# Lecture 12: Distances to stars. Astronomy 111

Size: px
Start display at page:

Transcription

1 Lecture 12: Distances to stars Astronomy 111

2 Why are distances important? Distances are necessary for estimating: Total energy released by an object (Luminosity) Masses of objects from orbital motions (Kepler s third law) Physical sizes of objects

3 The problem of measuring distances Q: What do you do when an object is out of reach of your measuring instruments? Examples: Surveying & mapping Architecture Any astronomical object A: You resort to using GEOMETRY.

4 Method of trigonometric parallaxes June p December Foreground Star Distant Stars

5 Parallax decreases with distance Closer stars have larger parallaxes: Distant stars have smaller parallaxes:

6 Stellar parallaxes All stellar parallaxes are less than 1 arcsecond Nearest Star, α Centauri, has p=0.76-arcsec Cannot measure parallaxes with naked eye. First parallax observed in 1837 (Bessel) for the star 61 Cygni. Use photography or digital imaging today.

7 Parallax formula p = parallax angle in arcseconds d = distance in Parsecs

8 Parallax Second = Parsec (pc) Fundamental unit of distance in Astronomy A star with a parallax of 1 arcsecond has a distance of 1 Parsec. Relation to other units: 1 parsec (pc) is equivalent to 206,265 AU 3.26 Light Years 3.085x10 13 km

9 Light year (ly) Alternative unit of distance 1 Light Year is the distance traveled by light in one year. Relation to other units: 1 light year (ly) is equivalent to 0.31 pc 63,270 AU Used mostly by Star Trek, etc.

10 Examples α Centauri has a parallax of p=0.76 arcsec: A distant star has a parallax of p=0.02 arcsec:

11 Limitations If stars are too far away, the parallax can be too small to measure accurately. The smallest parallax measurable from the ground is about 0.01-arcsec Measure distances out to ~100 pc But, only a few hundred stars this close

12 Hipparcos satellite European Space Agency Launched in 1989 Designed to measure precision parallaxes to about ±0.001 arcseconds! Gets distances good out to 1000 pc Measured parallaxes for ~100,000 stars!

13 Future missions Space Interferometry Mission (SIM) Launch in about 2013 Goal of 4 microarcseconds Direct parallax to any star in our Galaxy Pointed observations of specific targets GAIA European mission; launch in about 2012 Roughly microarcseconds precision Measure every star in the Galaxy over roughly 5 years

14 In-class assignment The smallest angle that can be reliably measured for parallax purposes is about 0.01 second of arc. Suppose there are 0.08 stars/pc 3 observable near the Sun. How many stars, in principle, exist that could have their distances measured by the parallax method? If accuracy improved to second of arc (with Hipparcos, for example), how many stars would have measurable parallaxes?

15 How bright is an object? We must define Brightness quantitatively. Two ways to quantify brightness: Intrinsic Luminosity: Total Energy Output. Apparent Brightness: How bright it looks from a distance.

16 Luminosity Luminosity is the total energy output from an object. Measured in Power Units: Energy/second emitted by the object (e.g., Watts) Independent of Distance Important for understanding the energy production of a star.

17 Apparent brightness Measures how bright an object appears to be to a distant observer. What we measure on earth ( observable ) Measured in Flux Units: Energy/second/area from the source. Depends on the Distance to the object.

18 Inverse Square Law of Brightness The apparent brightness of a source is inversely proportional to the square of its distance: 2-times Closer = 4-times Brighter 2-times Farther = 4-times Fainter

19 d=1 B=1 d=2 B=1/4 d=3 B=1/9

20 Apparent brightness of stars Apparent brightness is what we measure. How bright any given star will appear to us depends upon 2 things: How bright it really is (Luminosity) How far away it is (Distance).

21 Appearances can be deceiving... Does a star look bright because it is intrinsically very luminous? it is intrinsically faint but located nearby? To know for sure you must know: the distance to the star, or some other, distance-independent property of the star that clues you in.

22 Flux-luminosity relationship Relates apparent brightness (Flux) and intrinsic brightness (Luminosity) through the Inverse Square Law of Brightness:

23 Measuring apparent brightness The process of measuring the apparent brightnesses of objects is called Photometry. Two ways to express apparent brightness: as Stellar Magnitudes as Absolute Fluxes (energy per second per area)

24 Magnitude system Traditional system dating to classical times (Hipparchus of Rhodes, c. 300 BC) Rank stars into 1 st, 2 nd, 3 rd, etc. magnitude. 1 st magnitude are brightest stars 2 nd magnitude are the next brightest and so on... Faintest naked-eye stars are 6 th magnitude.

