Astronomy. Stellar Evolution
|
|
- Darlene Parker
- 6 years ago
- Views:
Transcription
1 Astronomy A. Dayle Hancock 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 stage fusion H-R diagrams for star cluster in the later stages of evolution Two kinds of stellar populations Pulsating older stars How stars in binary systems evolve differently physics.wm.edu/~hancock/171/ 1
2 Life on the Main Sequence A main sequence star is a star that has a core which is 'burning' hydrogen by nuclear fusion. It is in hydrostatic equilibrium (the outward pressure of the fusion core is balanced by the inward pull of gravity). Stars on the main sequence have a main sequence lifetime. For the Sun this is about 12 billion years. A newly formed main sequence star is called a zero-age main sequence star. Over their lifetime on the main sequence, stars undergo changes as the hydrogen fuel is 'burned' in the star's core. As we have seen, new main sequence stars start with 74% hydrogen, 25% helium and 1% heavy elements. 2
3 Life on the Main Sequence The Sun is almost ½ way through its lifetime. The graphs show the composition of the Sun as a function of distance from the center. 4.5 billion years ago the Sun had 75% hydrogen at the center but now is about 35%. The helium was originally at 25% but is now 65% of the mass at the center. 3
4 Life on the Main Sequence As 4 H are converted into 1 He in the core, the number of nuclei in the core is reduced and the core shrinks. This increases the temperature and density in the core. As the core shrinks, outer layers of the Sun expand and shine more brightly. Because the core is hotter and denser more fusion occurs. The increased energy causes the increased luminosity. Over the last 4.56 billion year the Sun has become 40% more luminous and the radius has increased by 6%. 4
5 Life on the Main Sequence For small mass stars (0.08 to 0.4 Mⵙ the situation is different. This spectral class M stars are called red dwarfs. They are small and are 'red' because of their low temperature. They account for 85% of all stars. In red dwarf stars, convection cells extend into the core and move helium out of the core and hydrogen into the core. Over the lifetime of a red dwarf, the star converts all of its hydrogen to helium. Since a red dwarf is small the fusion process is slower. Calculations indicate red dwarfs live for hundreds of billions of years. This is longer than the age of the universe. No red dwarf has ever converted all of its hydrogen into helium. 5
6 Lifetimes of Main Sequence Stars The lifetime of a main sequence star depends on its mass. Massive stars are more luminous and have short life times Less massive stars are less luminous and have longer lifetime. The relationship between mass and lifetime is given by: 1 t 2.5 M where M is the mass in Mⵙ and t is given in Sun lifetimes of 1.2 x 1010 years. 6
7 Red Giants A star <0.4 Mⵙ will eventually (100s of billions of years) will use all of its hydrogen and become a ball of helium. A star >0.4 Mⵙ like the Sun will become a red giant. After the core hydrogen is used up, fusion continues in the hydrogen-rich shell outside of the core (shell hydrogen fusion). The burnt-out core will heat up from gravitational contraction. This increases the shell hydrogen burning. The helium falls into the core which contract more and heat up further. The core of a 1 Mⵙ star will contract to 1/3 its original size. The outer shells expands as the shell hydrogen fusion 'eats' its way outward into the surrounding material. The luminosity increase due to the larger size. 7
8 Red Giants The surface temperature of the red giant drops. The core (mainly helium) increases from 15 million degrees to ~100 million degrees. Because of the large size, the gravity is weaker in the out regions. Mass escapes from the star. As much as 10-7 Mⵙ per year can escape. This compares to a 1 Mⵙ star like the Sun of Mⵙ per year. 8
9 The distant Future of the Solar System The Sun's luminosity will continue to increase. In 1.3 billion years, the temperature of the Earth will increase to 50oC. In 3 ½ billion years the temperature of Earth will be higher than the boiling point of water. The Earth will become uninhabitable. After another 7 billion years the Sun will finish converting hydrogen to helium in its core and the sun will move off of the main sequence and become a red giant. After 700 million years the Sun will have expanded to a radius of 1 AU with a surface temperature of 3500 K. Mercury, Venus and Earth will be vaporized inside of the Sun. The Jovian planets will lose their outer atmospheres leaving only their tiny rocky cores. 9
10 Fusion of Helium into Carbon and Oxygen A young red giant star (>0.4 Mⵙ ) has a helium core with no thermonuclear reactions. Shell hydrogen fusion is the source of the red giant's energy. When the helium core (helium ash) become highly compressed and hot (100 million degrees), helium fusion can take place: He + 4He 8Be 4 10
