrams Stars above the turnoff have evolved away, and other branches represent the more advanced stages of stellar evolution Horizontal Branch Asymptotic Giant Branch Red Giant Branch We can use that to estimate the ages of the globular clusters, and thus of the Galaxy Turnoff Main Sequence Field stars

15 Globular Cluster Ages Lines: Isochrones = theoretical models of the main sequence and the red giant branch (and others), at a given age, for a given chemical composition Modern value for the mean globular cluster age in our Galaxy:

16 9.3 Star Clusters: Probes of Stellar Dynamics

17 Dynamical Evolution of Star Clusters 1. Internal processes: Dynamical relaxation: stars exchange energies in 2-body interactions, over a relaxation time Stars in the core have lower energies and sink to the bottom of the potential well Core collapse, or gravothermal instability 2. External processes: Tidal shocks and evaporation Stars with higher energies can reach large radii

18 Dynamical Time Scales Open clusters: t c ~ t r < t e quickly dissolved Globular clusters: t c << t r << t e a variety of dynamical evolution states must be present Elliptical galaxies: t c << t r ~ t e dynamical evolution not driven by 2-body relaxation

19 Core Collapse, aka The Gravothermal Catastrophe Core shrinks a little Gets a little hotter, so that E kin balances the increased E pot Faster stars escape Core shrinks some more The only way to arrest the collapse is to provide a source of energy in the center, to replace the escaped heat. In the case of (proto)stars, this is accomplished by thermonuclear reactions. In the case of globular clusters, it is accomplished by hard binaries. log density log radius

20 Binaries as a Source of Energy A binary can either take away or give kinetic energy to a passing star (Numerical simulation by P. Hut and J. Bahcall) Hard binaries (tightly bound) give away more energy than they absorb. They serve as the energy source which arrests the core collapse and stabilize the cluster

21 Globular clusters move in the tidal field of the galaxy. When a star crosses the boundary where the gravitational field of the galaxy is stronger than that of the cluster (the Roche lobe), the star evaporates The same thing happens to stars in open clusters as they pass by the giant molecular clouds in the disk

22 9.4 The Main Sequence

23 Main Sequence (MS) and the Range of Stellar Masses MS is defined as the locus where stars burn H into He in their cores That is where they spend most of their lifetime It is a sequence of stellar masses by far the most dominant parameter that determines stellar properties The lower mass end is set by the objects which cannot reach the necessary [T,ρ] to ignite fusion, because of their low mass (M < 0.08 M ): brown dwarfs (new spectral types: L, T, Y) The high-mass end of the stellar family is set by the Eddington limit

24 Evolution on the Main Sequence Star burns H in core, core composition slowly changes from H to He. Small changes in the external properties (L, T e, R) Main-sequence lifetime is strongly mass-dependent, since the more massive stars: sustain higher core temperatures have higher rates of nuclear fusion are more luminous and exhaust H fuel more quickly L M 3.5 t ms M 2.5 Star leaves the main sequence when it stops burning hydrogen in the core that is now pure He (but it continues burning it in a shell around the core). This leads to expansion of the envelope, and the formation of a red giant

25 Stellar Lifetimes on the Main Sequence

26 Global Stellar Properties Mass essentially determines everything Chemical composition has a relatively minor effect Position of a star in the (L,T) plane also determines its radius, through the Stefan- Boltzmann formula, and thus also the density

27 Differences in Stellar Structures Regarding the Energy Transport Convective core, radiative envelope Radiative core, convective envelope Fully convective

28 Eddington Limit Electrons/ions at a stellar surface feel radiation pressure that is proportional to luminosity, and that can drive a stellar wind When the radiation pressure matches the gravitational pull of the star, we have a limiting, Eddington luminosity: A more luminous star at a given mass would blow itself apart. L = 4πGcm p M σ e M = M sun erg s -1 This is the maximum luminosity which an isotropically emitting source with a mass M could have L Invert the formula: M E = erg s -1 M sun

29 Very Low Mass Stars: Red Dwarfs Mass < 0.4 M Their structure is all convection zone, H and He is mixed throughout the star The star burns H slowly Will never build up a He core, and never ignite He Could perhaps survive on the MS for a 100 Gyr! Then just fade as a White dwarf

