2 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 temperatures Stellar spectra Spectral classification Stellar sizes The Herzsprung-Russell (HR)diagram The main sequence Spectroscopic parallax Extending the cosmic distance Luminosity class Stellar masses
3 Parallax is the apparent shift of an object relative to some distant background as the observer s point of view changes It is the only direct way to measure distances to stars It makes use Earth s orbit as baseline Parallactic angle = 1/2 angular shift A new unit of distance: Parsec By definition, parsec (pc) is the distance from the Sun to a star that has a parallax of 1 (1 arc second) Parallax Formula: Distance (in pc) = 1/parallax (in arcsec) One parsec = 206,265 AU or ~3.3 light-years
4 As the distance increases to a star, the parallax decreases. Examples: If the measured parallax is 1 arcsec, then the distance of the star is 1 pc. If the measured parallax is 0.5 arcsec, then the distance of the star is 2 pc. Note: 1 parsec = 3.26 light-years.
5 Let s get to know our neighborhood: A plot of the 30 closest stars within 4 parsecs from the Sun. The gridlines are distances in the galactic plane (the plane of the disc of the Milky Way) The Solar Neighborhood
6 The Nearest Stars More examples using the parallax formula The nearest star Proxima Centauri (the faintest star of the triple star system Alpha Centauri) has a parallax of 0.76 arcsec. Therefore, distance = 1 / 0.76 = 1.32 pc (4.29 ly) The next nearest star is Barnard s star, with a parallax of 0.55 Therefore, d = 1 / 0.55 = 1.82 pc (5.93 ly)
7 A plot of the 30 closest stars to the Sun From the ground, we can measure parallactic angles of ~1/30 (0.03 ) arcsec, corresponding to distances out to ~30 pc (96 ly). There are several thousand stars within that distance from the Sun. Using the stellar parallax, the distance to these stars can be determined directly
8 A plot of the 30 closest stars to the Sun From space (Hipparcos satellite), parallax s can be measured down to about 5/1000 arcsec, which corresponds to 200 pc (~660 ly). There are several million stars within that distance.
9 Stellar Proper Motion Parallax is an apparent motion of stars due to Earth orbiting the Sun. But stars do have real space motions. Space motion has two components: 1) line-of-sight or radial motion (measured through Doppler shift of emission/absorption lines) 2) transverse motion (perpendicular to the line of sight) observer star radial motion transverse space motion
10 How to determine the two component of the space motion of a star? Use the Doppler shift to determine the radial component. Observe the shift in wavelengths of the emission or absorption lines. Then apply formula of Doppler shift to determine the radial velocity Use the proper motion to determine the transverse component. First we need to measure the proper motion. Proper motion is measured in arc seconds/year. Then we need to know the distance to the star using parallax so we can determine the transverse component Use trigonometry to calculate the transverse velocity This method works for stars that are nearby so we can measure the proper motion. The total velocity can be calculated using the Pythagorean theorem: Total velocity = [(Radial velocity)² + (Transverse velocity)²]
11 Stellar Proper Motion: Barnard s Star Two pictures, taken 22 years apart ( Taken at the same time of the year so it doesn t show parallax!). Barnard s star is a red dwarf of magnitude +9.5, invisible to the naked eye (limit of naked eye is +6) Barnard s star has a proper motion of 10.3 arcsec/year (it is the star with the largest proper motion) Given d = 1.8 pc, this proper motion corresponds to a transverse velocity of ~90 km/s! Question: What does the proper motion depend on? Answer 1: Space velocity Answer 2: Distance