11 Fusion of Helium into Carbon and Oxygen Be (beryllium) is very unstable with a half life of 7 x s. Because the helium core is so dense and hot, there is a significant possibility the 8 Be will collide with another 4He. This then produced 12C through the triple alpha process: 8 Be + 4He 12C + γ Where the γ is a high energy gamma ray photon. The process can continue with: 8 C + 4He 16O+ γ 12 11
12 Helium Flash and Electron Degeneracy For stars with > 0.4 Mⵙ and < 2-3 Mⵙ helium fusion begins suddenly in what is called the helium flash. At the density and temperature of the helium core, the material is ionized into nuclei and electrons. The electrons are so tightly compressed they obey the Pauli exclusion principle. The Pauli exclusion principle state two fermion particles can not be in the same energy state. Just before the helium fusion begins the electrons are so densely packed they exert a strong force to resist further compression known as degenerate electron pressure. As the helium fusion begins this heats the core but the core can not expand and cool which causes the helium fusion to proceed quickly the helium flash. Eventually the electrons become so hot they are no longer degenerate and the core can expand. 12
13 Continued Evolution of a Red Giant After the helium flash, the stars luminosity decreases because of core expands and reduces the hydrogen shell fusion. Temperature and luminosity drops. The outer layers contract leaving a star with less luminosity, smaller and with a higher surface temperature. For a 1 Mⵙ star, helium fusion only last for about 108 years compared to its 12 billion years on the main sequence. 13
14 H-R Diagrams and Red Giant Evolution This zero age main sequence (ZAMS) H-R diagram shows what various mass stars do when they the have exhausted the hydrogen in their cores and leave the main sequence at the dashed line. High mass stars move quickly from left to right maintaining their luminosity as their temperature decrease. After helium core fusion begins their luminosity peaks. For lower mass stars, helium core fusion starts with a helium flash and the luminosity decreases. 14
15 Clusters and Stellar Evolution These H-R diagrams show the evolution of stars which start in the same star cluster. Stars of different masses all begin in the cluster as protostars. Th more massive stars approach the main sequence faster than the smaller stars. 15
16 Clusters and Stellar Evolution After 3 million years most of the massive stars are main sequence stars. After 30 million years some of the massive starts have used up their hydrogen and are red giants while the less massive stars are approaching the main sequence. After 66 million years more of the main sequence stars have become red giants. 16
17 Clusters and Stellar Evolution After 100 million years, many stars > 1 Mⵙ have ended hydrogen core fusion and have moved to become red giants. After 4.5 billion years, only the smaller stars remain on the main sequence. 17
18 Real Clusters These two open star clusters have different ages. The lower cluster (NGC 2158) has no blue stars which indicates it contains only smaller stars and stars that have become red giants and is much older. The M35 cluster has many blue stars and is much younger (150 million years). 18
19 Clusters and Stellar Evolution This globular cluster contains a few hundred million stars in a region only 20 pc across. Globular clusters are old because they contain no high mass main sequence stars. This globular cluster contains red giants and horizontal branch stars with helium fusion and shell hydrogen fusion. 19
20 Measuring the Age of Clusters The age of a star cluster can be found from the turn off point. The turn off point is where there are no more high mass main sequence stars. The lower down the turn off point, the older the cluster. 20
21 Population I and II stars. Star clusters show the difference between the oldest and youngest stars. Population I stars have strong absorption line for metals. Population II stars show very weak absorption lines of metals. The early universe contained only H and He and very small amounts of metals. Population II stars formed out of this material and are the oldest stars. Second generation population II stars formed from nebula with fusion produced metals and are younger stars. The Sun and solar system formed from material with 12C, 16O etc. produced by helium fusion in ancient stars. 21
22 Pulsating Stars Some stars pulsate. Their intensity will change over long or short periods of time. The image show the variation in the long period variable star Mira. At its maximum luminosity, Mira is 100 times a bright as when it at its minimum. Mira's period is 332 days. It has a surface temperature of 3500 K. Long period variables have luminosities of 10 10,000 L ⵙ. The radius also increases with its luminosity. The details of a long period variable are not completely understood. Note: the image just shows brightness, not radius. 22
23 Cepheid Variable Stars Pulsating stars are located in the upper right of a H-R diagram. Cepheid variables (named after δ Celhei) have shorter periods of days to months. Cepheids are located in the instability strip where main sequence stars are becoming red giants. This is the region where helium fusion has started. As the star passes through this region its brightness varies periodically. 23