30 The End of the MS Phase On the MS, a star is in a hydrostatic equilibrium, and its core is sufficiently hot to fuse H into He Now the star has two chemically distinct zones, a core of inert He surrounded by an H envelope - the core of a MS star is not sufficiently hot for He burning When the core becomes pure He, a new evolutionary phase stars - the ascent to the Red Giant Branch (RGB) Without energy generation, the core cannot support itself against gravitational collapse and so it begins to shrink; as it collapses it heats up This heat is transferred to a thin shell of H around the core which reaches a temperature in which H fusion can occur

31 9.5 Stellar Evolution After the Main Sequence

32 Stellar Evolution Off the Main Sequence Stars of different masses follow different evolutionary tracks on the HR diagram

33 Stellar Evolution is a Sequence of Different Thermonuclear Reactions He burning in the core, H burning in a shell He burning in a shell, H burning in a shell He ignites in the core H burning in a shell H burning in the core

34 Becoming a Red Giant As the core continues to collapse, the temperature in the H fusing shell continues to rise and thus the luminosity in the shell increases as does the pressure The entire star is no longer in a hydrostatic equilibrium, and the envelope begins to expand As they expand these outer layers cool - the star becomes redder, while its luminosity increases: the star slowly ascends the RGB Our Sun will swell to about the size of the Earth s orbit This imbalance will continue until the star again finds a source of core energy generation, i.e., He fusion

35 Structure of a Red Giant Now the core has heated to T ~ 10 8 K, which is the threshold temperature for the fusion of He into C The star is in a quasi-static equilibrium. The lifetime of a star as a Red Giant is about 10% of its MS lifetime The luminosity generated by the core fusion of He into C is far greater than the shell luminosity associated with the fusion of H into He

36 Helium Flash: The End of the RGB H fusion leaves behind He ash in the core of the star which cannot begin to fuse until the temperature of the core reaches 100 million K. How a star begins He fusion depends on its mass: M > 3 M stars contract rapidly, their cores heat up, and He fusion begins gradually Less massive stars evolve more slowly and their cores contract so much that degeneracy occurs in the core When the temperature is hot enough He fusion begins to make energy and the T rises, but pressure does not increase due to degeneracy Higher T increases He fusion even further resulting in a runaway explosion: the Helium Flash which for a few minutes can generate more luminosity than an entire galaxy. The flash does not destroy the star: the envelope absorbs the energy

37 The Next Step: Burning Helium Into Carbon Requires much higher temperatures, T ~ 10 8 K Enabled by the exact right energy resonance for carbon

38 Dredge-ups bring the products of nuclear fusion to a giant star s surface As a low-mass star ages, convection occurs over a larger portion of its volume This takes heavy elements formed in the star s interior and distributes them throughout the star

39 How Long Does it Take?

40 The End Phases of Stellar Evolution The evolution and eventual fate of stars critically dependent on their mass: Stars with initial masses of less than ~ 8 M end as white dwarfs. The star sheds its RG envelope, which becomes a planetary nebula, and the inert, degenerate core cools passively Stars with initial masses greater than ~ 8 M explode as supernovae. The stellar remnants are neutron stars or black holes The fate of our Sun

41 Planetary Nebula Formation A RG brightens by a factor of between 1,000 and 10,000. The outer, hydrogen-rich envelope swells up to a few au radius, with T ~ 2,000-3,000 K A strong stellar wind begins to blow from the star's surface (akin to the Sun's solar wind, but much stronger), and, in the course of the star's RG life, carries away most of the H envelope During the final shedding of its envelope, when the mass loss is the greatest, the star becomes unstable and pulsates, with periods ~ few months to > 1 yr. Such stars are called long-period variables. The envelope material ejected by the star forms an expanding shell of gas that is known as a planetary nebula (PN)

42 Formation of Planetary Nebula Planetary nebulae typically have masses ~ 0.2 M, although some are considerably more massive. They expand V ~ km/s, and plow into the surrounding interstellar medium, contributing to its chemical enrichment. Their central stars (degenerate cores of progenitors) provide photoionization for the nebulae.