25 Modern system Modern version quantifies magnitudes as: 5 steps of magnitude = factor of 100 in Flux. 10 th mag star is 100 fainter than 5 th mag 20 th mag star is 10,000 fainter than 10 th mag Computationally convenient, but somewhat obtuse.

26 Flux photometry Measure the flux of photons from a star using a light-sensitive detector: Photographic Plate Photoelectric Photometer (photomultiplier tube) Solid State Detector (e.g., photodiode or CCD) Calibrate the detector by observing a set of Standard Stars of known brightness.

27 Measuring luminosity In principle you just combine the brightness (flux) measured via photometry the distance to the star using the inverse-square law. The biggest problem is finding the distance.

28 d=1 B=1 d=2 B=1/4 d=3 B=1/9

29 Summary Distance is important but hard to measure Trigonometric parallaxes direct geometric method only good for the nearest stars (~500pc) Units of distance in Astronomy: Parsec (Parallax second) Light Year

30 Summary Luminosity of a star: total energy output independent of distance Apparent brightness of a star: depends on the distance by the inversesquare law of brightness. measured quantity from photometry.

31 Binary stars Apparent Binaries Chance projection of two distinct stars along the line of sight. Often at very different distances. True Binary Stars: A pair of stars bound by gravity. Orbit each other about their center of mass. Between 20% and 80% of all stars are binaries.

32 Types of binaries Visual Binary: Can see both stars & follow their orbits over time. Spectroscopic Binary: Cannot separate the two stars, but see their orbit motions as Doppler shifts in their spectra. Eclipsing Binary: Cannot separate stars, but see the total brightness drop when they periodically eclipse each other.

33 Visual Binary

34 Center of Mass Two stars orbit about their center of mass: a 2 a 1 M 2 a M 1 Measure semi-major axis, a, from projected orbit and the distance. Relative positions give: M 1 / M 2 = a 2 / a 1

35 Measuring masses Newton s Form of Kepler s Third Law: Measure Period, P, by following the orbit. Measure semi-major axis, a, and mass Ratio (M 1 /M 2 ) from projected orbit.

36 Problems We need to follow the orbits long enough to trace them out in detail. This can take decades. Need to work out the projection on the sky. Everything depends critically on the distance: semi-major axis depends on d derived mass depends on d 3!!

37 Spectroscopic binaries Most binaries are too far away to see both stars separately. But, you can detect their orbital motions by the periodic Doppler shifts of their spectral lines. Determine the orbit period & size from velocities.

38 B A B A B A A B

39 Problems Cannot see the two stars separately: Semi-major axis must be guessed from orbit Can t tell how the orbit is tilted on the sky Everything depends critically on knowing the distance.

40 Eclipsing binaries Two stars orbiting nearly edge-on. See a periodic drop in brightness as one star eclipses the other. Combine with spectra which measure orbital speeds. With the best data, one can find the masses without having to know the distance!

41 Eclipsing binary Brightness 1 2 Time 3 4

42 Problems Eclipsing Binaries are very rare Orbital plane must line up just right Measurement of the eclipse light curves complicated by details: Partial eclipses yield less accurate numbers. Atmospheres of the stars soften edges. Close binaries can be tidally distorted.

43 Stellar masses Masses are known for only ~200 stars. Range: ~0.1 to 50 Solar Masses Stellar masses can only be measured for binary stars.

44 Stellar radii Very difficult to measure because stars are so far away. Methods: Eclipsing binaries (need distance) Interferometry (single stars) Lunar Occultation (single stars) Radii are only measured for about 500 stars

45 Summary Types of binary stars Visual Spectroscopic Eclipsing Only way to measure stellar masses: Only ~150 stars Radii are measured for very few stars.

46 Questions What makes it necessary to launch satellites into space to measure very precise parallax? Would it be easier to measure parallax from Jupiter? From Venus?

47 Questions How much does the apparent brightness of stars we see in the sky vary? Why? Stars have different colors? So is the amount of light at different wavelengths the same? Can we tell the difference between a very luminous star that is far away and an intrinsically low luminosity star that is nearby?