12 Some important definitions and concepts Luminosity is the amount of radiation leaving a star per unit time. Luminosity is an intrinsic property of a star. It is also referred as the star absolute brightness. It doesn t depend on the distance or motion of the observer respect to the star. Apparent brightness or Flux. When we observe a star we see its apparent brightness, not its luminosity. The apparent brightness (or flux) is the amount of light striking the unit area of some light sensitive device such as the human eye or a CCD
13 Apparent Brightness and the Inverse Square Law: Proportional to 1/d 2 Light spreads out like the distance squared. Through a sphere twice as large, the light energy is spread out over four times the area. (area of sphere = 4d 2 ) The apparent brightness or Flux decreases with distance, it is inversely proportional to the square of the distance. It can be determined by: Flux = Luminosity 4d 2 To know a star s luminosity we must measure its apparent brightness (or flux) and know its distance. Then, Luminosity = Flux *4d 2
14 Luminosity and Apparent Brightness Two stars A and B of different luminosity can appear equality bright to an observer if the brightest star B is more distant than the fainter star A
15 The Magnitude Scale 2 nd century BC, Hipparchus ranked all visible stars Faintest He assigned to the brightest star a magnitude 1, and to the faintest a magnitude 6. Later, astronomer found out that a difference of 5 magnitudes from 1 (brightest) to 6 (faintest) correspond to a change in brightness of 100 To our eyes, a change of one magnitude = a factor of in flux or brightness. The magnitude scale is logarithmic. Each magnitude corresponds to a factor of 100 1/ magnitudes = factor 100 in brightness. The magnitude scale was later extended to negative values for brighter objects and to larger positive values for fainter objects Brightest
16 Equivalence between magnitude and brightness Magnitude Brightness The change of brightness between magnitude 1 and 6 is 2.512^5 = 100 In general, the difference in brightness between two magnitudes is: Difference in brightness = ^n, where n is the difference in magnitude Example: What is the difference in brightness between magnitude -1 and +1? Answer: n=2, difference in brightness = 2.512^2 = x = 6.31
17 Absolute Magnitude is the apparent magnitude of a star as measured from a distance of 10 pc (33 ly). Sun s absolute magnitude = +4.8 It is the magnitude of the Sun if it is placed at a distance of 10 pc. Just slightly brighter than the faintest stars visible to the naked eye (magnitude = +6) in the sky.
18 Enhanced color picture of the sky Notice the color differences among the stars
19 Stellar Temperature: Spectra The spectra shows 7 stars with same chemical composition but different temperatures. Different spectra result from different temperatures. Example: Hydrogen absorption lines are relatively weak in the hottest star because it is mostly ionized. Conversely, hotter temperatures are needed to excite and ionize Helium so these lines are strongest in the hottest star. Molecular absorption lines (TiO) are present in low temperature stars. The low temperatures allow formation of molecules Ti Titanium, TiO titanium oxide
20 Spectral Classification: A classification of stars was started by the Pickering s women, a group of women hired by the director of the Harvard College observatory, including Annie Cannon The stars were classified by the Hydrogen line strength, and started as A, B, C, D, Annie Jump Cannon But after a while they realized that there is a sequence in temperature so they rearranged the letters (some letters were drop from the classification) so that it reflect a sequence in temperature. It became: O, B, A, F, G, K, M, (L) A temperature sequence! Cannon s spectral cassification system officially adopted in 1910.