24 Cepheid Variable Stars δ Celhei was discovered in 1784 and pulsates with a period of 5.4 days (top image). In 1894 Doppler shifting of its spectrum showed the surface of the surface was expanding at maximum brightness and contracting at minimum brightness over the same 5.4 day period. 24
25 Cepheid Variable Stars When δ Celhei is at its maximum brightness, the surface temperature is at a maximum. At its maximum brightness diameter is expanding. 25
26 Cepheid Variable Stars What makes a Cepheid variable star pulsate? Eddington suggested that Cepheids pulsate because they are more opaque when compressed. This increases the temperature because of trapped heat energy and the star expands. As it expands, the heat can escape, the internal pressure drops and the star collapses. In the 1960s, John Cox showed that helium was the cause. Normally unionized helium is transparent to radiation. In certain outer layers of the Cepheid, compression ionizes the helium instead of just heating it. When the helium becomes ionized it becomes opaque to radiation. This traps the radiation causing the star to expand. As this outer layer expands, it cools and the helium becomes transparent and releases the heat. The stars surface then falls inward. 26
27 Cepheid Variable Stars Cepheids have luminosities of Lⵙ. Plotting the luminosity of a Cepheid vs the Cepheid's period on a log log plot show the period is related to the luminosity. Measuring the period gives the luminosity and knowing the luminosity determines the distance using the inverse square law. With such large luminosities, Cepheid can be used to measure distances to stars millions of pc away even stars in distant galaxies. 27
28 RR Lyrea Variables. Low mass stars do not become variable states. The third type of variable star is the RR Lyrea. These stars have periods of less than a day and luminosities of ~100 Lⵙ. The region on the H-R diagram instability strip for RR Lyrea stars is a segment of the horizontal branch. These are Population II stars and are often found in globular clusters. They have been used to determine distances of stars in the Milky Way in the same way Cepheids are used to find distances to stars in other galaxies. 28
29 Mass transfer in Binary Systems Binary systems can effect stellar evolution. In a binary system where the stars are far apart, both stars are nearly perfect sphere. In a close binary, the mathematical surface which defines the gravitational domain of each star is call the Roche surface. Tidal forces can distort the stars surface in a close binary. The Lagrangian point is where the two Roche surfaces touch in a close binary. Gravity and rotational forces balance at the Lagrangian point. In a semidetached binary, one star fills its Roche lobe (surface). 29
30 Mass transfer in Binary Systems In a contact binary system, both stars fill their Roche lobe. Mass can flow from either star into the other star across the Lagrangian point. If both stars are so close they overfill their Roche lobe (overcontact binary), the stars can share their outer atmospheres. 30
31 Observation of Mass transfer If the binary systems orbital plane is edge-on from our viewpoint, eclipses of the stars can be seen. In the case of the semi-detached binary Algol system, the variation in intensity is because of the more luminous main sequence star eclipsing the larger red giant. 31
32 Observation of Mass transfer In the β Lyrea semi-detached binary system, the less massive β Lyrea fills its Roche lobe but the more massive binary companion is enveloped in an accretion disk of gas being captured by β Lyrea. Eventually, the detached star will fill its Roche lobe and they system will become an over-contact binary system. 32
33 Observation of Mass transfer W Ursae Majois is an example of an over contact binary system where the two star share a common outer atmosphere. 33
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
More informationStellar 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
More informationStellar 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
More informationGuiding 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 informationUniverse. Chapter 19. Stellar Evolution: On and After the Main Sequence 8/13/2015. By reading this chapter, you will learn
Roger Freedman Robert Geller William Kaufmann III Universe Tenth Edition Chapter 19 Stellar Evolution: On and After the Main Sequence By reading this chapter, you will learn 19 1 How a main sequence star
More informationChapter 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 informationLife 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 informationGuiding 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 informationAstronomy 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 informationAstronomy 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 informationHeading 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 informationProtostars 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