48 Questions What star do we know the mass of very precisely? Why is it so unlikely that binaries are in eclipsing systems? Most binaries are seen as spectroscopic. Why? How can we know the sizes of more stars than masses?

### Lecture 14: Studying the stars. Astronomy 111 Monday October 16, 2017

Lecture 14: Studying the stars Astronomy 111 Monday October 16, 2017 Reminders Homework #7 due Monday I will give a lecture on DES and LIGO tomorrow at 4pm in the Mitchell Institute Studying the stars

### 5. A particular star has an angle of parallax of 0.2 arcsecond. What is the distance to this star? A) 50 pc B) 2 pc C) 5 pc D) 0.

Name: Date: 1. How far away is the nearest star beyond the Sun, in parsecs? A) between 1 and 2 pc B) about 12 pc C) about 4 pc D) between 1/2 and 1 pc 2. Parallax of a nearby star is used to estimate its

### Measuring the Stars. The measurement of distances The family of distance-measurement techniques used by astronomers to chart the universe is called

Measuring the Stars How to measure: Distance Stellar motion Luminosity Temperature Size Evolutionary stage (H-R diagram) Cosmic distances Mass The measurement of distances The family of distance-measurement

### Parallax: Measuring the distance to Stars

Measuring the Stars Parallax: Measuring the distance to Stars Use Earth s orbit as baseline Parallactic angle = 1/2 angular shift Distance from the Sun required for a star to have a parallactic angle of

### Chapter 11 Surveying the Stars

Chapter 11 Surveying the Stars Luminosity Luminosity: Rate of energy emitted by star every second. Apparent brightness (flux): Amount of energy passing through every second per unit area. Luninosity =

### 15.1 Properties of 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 do we measure stellar masses? How do we measure

### Stellar distances and velocities. ASTR320 Wednesday January 24, 2018

Stellar distances and velocities ASTR320 Wednesday January 24, 2018 Special public talk this week: Mike Brown, Pluto Killer Wednesday at 7:30pm in MPHY204 Why are stellar distances important? Distances

### Determining the Properties of the Stars

Determining the Properties of the Stars This set of notes by Nick Strobel covers: The properties of stars--their distances, luminosities, compositions, velocities, masses, radii, and how we determine those

### ASTR-1020: Astronomy II Course Lecture Notes Section III

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

### Basic Properties of the Stars

Basic Properties of the Stars The Sun-centered model of the solar system laid out by Copernicus in De Revolutionibus (1543) made a very specific prediction: that the nearby stars should exhibit parallax

### Chapter 10 Measuring the Stars

Chapter 10 Measuring the Stars Some of the topics included in this chapter Stellar parallax Distance to the stars Stellar motion Luminosity and apparent brightness of stars The magnitude scale Stellar

### Measuring the Properties of Stars (ch. 17) [Material in smaller font on this page will not be present on the exam]

Measuring the Properties of Stars (ch. 17) [Material in smaller font on this page will not be present on the exam] Although we can be certain that other stars are as complex as the Sun, we will try to

### Lecture 16 The Measuring the Stars 3/26/2018

Lecture 16 The Measuring the Stars 3/26/2018 Test 2 Results D C B A Questions that I thought were unfair: 13, 18, 25, 76, 77, 80 Curved from 85 to 79 Measuring stars How far away are they? How bright are

### Structure & Evolution of Stars 1

Structure and Evolution of Stars Lecture 2: Observational Properties Distance measurement Space velocities Apparent magnitudes and colours Absolute magnitudes and luminosities Blackbodies and temperatures

### Stars I. Distance and Magnitude. How Does One Measure Distance? Distances. Stellar Parallax. Distance Equation some examples!