21 Spectral Classification A mnemonic to remember the correct order: Oh Be A Fine Girl/Guy Kiss Me An alternative mnemonic: Oh Brother, Astronomers Frequently Give Killer Midterms Each letter is divided in 10 smaller subdivisions from 0 to 9. The lower the number, the hotter the star. Example, G0 (hotter) to G9 (cooler). The Sun is classified as a G2 star, the surface temperature is 5800 K
22 Strengths of Lines at Each Spectral Type
23 Stellar Radii Almost all stars are so distant that the image of their discs look so small. Their images appear only as an unresolved point of light even in the largest telescopes. Actually the image shows the Airy disk produced by the star. A small number of stars are big, bright and close enough to determine their sizes directly through geometry. Knowing the angular diameter and the distance to the star, it is possible to use geometry to calculate its size. Diameter/2π x distance = Angular diameter/360
24 Stellar Radii One example in which it is possible to use geometry to determine the radius is the star Betelgeuse in the Orion constellation The star is a red giant located about 640 ly from Earth Betelgeuse size is about 600 time larger than the Sun Its photosphere exceed the size of the orbit of Mars Using the Hubble telescope it is possible to resolve its atmosphere and measure its diameter directly The measured angular size is about arc seconds
25 An indirect way to determine the stars radii Most of the stars are too distant or too small to allow the direct determination of their size. But we can use the radiation laws to make an indirect determination of their size. According to Stefan law, the luminosity of a star is proportional to the fourth power of the surface temperature (T 4 ) The luminosity also depend on its surface area. Larger bodies radiate more energy. Luminosity Surface area * T 4
26 Stellar Radii: An indirect way to measure the radius (Read 10-2 More Precisely, Estimating Stellar Radii ) Stefan s Law F = T 4 Flux (F) is the energy radiated per unit area by a black body at the temperature T Luminosity (L) is the Flux (F) multiplied by the entire spherical surface (A) L = A * F Area of sphere A = 4R 2 (R is the radius of the star) Substituting A in the equation of L L = 4R 2 F Substituting F in the equation of L L = 4R 2 T 4 Expressing in solar units (dividing by the solar L, R and T), the constants disappear: L star = (R star /R sun ) 2 * (T star /T sun ) 4 * L sun
27 The relationship between Luminosity, Radius, and Temperature provides a means to evaluate these properties relative to the Solar values. L L L L sun sun 4 4 R R R R 2 For example, a star has 10 times the Sun s radius but is half as hot. (Since this is relative to the Sun, we will consider that the radius of the Sun is 1 and the temperature of the Sun is 1) How much is the luminosity respect to the Sun? sun 2 sun 2 T T T 4 4 sun T sun 4 L Lsun
28 Determining radii using radiation laws The equation L = 4R 2 T 4 can be expressed in solar units as: L(in solar luminosities) = R 2 (in solar radius) * T 4 (in solar surface temperature) If we need to calculate the radius, we can rearrange the equation : R 2 (in solar radius) = L(in solar luminosities) / T 4 (in solar surface temperature)
29 Understanding Stefan s Law: Radius dependence L star = (R star /R sun ) 2 * (T star /T sun ) 4 * L sun Let s consider a star that has a radius twice the radius of the Sun. What will be the luminosity of that start? (assume that the two stars have the same temperature) If we receive 100 photons from the Sun, we should receive 400 photons from a star twice the diameter of the Sun. The star will look four times brighter than the Sun
30 Understanding Stefan s Law: Temperature dependence L star = (R star /R sun ) 2 * (T star /T sun ) 4 * L sun Let s consider a star with a temperature twice that of the Sun and another star with a temperature one third of the Sun The luminosity of a star that has a temperature twice that of the Sun, must be 16 times larger. The luminosity of a star with a temperature 1/3 of the Sun, must be 1/81 that of the Sun The assumption here is that these stars have the same radius
31 Hertzsprung-Russell (HR) Diagram The HR diagram is a plot of star Luminosity versus Temperature (or spectral class) It also give information about: Radius Mass Lifetime Stage of Evolution The Main Sequence is the diagonal band of stars in the HR diagram Stars reside in the main sequence during the period in which the core burns H Most stars (like the Sun) lie on the main sequence. The Sun will spend most of its life in the main sequence (about 5 billion years) Main sequence
32 From Stefan s law... L = 4R 2 T 4 The HR diagram to the right has L and T on the axes. But we can plot R (The other parameter in the equation) also which will appear as straight lines crossing the diagram Let s use the equation and the HR diagram to learn more about L, R and T More luminous stars at the same T must be bigger! Cooler stars at the same L must be bigger!