More informationChapter 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 informationHR 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 informationChapter 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 informationASTR-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 informationStellar Midlife. A. Main Sequence Lifetimes. (1b) Lifetime of Sun. Stellar Evolution Part II. A. Main Sequence Lifetimes. B. Giants and Supergiants
Stellar Evolution Part II 1 Stellar Midlife 2 Stellar Midlife A. Main Sequence Lifetimes B. Giants and Supergiants C. Variables (Cepheids) Dr. Bill Pezzaglia Updated Oct 9, 2006 A. Main Sequence Lifetimes
More informationStars, 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
More informationLifespan 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
More informationLecture 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
More informationThe 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 informationThe 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 informationExam # 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
More informationEvolution 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
More informationLecture 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 informationBrought to you in glorious, gaseous fusion-surround. Intro to Stars Star Lives 1
Brought to you in glorious, gaseous fusion-surround. Intro to Stars Star Lives 1 Stellar Evolution Stars are born when fusion reactions begin. Along the way they evolve, i.e. change. Stars die when fusion
More informationASTR-101 4/4/2018 Stellar Evolution: Part II Lecture 19
ASTR-101 4/4/2018 Stellar Evolution: Part II Lecture 19 WHEN S THE NEXT TEST?!?!?!? If anyone is following the syllabus, you know that it says there is a test today. The test will be on April 11 th (a
More informationThe 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 informationChapter 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 informationAST 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
More informationStars 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 informationAstronomy 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.
More informationAST 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
More informationChapter 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 informationBefore 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 informationStellar 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 informationComparing 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
More informationReview: 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 informationLecture 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
More informationWhat 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 =
More information5) 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
More informationThe Life of Our Sun The Life of Our Sun
The Life of a Star Chapter 14 Stellar Evolution 1 2 Mass Is the Key Stars require millions to billions of years to evolve a time that is incredibly slow by human standards A star s evolution can be studied
More informationChapter 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
More informationChapter 15: Surveying the Stars
Chapter 15 Lecture Chapter 15: Surveying the Stars Surveying the Stars 15.1 Properties of Stars Our goals for learning: How do we measure stellar luminosities? How do we measure stellar temperatures? How
More informationThe Night Sky. The Universe. The Celestial Sphere. Stars. Chapter 14
The Night Sky The Universe Chapter 14 Homework: All the multiple choice questions in Applying the Concepts and Group A questions in Parallel Exercises. Celestial observation dates to ancient civilizations
More informationNotes for Wednesday, July 16; Sample questions start on page 2 7/16/2008
Notes for Wednesday, July 16; Sample questions start on page 2 7/16/2008 Wed, July 16 MW galaxy, then review. Start with ECP3Ch14 2 through 8 Then Ch23 # 8 & Ch 19 # 27 & 28 Allowed Harlow Shapely to locate
More informationLIFE CYCLE OF A STAR
LIFE CYCLE OF A STAR First stage = Protostar PROTOSTAR Cloud of gas and dust many light-years across Gravity tries to pull the materials together Eventually, at the center of the ball of dust and gas,
More informationBeyond 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
More informationStages 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
More informationOutline - 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 informationChapter 15 Surveying the Stars
Chapter 15 Surveying the Stars 15.1 Properties of Stars Our goals for learning How do we measure stellar luminosities? How do we measure stellar temperatures? How do we measure stellar masses? How do we
More informationA 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 informationThe Cosmic Perspective. Surveying the Properties of Stars. Surveying the Stars. How do we measure stellar luminosities?