43 Planetary Nebulae Imaged by the HST

44 Highly Evolved Star Structure

45 In the last stages, a high-mass star has an Fe-rich core surrounded by concentric shells hosting the various thermonuclear reactions The sequence of thermonuclear reactions stops here, because the formation of elements heavier than Fe requires an input of energy rather than causing energy to be released

46 Rapid Final Stages of a Massive Star Evolution A high mass star undergoes an extended sequence of thermonuclear reactions in its core and shells: C fusion, Ne fusion, O fusion, and Si fusion, all the way to Fe

47 From Birth to Death Processed material returns into the ISM

Lifespan on the main sequence. Lecture 9: Post-main sequence evolution of stars. Evolution on the main sequence. Evolution after the main sequence

Lecture 9: Post-main sequence evolution of stars Lifetime on the main sequence Shell burning and the red giant phase Helium burning - the horizontal branch and the asymptotic giant branch The death of

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

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

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

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

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

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

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

17.1 Lives in the Balance. Our goals for learning: How does a star's mass affect nuclear fusion?

Stellar Evolution 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 nuclear fusion? Stellar Mass and Fusion The mass of a main-sequence

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

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

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

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

Introduction to Astronomy. Lecture 8: The Death of Stars White Dwarfs, Neutron Stars, and Black Holes

Introduction to Astronomy Lecture 8: The Death of Stars White Dwarfs, Neutron Stars, and Black Holes Continued from Last Week Lecture 7 Observing Stars Clusters of stars Some clouds start breaking into

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:

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

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

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

Stellar Evolution and the HertzsprungRussell Diagram 7/14/09. Astronomy 101

Stellar Evolution and the HertzsprungRussell Diagram 7/14/09 Astronomy 101 Astronomy Picture of the Day Astronomy 101 Outline for Today Astronomy Picture of the Day News Articles Business Return Lab 5

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,

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,

Stars: Their Life and Afterlife

The 68 th Compton Lecture Series Stars: Their Life and Afterlife Lecture 3: The Life and Times of Low Mass Stars Brian Humensky, lecturer http://kicp.uchicago.edu/~humensky/comptonlectures.htm October

Lecture 7: Stellar evolution I: Low-mass stars

Lecture 7: Stellar evolution I: Low-mass stars Senior Astrophysics 2018-03-21 Senior Astrophysics Lecture 7: Stellar evolution I: Low-mass stars 2018-03-21 1 / 37 Outline 1 Scaling relations 2 Stellar

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

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

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 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,

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

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?

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

Exam # 3 Tue 12/06/2011 Astronomy 100/190Y Exploring the Universe Fall 11 Instructor: Daniela Calzetti

Exam # 3 Tue 12/06/2011 Astronomy 100/190Y Exploring the Universe Fall 11 Instructor: Daniela Calzetti INSTRUCTIONS: Please, use the `bubble sheet and a pencil # 2 to answer the exam questions, by marking

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

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

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

Lecture 16: Evolution of Low-Mass Stars Readings: 21-1, 21-2, 22-1, 22-3 and 22-4

Lecture 16: Evolution of Low-Mass Stars Readings: 21-1, 21-2, 22-1, 22-3 and 22-4 For the protostar and pre-main-sequence phases, the process was the same for the high and low mass stars, and the main

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

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

AST 101 Introduction to Astronomy: Stars & Galaxies

The H-R Diagram review So far: AST 101 Introduction to Astronomy: Stars & Galaxies - Stars on Main Sequence (MS) - Pre MS (Star Birth) Next: - Post MS: Giants, Super Giants, White dwarfs Evolution of Low

Beyond the Solar System 2006 Oct 17 Page 1 of 5

I. Stars have color, brightness, mass, temperature and size. II. Distances to stars are measured using stellar parallax a. The further away, the less offset b. Parallax angles are extremely small c. Measured

10/29/2009. The Lives And Deaths of Stars. My Office Hours: Tuesday 3:30 PM - 4:30 PM 206 Keen Building. Stellar Evolution

of s Like s of Other Stellar The Lives And Deaths of s a Sun-like s More 10/29/2009 My Office Hours: Tuesday 3:30 PM - 4:30 PM 206 Keen Building Test 2: 11/05/2009 of s Like s of Other a Sun-like s More