33 The HR Diagram: 100 Brightest Stars Most luminous stars, because they are so rare, lie beyond 5 pc. If we know the luminosity, we can determine distance from their Flux (brightness). Flux = Luminosity 4d 2 The technique to determine distances to stars using the radiation laws and HR diagram is called: Spectroscopic Parallax
34 The HR Diagram: Spectroscopic Parallax An example to illustrate how this works: Main Sequence 1) We measure the Flux or apparent brightness of a star Apparent brightness is the rate at which energy from the star reaches a detector 2) From the spectrum of a star, we can determine its temperature or the spectral type. 3) Then using the HR diagram we can determine its luminosity assuming it is located in the Main Sequence 4) Use inverse square law to determine distance. Flux = Luminosity 4d 2
35 The HR Diagram: Luminosity & Spectroscopic Parallax What if the star doesn t happen to lie on the Main Sequence - maybe it is a red giant or white dwarf??? We determine the star s Luminosity Class based on its spectral line widths: Spectral lines get broader when the stellar gas is at higher densities - indicates smaller star. Wavelength A Supergiant star A Giant star A Dwarf star (Main Sequence)
36 The HR Diagram: Luminosity Class Bright Supergiants Supergiants Bright Giants Giants Sub-giants Main-Sequence (Dwarfs)
37 Example of absorption lines for different spectral classes The lines are wider for dwarf (denser) stars of spectral class V and narrower for giant stars of spectral class I. Isn t this getting a little circular? First we said that we derive Luminosities from measured Fluxes and Distances? Now we re saying we know the Luminosities and we use them together with Temperatures to derive Distances.. Let s clarify this!
38 More on Spectroscopic Parallax The answer: Now we made use of additional information obtained from the spectral analysis. The spectral analysis provide information to determine the temperature of the star or the spectral classification (Using the spectrum of the star). To do this, we didn t know or need the distance Next we also made use of the HR diagram. If we know the temperature (or the luminosity class), then we can deduce the luminosity
39 We get distances to nearby planets from radar ranging If we know the distance (and we can measure the orbital period), we apply Kepler s 3 rd law to obtain the distance Earth-Sun (AU) That sets the scale for the whole solar system (1 AU). It allows us to get a value for the AU in km (1AU = 150,000,000 km) Knowing the value of the AU in km, we use the stellar parallax, to find distances to nearby stars. The Distance Ladder Use these nearby stars with known distances, then we measure the Fluxes and determine the Luminosities, to calibrate Luminosity classes in HR diagram. Then knowing spectral class (or T) we determine Luminosity. Next we measure the Flux and get Distance for farther stars (Spectroscopic Parallax).
40 Stellar Masses: Visual Binary Stars Binary star are classified as visual, spectroscopic and eclipsing The example shows Sirius (visual binary), the brightest star in the sky. Sirius A has a companion Sirius B, a very dense object called white dwarf With Newton s modifications to Kepler s laws, the period and size of the orbits yield the sum of the masses. P² = a³ /(m 1 + m 2 ) The relative distance of each star from the center of mass yields the ratio of the masses. m 1 d 1 = m 2 d 2 The ratio and the sum provide each mass individually (Two equations and two unknowns). P, a, d1 and d2 are known (they are measured) Note: For Sirius, the plane of the orbit is not face on, it is inclined 46 degrees from the line of sight. A correction needs to be done first before using the values of size of orbit and distance to the center of mass
41 Stellar Masses: Spectroscopic Binary Stars Many binaries are too far away to be resolved or they orbit around the other star at a short distance, but they can be discovered from periodic spectral line shifts. The shift of the spectral lines is causes by the Doppler effect In this example, only the yellow (brighter) star is visible
42 Stellar Masses: Eclipsing Binary Stars How do we identify eclipsing binaries? We can identify an eclipsing binary by observing the light curve of the star, a plot of the apparent brightness of the star as function of time The occultation of the star in the system must be observed only if we can see the orbital plane edge on. This method also tells us something about the stellar radii (Through the deep of the eclipse).
43 The HR Diagram: Stellar Masses Why is the mass of a star so important? Together with the initial composition, mass defines the entire life cycle and all other properties of the star! The composition of the first stars was H and He. After the interstellar gas was contaminated with heavier elements produced in the interior of the starts, the composition of the mass of those starts incorporated those heavier elements The mass determine: Luminosity Radius Surface Temperature Lifetime Evolutionary phases And how the star will end its life. All is determined by the mass of the star.