Stars I Distance and Magnitude Chapter 17 Why doesn t comparison work? Distances The nearest star (Alpha Centauri) is 40 trillion kilometers away(4 ly) Distance is one of the most important quantities

### How to Understand Stars Chapter 17 How do stars differ? Is the Sun typical? Location in space. Gaia. How parallax relates to distance

How to Understand Stars Chapter 7 How do stars differ? Is the Sun typical? Image of Orion illustrates: The huge number of stars Colors Interstellar gas Location in space Two dimensions are easy measure

### Distances to Stars. Important as determines actual brightness but hard to measure as stars are so far away

SECTION II: Nature of Stars Astronomers measure properties of Stars Distance Mass Apparent Brightness Surface Temperature Radius Find that some are related Large Mass Large Absolute Brightness We will

### Measuring Radial & Tangential Velocity. Radial velocity measurement. Tangential velocity measurement. Measure the star s Doppler shift

17. The Nature of the Stars Parallax reveals stellar distance Stellar distance reveals luminosity Luminosity reveals total energy production The stellar magnitude scale Surface temperature determines stellar

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

Astronomy 113 Dr. Joseph E. Pesce, Ph.D. The Nature of Stars 8-2 Parallax For nearby stars - measure distances with parallax July 1 AU d p A A A January ³ d = 1/p (arcsec) [pc] ³ 1pc when p=1arcsec; 1pc=206,265AU=3

The Cosmic Distance Ladder (Mário Santos) What is it? A way to calculate distances to objects very far away based on the measured distances to nearby objects: 1. Start with the distance to the Sun (1 AU)

### Guiding Questions. Measuring Stars

Measuring Stars Guiding Questions 1. How far away are the stars? 2. What is meant by a first-magnitude or second magnitude star? 3. Why are some stars red and others blue? 4. What are the stars made of?

### The Family of Stars. Chapter 13. Triangulation. Trigonometric Parallax. Calculating Distance Using Parallax. Calculating Distance Using Parallax

The Family of Stars Chapter 13 Measuring the Properties of Stars 1 Those tiny glints of light in the night sky are in reality huge, dazzling balls of gas, many of which are vastly larger and brighter than

### Properties of Stars. For such huge objects, stars have comparatively simple properties when seen from a long way off

Properties of Stars For such huge objects, stars have comparatively simple properties when seen from a long way off apparent magnitude distance and direction in space luminosity - absolute magnitude temperature

### Measuring Radial & Tangential Velocity. Radial velocity measurement. Tangential velocity measurement. Measure the star s Doppler shift

17. The Nature of the Stars Parallax reveals stellar distance Stellar distance reveals luminosity Luminosity reveals total energy production The stellar magnitude scale Surface temperature determines stellar

### Lecture Outlines. Chapter 17. Astronomy Today 8th Edition Chaisson/McMillan Pearson Education, Inc.

Lecture Outlines Chapter 17 Astronomy Today 8th Edition Chaisson/McMillan Chapter 17 Measuring the Stars Units of Chapter 17 17.1 The Solar Neighborhood 17.2 Luminosity and Apparent Brightness 17.3 Stellar

### Chapter 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

### The magnitude system. ASTR320 Wednesday January 30, 2019

The magnitude system ASTR320 Wednesday January 30, 2019 What we measure: apparent brightness How bright a star appears to be in the sky depends on: How bright it actually is Luminosity and its distance

### Intro to Astrophysics

Intro to Astrophysics Dr. Bill Pezzaglia 1 III. Introduction To Astrophysics A. Distances to Stars B. Binary Stars C. HR Diagrams 2 Updated: Nov 2007 A. Stellar Distances 1. Method of Parallax 2. Absolute

### Astronomy. The Nature of Stars

Astronomy A. Dayle Hancock adhancock@wm.edu Small 239 Office hours: MTWR 10-11am The Nature of Stars Distances to stars A Star's brightness and Luminosity A Magnitude scale Color indicates a Star's temperature

### The Hertzprung-Russell Diagram. The Hertzprung-Russell Diagram. Question

Key Concepts: Lecture 21: Measuring the properties of stars (cont.) The Hertzsprung-Russell (HR) Diagram (L versus T) The Hertzprung-Russell Diagram The Stefan-Boltzmann Law: flux emitted by a black body

### HOMEWORK - Chapter 17 The Stars

Astronomy 20 HOMEWORK - Chapter 7 The Stars Use a calculator whenever necessary. For full credit, always show your work and explain how you got your answer in full, complete sentences on a separate sheet

### 301 Physics 1/20/09. The Family of Stars. Chapter 12. Triangulation. Trigonometric Parallax. Course/Syllabus Overview Review of 301 stuff Start Ch.