Surveying the Stars Chapter 15 Lecture The Cosmic Perspective 15.1 Properties of Stars Our goals for learning: How do we measure stellar luminosities? How do we measure stellar temperatures? How do we
More informationCh. 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 informationAST 101 INTRODUCTION TO ASTRONOMY SPRING MIDTERM EXAM 2 TEST VERSION 1 ANSWERS
AST 101 INTRODUCTION TO ASTRONOMY SPRING 2008 - MIDTERM EXAM 2 TEST VERSION 1 ANSWERS Multiple Choice. In the blanks provided before each question write the letter for the phrase that best answers the
More informationExam 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 informationSelected Questions from Minute Papers. Outline - March 2, Stellar Properties. Stellar Properties Recap. Stellar properties recap
Black Holes: Selected Questions from Minute Papers Will all the material in the Milky Way eventually be sucked into the BH at the center? Does the star that gives up mass to a BH eventually get pulled
More informationLIFE CYCLE OF A STAR
LIFE CYCLE OF A STAR First stage = Protostar PROTOSTAR Cloud of gas and dust many light-years across Gravity tries to pull the materials together Eventually, at the center of the ball of dust and gas,
More information1. 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 information10/29/2009. 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
More informationAstronomy 104: Second Exam
Astronomy 104: Second Exam Stephen Lepp October 29, 2014 Each question is worth 2 points. Write your name on this exam and on the scantron. Short Answer A The Sun is powered by converting hydrogen to what?
More informationStellar 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 informationChapter 15 Surveying the Stars Properties of Stars
Chapter 15 Surveying the Stars 15.1 Properties of Stars Our goals for learning: How do we measure stellar luminosities? How do we measure stellar temperatures? How do we measure stellar masses? Luminosity:
More informationEvolution 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 informationNSCI 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
More informationPhys 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 informationChapter 15 Lecture. The Cosmic Perspective Seventh Edition. Surveying the Stars Pearson Education, Inc.
Chapter 15 Lecture The Cosmic Perspective Seventh Edition Surveying the Stars 15.1 Properties of Stars Our goals for learning: How do we measure stellar luminosities? How do we measure stellar temperatures?
More informationAstronomy 122 Midterm
Astronomy 122 Midterm This Class (Lecture 15): Stellar Evolution: The Main Sequence Next Class: Stellar Evolution: Post-Main Sequence Midterm on Thursday! Last week for Nightlabs 1 hour exam in this classroom
More informationStars with Mⵙ go through two Red Giant Stages
Astronomy A. Dayle Hancock adhancock@wm.edu Small 239 Office hours: MTWR 10-11am Death of Stars Nuclear reactions in small stars How stars disperse carbon How low mass stars die The nature of white dwarfs
More informationDistance Measuring Techniques and The Milky Way Galaxy
Distance Measuring Techniques and The Milky Way Galaxy Measuring distances to stars is one of the biggest challenges in Astronomy. If we had some standard candle, some star with a known luminosity, then
More informationChapter 15 Surveying the Stars Pearson Education, Inc.
Chapter 15 Surveying the Stars 15.1 Properties of Stars Our goals for learning: How do we measure stellar luminosities? How do we measure stellar temperatures? How do we measure stellar masses? 1. How
More informationLife 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 informationAstro 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 informationHigh 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 information10/26/ 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 informationStellar 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 informationThe Universe. is space and everything in it.
The Universe is space and everything in it. Galaxies A galaxy is a supercluster of stars, gas, and dust that are held together by gravity. There are three main types of galaxies: Irregular Elliptical Spiral
More information7/9. What happens to a star depends almost completely on the mass of the star. Mass Categories: Low-Mass Stars 0.2 solar masses and less
7/9 What happens to a star depends almost completely on the mass of the star. Mass Categories: Low-Mass Stars 0.2 solar masses and less Medium-Mass Stars 0.2 solar masses up to between 2 and 3 solar masses.