Lecture 33: The Lives of Stars

Lecture 33 The Lives of Stars Astronomy 141 Winter 2012 This lecture concerns the life cycle of normal stars. Stars shine because they are hot, and need a source of energy to keep shining. Main Sequence

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

20. Stellar Death. Interior of Old Low-Mass AGB Stars

20. Stellar Death Low-mass stars undergo three red-giant stages Dredge-ups bring material to the surface Low -mass stars die gently as planetary nebulae Low -mass stars end up as white dwarfs High-mass

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,

Lecture Outlines. Chapter 20. Astronomy Today 8th Edition Chaisson/McMillan Pearson Education, Inc.

Lecture Outlines Chapter 20 Astronomy Today 8th Edition Chaisson/McMillan Chapter 20 Stellar Evolution Units of Chapter 20 20.1 Leaving the Main Sequence 20.2 Evolution of a Sun-Like Star 20.3 The Death

AST 101 Introduction to Astronomy: Stars & Galaxies

AST 101 Introduction to Astronomy: Stars & Galaxies The H-R Diagram review So far: Stars on Main Sequence (MS) Next: - Pre MS (Star Birth) - Post MS: Giants, Super Giants, White dwarfs Star Birth We start

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

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

NSCI 314 LIFE IN THE COSMOS

NSCI 314 LIFE IN THE COSMOS 2 BASIC ASTRONOMY, AND STARS AND THEIR EVOLUTION Dr. Karen Kolehmainen Department of Physics CSUSB COURSE WEBPAGE: http://physics.csusb.edu/~karen MOTIONS IN THE SOLAR SYSTEM

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

Reading and Announcements. Read Chapter 14.1, 14.2 Homework #6 due Tuesday, March 26 Exam #2, Thursday, March 28

Reading and Announcements Read Chapter 14.1, 14.2 Homework #6 due Tuesday, March 26 Exam #2, Thursday, March 28 The life of the Sun The Sun started as a cloud of gas. Gravity caused the cloud to collapse.

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

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

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

Astronomy 1504 Section 002 Astronomy 1514 Section 10 Midterm 2, Version 1 October 19, 2012

Astronomy 1504 Section 002 Astronomy 1514 Section 10 Midterm 2, Version 1 October 19, 2012 Choose the answer that best completes the question. Read each problem carefully and read through all the answers.

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

Protostars evolve into main-sequence stars

Understanding how stars evolve requires both observation and ideas from physics The Lives of Stars Because stars shine by thermonuclear reactions, they have a finite life span That is, they fuse lighter

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

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

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

Lecture 8: The Death of Stars White Dwarfs, Neutron Stars, and Black Holes

Lecture 8: The Death of Stars White Dwarfs, Neutron Stars, and Black Holes ! the time a star is fusing hydrogen into helium in its core! stars spend most of their time in this stage! main-sequence stars

Astronomy 113. Dr. Joseph E. Pesce, Ph.D. Dr. Joseph E. Pesce, Ph.D.

Astronomy 113 Dr. Joseph E. Pesce, Ph.D. Stellar Deaths/Endpoints 13-2 Low Mass Stars ³ Like the Sun (< 2 M ) ² Live about 10 billion years (sun is middle aged) ² Create elements through Carbon, Nitrogen,

Lecture 24: Testing Stellar Evolution Readings: 20-6, 21-3, 21-4

Lecture 24: Testing Stellar Evolution Readings: 20-6, 21-3, 21-4 Key Ideas HR Diagrams of Star Clusters Ages from the Main Sequence Turn-off Open Clusters Young clusters of ~1000 stars Blue Main-Sequence

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

What is a star? A body of gases that gives off tremendous amounts of energy in the form of light & heat. What star is closest to the earth?