1/20/09 Course/Syllabus Overview Review of 301 stuff Start Ch. 12 More than just knowing various facts Understand how we arrive at these conclusions 301 Physics Physics Concepts Light Properties of (frequency,wavelength,energy)

### Properties of Stars. N. Sharp (REU/NOAO/AURA/NSF)

Properties of Stars N. Sharp (REU/NOAO/AURA/NSF) What properties of the stars can we determine just from this image? Measuring Stars Measuring Stars Information you can get from 1 image: Position on the

### CASE STUDY FOR USE WITH SECTION B

GCE A level 325/0-A PHYSICS PH5 Assessment Unit CASE STUDY FOR USE WITH SECTION B Pre-Release Material To be opened on receipt A new copy of this Case Study will be given out in the examination 325 0A00

### Pr P ope p rti t es s of o f St S a t rs

Properties of Stars Distances Parallax ( Triangulation ): - observe object from two separate points - use orbit of the Earth (1 AU) - measure angular shift of object - angle depends on distance to object

### Chapter 8: The Family of Stars

Chapter 8: The Family of Stars Motivation We already know how to determine a star s surface temperature chemical composition surface density In this chapter, we will learn how we can determine its distance

### Reading and Announcements. Read Chapters 9.5, 9.6, and 11.4 Quiz #4, Thursday, March 7 Homework #5 due Tuesday, March 19

Reading and Announcements Read Chapters 9.5, 9.6, and 11.4 Quiz #4, Thursday, March 7 Homework #5 due Tuesday, March 19 Stars The stars are distant and unobtrusive, but bright and enduring as our fairest

### Chapter 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

### Announcements. Lecture 11 Properties of Stars. App Bright = L / 4!d 2

Announcements Quiz#3 today at the end of 60min lecture. Homework#3 will be handed out on Thursday. Due October 14 (next Thursday) Review of Mid-term exam will be handed out next Tuesday. Mid-term exam

### Lecture 25: The Cosmic Distance Scale Sections 25-1, 26-4 and Box 26-1

Lecture 25: The Cosmic Distance Scale Sections 25-1, 26-4 and Box 26-1 Key Ideas The Distance Problem Geometric Distances Trigonometric Parallaxes Luminosity Distances Standard Candles Spectroscopic Parallaxes

### Today in Astronomy 142: observations of stars

Today in Astronomy 142: observations of stars What do we know about individual stars?! Determination of stellar luminosity from measured flux and distance Magnitudes! Determination of stellar surface temperature

### = 4,462K T eff (B) =

Homework 1 Solutions Problem 1: Star A emits most of its light in the orange, Star B in the gre en and Star C in the blue color range. What wavelengths are these most likely to be, and what effective temperature

### The 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

### Stars: Stars and their Properties

Stars: Stars and their Properties Astronomy 110 Class 10 WHEN I heard the learn d astronomer; When the proofs, the figures, were ranged in columns before me; When I was shown the charts and the diagrams,

### Gaia Launched in Dec D map of the stars near Sun = 10% of Galaxy Measure the positions of a billion stars to brightness V=20 Precise to

Gaia Launched in Dec 2013 3D map of the stars near Sun = 10% of Galaxy Measure the positions of a billion stars to brightness V=20 Precise to 0.000024 arcseconds = hair at 1000km Accurate parallax/distances?

### Review Lecture 15. Luminosity = L, measured in Watts, is the power output(at all wavelengths) of the star,

Review Lecture The Central Problem in astronomy is distance. What we see is basically a twodimensional picture of the sky. To interpret many pieces of information available to the astronomer we need to

### Astronomy 150: Killer Skies. Lecture 20, March 7

Assignments: Astronomy 150: Killer Skies HW6 due next time at start of class Lecture 20, March 7 Office Hours begin after class or by appointment Night Observing continues this week, 7-9 pm last week!

### Astronomical Measurements: Brightness-Luminosity-Distance-Radius- Temperature-Mass. Dr. Ugur GUVEN

Astronomical Measurements: Brightness-Luminosity-Distance-Radius- Temperature-Mass Dr. Ugur GUVEN Space Science Distance Definitions One Astronomical Unit (AU), is the distance from the Sun to the Earth.