More informationStars and Galaxies 1
Stars and Galaxies 1 Characteristics of Stars 2 Star - body of gases that gives off great amounts of radiant energy as light and heat 3 Most stars look white but are actually different colors Antares -
More information10/17/2012. 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 informationGravitational 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
More informationAstro 21 first lecture. stars are born but also helps us study how. Density increases in the center of the star. The core does change from hydrogen to
Astro 21 first lecture The H-R H R Diagram helps us study how stars are born but also helps us study how they die. Stars spend most of their lives as main sequence stars. The core does change from hydrogen
More informationAstronomy 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 informationRecall 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 informationPage 386 SUMMARY. d TABLE 14.2 EVOLUTION OF LOW MASS AND HIGH MASS STARS Low Mass Star (Mass Less Than 8 M ) High Mass Star (Mass More Than 8 M )
Page 386 SUMMARY A star forms from interstellar gas drawn together by gravity, which compresses and heats the gas to form a protostar. Further heating causes the core of the protostar to fuse hydrogen
More informationWhy 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 informationStars & Galaxies. Chapter 27, Section 1. Composition & Temperature. Chapter 27 Modern Earth Science Characteristics of Stars
Stars & Galaxies Chapter 27 Modern Earth Science Chapter 27, Section 1 27.1 Characteristics of Stars Composition & Temperature Scientists use the following tools to study stars Telescope Observation Spectral
More information5) Which stage lasts the longest? a) viii b) I c) iv d) iii e) vi
1) Which of the following statements about globular clusters is false? a) Globular cluster stars are very metal- poor relative to the Sun. b) Globular cluster stars are more than 12 billion years old.
More informationGALAXIES AND STARS. 2. Which star has a higher luminosity and a lower temperature than the Sun? A Rigel B Barnard s Star C Alpha Centauri D Aldebaran
GALAXIES AND STARS 1. Compared with our Sun, the star Betelgeuse is A smaller, hotter, and less luminous B smaller, cooler, and more luminous C larger, hotter, and less luminous D larger, cooler, and more
More informationChapter 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 informationAgenda for Ast 309N, Sep. 27. Measuring Masses from Binary Stars
Agenda for Ast 309N, Sep. 27 Quiz 3 The role of stellar mass Ages of star clusters Exam 1, Thurs. Oct. 4 Study guide out on 9/28 Next topic: brown dwarfs and extrasolar planets 1 This image of the central
More informationASTRONOMY 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
More informationReading 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.
More informationLow-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 informationLate Stages of Stellar Evolution. Late Stages of Stellar Evolution
Late Stages of Stellar Evolution The star enters the Asymptotic Giant Branch with an active helium shell burning and an almost dormant hydrogen shell Again the stars size and luminosity increase, leading
More informationPHYS 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
More informationStellar Evolution: Outline
Stellar Evolution: Outline Interstellar Medium (dust) Hydrogen and Helium Small amounts of Carbon Dioxide (makes it easier to detect) Massive amounts of material between 100,000 and 10,000,000 solar masses
More informationDaily Science 03/30/2017
Daily Science 03/30/2017 The atmospheres of different planets contain different gases. Which planet is most likely Earth? a. planet 1 b. planet 2 c. planet 3 d. planet 4 KeslerScience.com Can you name
More informationDark Matter. About 90% of the mass in the universe is dark matter Initial proposals: MACHOs: massive compact halo objects
1 Dark Matter About 90% of the mass in the universe is dark matter Initial proposals: MACHOs: massive compact halo objects Things like small black holes, planets, other big objects They must be dark (so
More informationPhysics Homework Set 2 Sp 2015
1) A large gas cloud in the interstellar medium that contains several type O and B stars would appear to us as 1) A) a reflection nebula. B) a dark patch against a bright background. C) a dark nebula.
More information