Stars What is a star? A body of gases that gives off tremendous amounts of energy in the form of light & heat. What star is closest to the earth? Answer: The SUN It s about 150,000,000 km from earth =

PHYS 1401: Descriptive Astronomy Notes: Chapter 12

CHAPTER 12: STELLAR EVOLUTION 12.1: LEAVING THE MAIN SEQUENCE Stars and the Scientific Method You cannot observe a single star from birth to death You can observe a lot of stars in a very short period

The Life and Death of Stars

The Life and Death of Stars What is a Star? A star is a sphere of plasma gas that fuses atomic nuclei in its core and so emits light The name star can also be tagged onto a body that is somewhere on the

Chapter 14. Stellar Evolution I. The exact sequence of evolutionary stages also depends on the mass of a star.

Chapter 14 Stellar Evolution I I. Introduction Stars evolve in the sense that they pass through different stages of a stellar life cycle that is measured in billions of years. The longer the amount of

Stellar Evolution: After the Main Sequence. Chapter Twenty-One

Stellar Evolution: After the Main Sequence Chapter Twenty-One Guiding Questions 1. How will our Sun change over the next few billion years? 2. Why are red giants larger than main-sequence stars? 3. Do

Stellar Evolution: After the Main Sequence. Guiding Questions. Chapter Twenty-One

Stellar Evolution: After the Main Sequence Chapter Twenty-One Guiding Questions 1. How will our Sun change over the next few billion years? 2. Why are red giants larger than main-sequence stars? 3. Do

Prentice Hall EARTH SCIENCE

Prentice Hall EARTH SCIENCE Tarbuck Lutgens Chapter 25 Beyond Our Solar System 25.1 Properties of Stars Characteristics of Stars A constellation is an apparent group of stars originally named for mythical

Stellar Evolution: After the Main Sequence. Chapter Twenty-One. Guiding Questions

Stellar Evolution: After the Main Sequence Chapter Twenty-One Guiding Questions 1. How will our Sun change over the next few billion years? 2. Why are red giants larger than main-sequence stars? 3. Do

Nuclear Physics and Astrophysics of Exploding Stars

Nuclear Physics and Astrophysics of Exploding Stars Lars Bildsten Kavli Institute for Theoretical Physics Department of Physics University of California, Santa Barbara Dan Kasen (UCSC), Kevin Moore (UCSB),

Lecture 21 Formation of Stars November 15, 2017

Lecture 21 Formation of Stars November 15, 2017 1 2 Birth of Stars Stars originally condense out of a COLD, interstellar cloud composed of H and He + trace elements. cloud breaks into clumps (gravity)

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

Comparing a Supergiant to the Sun

The Lifetime of Stars Once a star has reached the main sequence stage of it life, it derives its energy from the fusion of hydrogen to helium Stars remain on the main sequence for a long time and most

Announcement: Quiz Friday, Oct 31

Announcement: Quiz Friday, Oct 31 What is the difference between the giant, horizontal, and asymptotic-giant branches? What is the Helium flash? Why can t high-mass stars support themselves in hydrostatic

Ch. 16 & 17: Stellar Evolution and Death

Ch. 16 & 17: Stellar Evolution and Death Stars have lives: born, evolve, die Mass determines stellar evolution: Really Low Mass (0.08 to 0.4 M sun ) Low Mass: (0.4 to 4 M sun ) Long lives High Mass (4

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

Today. Stars. Evolution of High Mass Stars. Nucleosynthesis. Supernovae - the explosive deaths of massive stars

Today Stars Evolution of High Mass Stars Nucleosynthesis Supernovae - the explosive deaths of massive stars 1 Another good job on exam! Class average was 71% Given the difficulty of the exam, this was

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

Evolution of High Mass Stars

Luminosity (L sun ) Evolution of High Mass Stars High Mass Stars O & B Stars (M > 4 M sun ): Burn Hot Live Fast Die Young Main Sequence Phase: Burn H to He in core Build up a He core, like low-mass stars

Exam #2 Review Sheet. Part #1 Clicker Questions

Exam #2 Review Sheet Part #1 Clicker Questions 1) The energy of a photon emitted by thermonuclear processes in the core of the Sun takes thousands or even millions of years to emerge from the surface because

(2) low-mass stars: ideal-gas law, Kramer s opacity law, i.e. T THE STRUCTURE OF MAIN-SEQUENCE STARS (ZG: 16.2; CO 10.6, 13.