### Observed Properties of Stars - 2 ASTR 2120 Sarazin

Observed Properties of Stars - 2 ASTR 2120 Sarazin Properties Location Distance Speed Radial velocity Proper motion Luminosity, Flux Magnitudes Magnitudes Hipparchus 1) Classified stars by brightness,

### Stars: basic observations

Stars: basic observations Basic properties of stars we would like to know in order to compare theory against observations: Stellar mass M Stellar radius R Surface temperature - effective temperature T

### Chapter 8: The Family of Stars

Chapter 8: The Family of Stars We already know how to determine a star s surface temperature chemical composition motion Next, we will learn how we can determine its distance luminosity radius mass Measuring

### Proton-proton cycle 3 steps PHYS 162 1

Proton-proton cycle 3 steps PHYS 162 1 4 Layers of the Sun CORE : center, where fusion occurs RADIATION: energy transfer by radiation CONVECTION: energy transfer by convection PHOTOSPHERE: what we see

How do we know the distance to these stars? The Ping Pong Ball Challenge -Devise a method for determining the height of the ping pong ball above the floor. -You are restricted to the floor. -You can only

### HW 5 posted. Deadline: * Monday 3.00 PM * -- Tip from the coach: Do it earlier, as practice for mid term (it covers only parts included in exam).

Admin HW 5 posted. Deadline: * Monday 3.00 PM * -- Tip from the coach: Do it earlier, as practice for mid term (it covers only parts included in exam). Lab Wednesday/Thursday -- Spectra http://jonsundqvist.com/phys133/labs.html

### Gaia Launched in Dec D map of the stars near Sun = 10% of Galaxy Measure the positions of a billion stars to brightness V=20 Precise to

Gaia Launched in Dec 2013 3D map of the stars near Sun = 10% of Galaxy Measure the positions of a billion stars to brightness V=20 Precise to 0.000024 arcseconds = hair at 1000km Accurate distance, position,

### Astronomy 122 Outline

Astronomy 122 Outline This Class (Lecture 12): Stars Next Class: The Nature of Stars Homework #5 is posted. Nightlabs have started! Stellar properties Parallax (distance) Colors Spectral Classes Music:

### Measuring Distances. Taking the Measure of the Universe

Measuring Distances Taking the Measure of the Universe The Importance of Distance We talked about how the brightness of a star can be due to 2 effects: distance or luminosity. Without a direct measurement

### Characterizing Stars. Guiding Questions. Parallax. Careful measurements of the parallaxes of stars reveal their distances

Guiding Questions Characterizing Stars 1. How far away are the stars? 2. What evidence do astronomers have that the Sun is a typical star? 3. What is meant by a first-magnitude or second magnitude star?

### Characterizing Stars

Characterizing Stars The stars Every star you see in the sky is a large hot ball of gas like our star the Sun. Each one possibly making up a solar system with planets and debris orbiting around them. Stellar

### Which property of a star would not change if we could observe it from twice as far away? a) Angular size b) Color c) Flux d) Parallax e) Proper Motion

Exam #1 is in class next monday 25 multiple-choice questions 50 minutes Similar to questions asked in class Review sheet to be posted this week. We will have two 1-hour review sessions Friday 5-6pm (with

### The Stars. Background & History The Celestial Sphere: Fixed Stars and the Luminaries

The Stars Background & History The Celestial Sphere: Fixed Stars and the Luminaries The Appearance of Stars on the Sky Brightness and Brightness Variations Atmospheric Effects: Twinkling Variable Stars

### Chapter 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:

### ASTR Look over Chapter 15. Good things to Know. Triangulation

ASTR 1020 Look over Chapter 15 Good things to Know Triangulation Parallax Parsecs Absolute Visual Magnitude Distance Modulus Luminosity Balmer Lines Spectral Classes Hertzsprung-Russell (HR) diagram Main

### Universe. Tenth Edition. The Nature of the Stars. Parallax. CHAPTER 17 The Nature of Stars

Universe Tenth Edition The Nature of the Stars Roger A. Freedman, Robert M. Geller, William J. Kaufmann III CHAPTER 17 The Nature of Stars W. H. Freeman and Company Parallax Careful measurements of the

### Chapter 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

### Assignments for Monday Oct. 22. Read Ch Do Online Exercise 10 ("H-R Diagram" tutorial)

Assignments for Monday Oct. 22 Read Ch. 13 + Do Online Exercise 10 ("H-R Diagram" tutorial) Luminosity passing through each sphere is the same. Area of sphere: 4π(radius) 2 Divide luminosity by area to