44 Example: For stars on the Main Sequence, if we plot the luminosity as function of mass, we find that the luminosity depends of the mass: Luminosity Mass 4 Why the luminosity increases at such high rate? A star with more mass means more gravity more pressure in the core higher core temperatures faster nuclear reaction rates fast production of energy ( Mass 4) higher luminosities! shorter lifetime
45 Lifetime Fuel available / How fast fuel is burned So for a star Stellar lifetime Mass / Luminosity Or, since Luminosity Mass 4 (For main sequence stars) Stellar lifetime Mass / Mass 4 = 1 / Mass 3 How long a star lives is directly related to the mass! Example: The Sun lifetime is estimated to be about 10 billion years. A star with 10 times the mass of the Sun has an estimated lifetime of 10 million years! Do the calculation! Big (Massive) stars live shorter lives, burn their fuel faster.
46 H-R diagram Location of stars of different masses
47 The turn off point of two open star clusters in the H-R diagram showing their different ages The turn off points Stars of higher mass leave the Main Sequence earlier What can we deduce from the HR diagram and the turn off points about the relative age of these two clusters?
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 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
Review Chapter 10 TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false. 1) A parsec is about 3.3 light-years. 1) 2) A parsec is slightly more than 200,000 AU. 2) 3) The nearest
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
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
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
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:
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
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
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
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
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
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
Astronomy A. Dayle Hancock email@example.com 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
hapter 15 Surveying the Stars Properties of Stars istances Luminosities s Radii Masses istance Use radar in Solar System, but stars are so far we use parallax: apparent shift of a nearby object against
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
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
Stars: some basic characteristics Stars! How bright are they? How massive are they? What are the different types? How long do they live? How hot are they? Stellar brightness and luminosity The apparent
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?
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
Stars - spectral types 1901: Led by Annie Jump Cannon, Harvard astronomers looked at the spectra of >200,000 stars. Classified them as A, B, C etc. Cannon rearranged them into OBAFGKM based on how lines
STARS CHAPTER 10.1 the solar neighborhood The distances to the nearest stars can be measured using Parallax => the shift of an object relative to some distant background as the observer s point of view
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
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)
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
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
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
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
Chapter 9: Measuring the Stars About 10 11 (100,000,000,000) stars in a galaxy; also about 10 11 galaxies in the universe Stars have various major characteristics, the majority of which fall into several
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
Astr 2320 Tues. March 7, 2017 Today s Topics Chapter 13: Stars: Binary Stars Determination of Stellar Properties vi Binary Stars Classification of Binary Stars Visual Binaries Both stars visible Only one
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
Family of stars Reminder: the stellar magnitude scale In the 1900 s, the magnitude scale was defined as follows: a difference of 5 in magnitude corresponds to a change of a factor 100 in brightness. Dm
Astronomy 113 Dr. Joseph E. Pesce, Ph.D. The Nature of Stars For nearby stars - measure distances with parallax 1 AU d p 8-2 Parallax A January ³ d = 1/p (arcsec) [pc] ³ 1pc when p=1arcsec; 1pc=206,265AU=3
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?