6.1 THE STUCTUE OF MAIN-SEQUENCE STAS (ZG: 16.2; CO 10.6, 13.1) main-sequence phase: hydrogen core burning phase zero-age main sequence (ZAMS): homogeneous composition Scaling relations for main-sequence

5) What spectral type of star that is still around formed longest ago? 5) A) F B) A C) M D) K E) O

HW2 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) The polarization of light passing though the dust grains shows that: 1) A) the dust grains

ASTRONOMY 1 EXAM 3 a Name

ASTRONOMY 1 EXAM 3 a Name Identify Terms - Matching (20 @ 1 point each = 20 pts.) Multiple Choice (25 @ 2 points each = 50 pts.) Essays (choose 3 of 4 @ 10 points each = 30 pt 1.Luminosity D 8.White dwarf

Evolution of Stars Population III: Population II: Population I:

Evolution of Stars 1. Formed from gas/dust cloud collapse from gravity 2. Fuse H to He on the Main Sequence. Then evolve off Main-sequence as they burn He and successive elements. 3. When nuclear fusion

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

Stars, Galaxies & the Universe Announcements. Stars, Galaxies & the Universe Lecture Outline. HW#7 due Friday by 5 pm! (available Tuesday)

Stars, Galaxies & the Universe Announcements HW#7 due Friday by 5 pm! (available Tuesday) Midterm Grades (points) posted today in ICON Exam #2 next week (Wednesday) Review sheet and study guide posted

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

Gravity simplest. fusion

Gravity simplest fusion The life of a star has a complex relationship with gravity: 1. Gravity is what brings the original dust together to make a star 2. Gravity wants to crush the star Gravity pulls

Stages of the Sun's life:

Stellar Evolution Stages of the Sun's life: 1) initial collapse from interstellar gas (5 million yrs) 2) onset of nuclear reactions to start of main sequence phase (30 million yrs) 3) main sequence (10

Lecture 24. Reprise: Evolution Timescale

Lecture 24 Life as a Low Mass Giant Dating the Stars Shell vs Core Fusion Helium Fusion Planetary Nebulae Mar 22, 2006 Astro 100 Lecture 24 1 Reprise: Evolution Timescale To estimate the duration of any

Announcements. L! m 3.5 BRIGHT FAINT. Mass Luminosity Relation: Why? Homework#3 will be handed out at the end of this lecture.

Announcements BRIGHT Homework#3 will be handed out at the end of this lecture. Due October 14 (next Thursday) Review of Mid-term exam will be handed out Tuesday. Mid-term exam will be variants (if not

Stellar Models ASTR 2110 Sarazin

Stellar Models ASTR 2110 Sarazin Jansky Lecture Tuesday, October 24 7 pm Room 101, Nau Hall Bernie Fanaroff Observing the Universe From Africa Trip to Conference Away on conference in the Netherlands

25.2 Stellar Evolution. By studying stars of different ages, astronomers have been able to piece together the evolution of a star.

25.2 Stellar Evolution By studying stars of different ages, astronomers have been able to piece together the evolution of a star. Star Birth The birthplaces of stars are dark, cool interstellar clouds,

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

Gravitational collapse of gas

Gravitational collapse of gas Assume a gas cloud of mass M and diameter D Sound speed for ideal gas is c s = γ P ρ = γ nkt ρ = γ kt m Time for sound wave to cross the cloud t sound = D == D m c s γ kt

How Do Stars Appear from Earth?

How Do Stars Appear from Earth? Magnitude: the brightness a star appears to have from Earth Apparent Magnitude depends on 2 things: (actual intrinsic brightness) The color of a star is related to its temperature:

Lec 9: Stellar Evolution and DeathBirth and. Why do stars leave main sequence? What conditions are required for elements. Text

1 Astr 102 Lec 9: Stellar Evolution and DeathBirth and Evolution Why do stars leave main sequence? What conditions are required for elements Text besides Hydrogen to fuse, and why? How do stars die: white

Supernova events and neutron stars

Supernova events and neutron stars So far, we have followed stellar evolution up to the formation of a C-rich core. For massive stars ( M initial > 8 M Sun ), the contracting He core proceeds smoothly