### Light. Geometric Optics. Parallax. PHY light - J. Hedberg

Light 1. Geometric Optics 1. Parallax 2. Magnitude Scale 1. Apparent Magnitude 2. Describing Brightness 3. Absolute Magnitude 3. Light as a Wave 1. Double Slit 2. The Poynting Vector 4. Blackbody Radiation

### A Random Walk Through Astrometry

A Random Walk Through Astrometry Astrometry: The Second Oldest Profession George H. Kaplan Astronomical Applications Department Astrometry Department U.S. Naval Observatory Random Topics to be Covered

### Chapter 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?

### Distances to the stars Friedrich Bessel Cygni 10 light years. Just beat Struve and Henderson who measured Vega and α Centauri respectively.

Distances to the stars Friedrich Bessel 1838 61 Cygni 10 light years. Just beat Struve and Henderson who measured Vega and α Centauri respectively. Distances to the stars the technique p < 1arcsecond d

### Stellar Masses: Binary Stars

Stellar Masses: Binary Stars The HR Diagram Again A Diagram for People Q: What is happening here? A: People grow. They are born small, and then grow in height and mass as they age (with a fair bit of individual

### ClassAction: Stellar Properties Module Instructor s Manual

ClassAction: Stellar Properties Module Instructor s Manual Table of Contents Section 1: Warm-up Questions...3 Temperature and Color.....4 Section 2: General Questions.....5 Apparent Magnitude and Brightness....6

### Properties of Stars. 1.1 Brightnesses of Stars

Properties of Stars 1.1 Brightnesses of Stars I m sure you have noticed that some stars are very bright, others less bright, and some are quite dim. There is a true brightness of a star and an apparent

### Midterm Study Guide Astronomy 122

Midterm Study Guide Astronomy 122 Introduction: 1. How is modern Astronomy different from Astrology? 2. What is the speed of light? Is it constant or changing? 3. What is an AU? Light-year? Parsec? Which

### PARALLAX AND PROPER MOTION

PARALLAX AND PROPER MOTION What will you learn in this Lab? We will be introducing you to the idea of parallax and how it can be used to measure the distance to objects not only here on Earth but also

### Masses are much harder than distance, luminosity, or temperature. Binary Stars to the Rescue!! AST 101 Introduction to Astronomy: Stars & Galaxies

Last Two Classes Measuring the Stars AST 101 Introduction to Astronomy: Stars & Galaxies 1. Measuring distances 2. Measuring stellar luminosities 3. Measuring temperatures Next 4. Measuring masses Masses

### Searching for Other Worlds

Searching for Other Worlds Lecture 32 1 In-Class Question What is the Greenhouse effect? a) Optical light from the Sun is reflected into space while infrared light passes through the atmosphere and heats

### Stars. Properties of Stars

Stars Properties of Stars Do all stars appear the same? How are they different? Which one looks the coolest? Hottest? Are they all the same brightness? Do they all look the same size? Luminosity: Amount

### Characterizing Stars

Characterizing Stars 1 Guiding Questions 1. How far away are the stars? 2. What evidence do astronomers have that the Sun is a typical star? 3. What is meant by a first-magnitude or second magnitude star?

### Stars, Galaxies & the Universe Announcements. Stars, Galaxies & the Universe Observing Highlights. Stars, Galaxies & the Universe Lecture Outline

Stars, Galaxies & the Universe Announcements HW#3 due Tuesday (Tomorrow) at 3 pm Lab Observing Trip Tues (9/28) & Thurs (9/30) First Exam next Wed. (9/22) in class - will post review sheet, practice exam

### Hertzsprung-Russel Diagrams and Distance to Stars

Chapter 10 Hertzsprung-Russel Diagrams and Distance to Stars 10.1 Purpose In this lab, we will explore how astronomer classify stars. This classificatin one way that can be used to determine the distance

### The Milky Way, Hubble Law, the expansion of the Universe and Dark Matter Chapter 14 and 15 The Milky Way Galaxy and the two Magellanic Clouds.