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 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,
Name Mass-Luminosity and Stellar Lifetimes WS The graph shows the Mass-Luminosity Relationship for main sequence stars. Use it to answer questions 1-3. 1) A star with a mass of 0.5 solar masses would be
Test #2 results Grades posted in UNM Learn D C B A Along with current grade in the class F Clicker Question: If the Earth had no Moon then what would happen to the tides? A: The tides would not be as strong
Astro 101 003 Fall 2012 Lecture 8 T. Howard Measuring the Stars How big are stars? How far away? How luminous? How hot? How old & how much longer to live? Chemical composition? How are they moving? Are
My God, it s full of stars! AST 248 N * The number of stars in the Galaxy N = N * f s f p n h f l f i f c L/T The Galaxy M31, the Andromeda Galaxy 2 million light years from Earth The Shape of the Galaxy
OTHER MOTIONS The position of a nearby star changing over a year gives us parallax Stars can also move on their own Real motion, not just our point of view They are just balls of gas and are moving around
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
1 Observations 11 Parameters - Distance d : measured by triangulation (parallax method), or the amount that the star has dimmed (if it s the same type of star as the Sun ) - Brightness or flux f : energy
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
NAME: 1. Define using complete sentences: Globular Cluster: OPEN CLUSTER PRELAB The first place to look for answers is in the lab script! Open Cluster: Main Sequence: Turnoff point: Answer the following
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
Review Questions for the new topics that will be on the Final Exam Be sure to review the lecture-tutorials and the material we covered on the first three exams. How does speed differ from velocity? Give
Observational Astronomy - Lecture 8 Stars I - Distances, Magnitudes, Spectra, HR Diagram Craig Lage New York University - Department of Physics firstname.lastname@example.org April 7, 2014 1 / 36 JPL Horizons Database.
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
Spectral Classification of Stars Sun Sirius Stellar Classification Spectral Lines H Fe Na H Ca H Spectral Classification of Stars Timeline: 1890s Edward C. Pickering (1846-1919) and Williamina P. Fleming
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
6/28 Based on the reduction of the intensity of the light from a star with distance. It drops off with the inverse square of the distance. Intensity is power per unit area of electromagnetic radiation.
Astronomy Exam 3 - Sun and Stars Study online at quizlet.com/_4zgp6 1. `what are the smallest group of stars in the H-R diagram 2. A star has a parallax of 0.05". what is the distance from the earth? white
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:
Structure and Evolution of Stars Lecture 2: Observational Properties Distance measurement Space velocities Apparent magnitudes and colours Absolute magnitudes and luminosities Blackbodies and temperatures
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
Stellar Spectra ASTR 2110 Sarazin Solar Spectrum Test #1 Monday, October 9, 11-11:50 am Ruffner G006 (classroom) You may not consult the text, your notes, or any other materials or any person Bring pencils,
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
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?
The Life Histories of Stars I Birth and Violent Lives Stellar evolution--first problem for new discipline of astrophysics What is a star? What is it made of? How does it produce and release energy? How
What is the Sun s structure? From inside out, the layers are: Core Radiation Zone Convection Zone Photosphere Chromosphere Corona How does the Sun shine? The Sun has its own energy source Main difference
Temperature, Blackbodies & Basic Spectral Characteristics. Things that have one primary temperature but also exhibit a range of temperatures are known in physics as blackbodies. They radiate energy thermally.
Stars III The Hertzsprung-Russell Diagram Attendance Quiz Are you here today? (a) yes Here! (b) no (c) here is such a 90 s concept Today s Topics (first half) Spectral sequence and spectral types Spectral
CHAPTER 29: STARS BELL RINGER: Where does the energy of the Sun come from? Compare the size of the Sun to the size of Earth. 1 CHAPTER 29.1: THE SUN What are the properties of the Sun? What are the layers
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?
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?
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
Solar System Our Solar System has eight planets. The picture below shows their relative sizes, but NOT their relative distances. A planet orbits the sun, and has gravitationally cleared its orbital area
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
Homework Ch 7, 8, 9 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Our most detailed knowledge of Uranus and Neptune comes from 1) A) the
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
Chapter 6: Basic Properties of Stars Star Names Ancient Arabic, Greek or Latin names By constellation, ecreasing orer of brightness α alpha, β beta, γ gamma... Stellar istances Pre-telescope Observations
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
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
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
1 Lecture 26 The Hertzsprung- Russell Diagram January 13b, 2014 2 Hertzsprung-Russell Diagram Hertzsprung and Russell found a correlation between luminosity and spectral type (temperature) 10000 Hot, bright
Beyond Our Solar System Chapter 24 PROPERTIES OF STARS Distance Measuring a star's distance can be very difficult Stellar parallax Used for measuring distance to a star Apparent shift in a star's position
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