The Milky Way, Hubble Law, the expansion of the Universe and Dark Matter Chapter 14 and 15 The Milky Way Galaxy and the two Magellanic Clouds. Image taken from the European Southern Observatory in Chile

### Astr 5465 Feb. 6, 2018 Today s Topics

Astr 5465 Feb. 6, 2018 Today s Topics Stars: Binary Stars Determination of Stellar Properties via Binary Stars Classification of Binary Stars Visual Binaries Both stars visible Only one star visible Spectroscopic

### The principle of geometrical parallax

The principle of geometrical parallax One of the hardest things to do in astronomy is to determine how far away things are. Does the star Vega in Lyra appear exceptionally bright because it s an intrinsically

### Astronomy 1 Fall 2016

Astronomy 1 Fall 2016 Announcement: Tonight s observing session with Stephanie Ho has been CANCELLED. She has rescheduled it for 8-9pm on Thursday Nov. 3 rd. Hopefully the clouds will part by then. Lecture

### Light and Stars ASTR 2110 Sarazin

Light and Stars ASTR 2110 Sarazin Doppler Effect Frequency and wavelength of light changes if source or observer move Doppler Effect v r dr radial velocity dt > 0 moving apart < 0 moving toward Doppler

### Stellar Composition. How do we determine what a star is made of?

Stars Essential Questions What are stars? What is the apparent visual magnitude of a star? How do we locate stars? How are star classified? How has the telescope changed our understanding of stars? What

### Astronomy 421. Lecture 8: Binary stars

Astronomy 421 Lecture 8: Binary stars 1 Key concepts: Binary types How to use binaries to determine stellar parameters The mass-luminosity relation 2 Binary stars So far, we ve looked at the basic physics

### A star is at a distance of 1.3 parsecs, what is its parallax?

Stars Spectral lines from stars Binaries and the masses of stars Classifying stars: HR diagram Luminosity, radius, and temperature Vogt-Russell theorem Main sequence Evolution on the HR diagram A star

### Observed Properties of Stars ASTR 2120 Sarazin

Observed Properties of Stars ASTR 2120 Sarazin Extrinsic Properties Location Motion kinematics Extrinsic Properties Location Use spherical coordinate system centered on Solar System Two angles (θ,φ) Right

### Observations of extrasolar planets

Observations of extrasolar planets 1 Mercury 2 Venus radar image from Magellan (vertical scale exaggerated 10 X) 3 Mars 4 Jupiter 5 Saturn 6 Saturn 7 Uranus and Neptune 8 we need to look out about 10 parsecs

### Astro 1050 Mon. Apr. 3, 2017

Astro 1050 Mon. Apr. 3, 017 Today: Chapter 15, Surveying the Stars Reading in Bennett: For Monday: Ch. 15 Surveying the Stars Reminders: HW CH. 14, 14 due next monday. 1 Chapter 1: Properties of Stars

### Astronomy 100 Spring 2006 Lecture Questions Twelve Weeks Review

Astronomy 100 Spring 2006 Lecture Questions Twelve Weeks Review 16-1 Fusion in the Sun The solar corona has temperatures roughly the same as temperatures in the Sun's core, where nuclear fusion takes place.

### Get ready for quiz # 5! Get out a ½ sheet and Calculator

Get ready for quiz # 5! Get out a ½ sheet and Calculator The above image shows the solar eclipse earlier this month as covered and uncovered by several different solar observatories. The innermost image

### Chapter 13 Other Planetary Systems. The New Science of Distant Worlds

Chapter 13 Other Planetary Systems The New Science of Distant Worlds 13.1 Detecting Extrasolar Planets Our goals for learning Why is it so difficult to detect planets around other stars? How do we detect

### Properties of Stars (continued) Some Properties of Stars. What is brightness?

Properties of Stars (continued) Some Properties of Stars Luminosity Temperature of the star s surface Mass Physical size 2 Chemical makeup 3 What is brightness? Apparent brightness is the energy flux (watts/m

### OPTION E, ASTROPHYSICS TEST REVIEW

IB PHYSICS Name: DEVIL PHYSICS Period: Date: BADDEST CLASS ON CAMPUS OPTION E, ASTROPHYSICS TEST REVIEW S1. This question is about the nature of certain stars on the Hertzsprung-Russell diagram and determining

### Observed Properties of Stars - 2 ASTR 2110 Sarazin

Observed Properties of Stars - 2 ASTR 2110 Sarazin Properties Location Distance Speed Radial velocity Proper motion Luminosity, Flux Magnitudes Magnitudes Stellar Colors Stellar Colors Stellar Colors Stars