ASTRONOMY Chapter 11 Sections 0-6

 

Introduction 11-0

  1. What point is the author making by telling the story of the Ephemera?
  2. We live tens of years but stars live billions of years! Clearly, we do not live nearly long enough to witness a single star going through all of its stages of ‘life’, yet astronomers have a very good idea of all the stages of ‘life’ a star passes through. How is this possible?
  3. How does the term “stellar evolution” differ from the term “biological evolution”

 

PART I: Parallax Measurements

11-1: Distances to nearby stars are determined by stellar parallax

  1. On a human scale what is a far distance?
  2. On an astronomical scale what is a far distance?
  3. The sun is the nearest star to us; how far away is the sun; what is this distance in astronomical units? What is the next nearest star to us?  How far away is this star?
  4. Define: Stellar parallax.
  5. What is the basis for our personal parallax vision? What is the basis for astronomical parallax vision?
  6. Using parallax as a means of determining distance, how far can we measure distances using earth bound telescopes?
  7. Using space based telescopes haw far can we measure distances using parallax?
  8. Define: parsec. How long is a parsec in light years?
  9. If astronomers combine the distance is star is from us with the brightness of that star what information can be attained? What value is this information?

 

PART II Magnitude Scales

  1. Two Greek astronomers classified stars by their brightness; name these two important astronomically important people and indicate when they lived.
  2. What assumption did the two astronomers, and their contemporaries, from the previous question make about the relative distances of the stars from earth?
  3. Consider the assumption from the previous question. This is not in the book! Give some thought to why these people made the assumption they did. Jot down some of the things you have thought about.

 

11-2: Apparent Magnitude measures the brightness of stars as seen from earth

  1. What is meant by the term “apparent magnitude”, how is this term abbreviated?
  2. What number is given to the star with the brightest apparent magnitude? What number is given to the next brightest star?
  3. What is the magnitude of the stars that we can barely see?
  4. What does it mean if the apparent magnitude of a star is a negative number?
  5. Which is brighter: a star of m = 1.0 or a star of m = 0.0? Explain how you know.
  6. How is it possible to see a star of m = 30?

 

11-3: Absolute magnitudes and luminosities do not depend on distance

  1. What is meant by the term “absolute magnitude”, how is this term abbreviated?
  2. What variable does the absolute magnitude scale take away regarding the stars the number refers to?
  3. Suppose there are these two stars that are exactly alike but one star appears 9 times dimmer than the other star. How much farther away is the furtherer star than the closer star?
  4. Describe how an astronomer might ascribe an apparent magnitude number to a star; describe how an astronomer would ascribe an absolute magnitude number to a star.
  5. What is the range of ‘M’ values for stars?
  6. What is meant by a star’s luminosity? What is the luminosity of our sun?
  7. Which star has greater luminosity: a star with M = -9 or a star with M = +9. Explain how you know.
  8. What is the unit for luminosity and how is this unit abbreviated?

30.  What is the luminosity of a star of M = -10; what is the luminosity of a star of M = +17?

 

PART III: The Temperatures of Stars  

  1. By the early 20th century (the early 1900ds) astronomers had a catalogue of the stars according to their absolute magnitudes and their luminosities. They still did not know what made these stares shine. So, what did these astronomers do?
  2. As a result of what they did, astronomers could build models of what two features of stars?
  3. What fact about the stars is easily overlooked?

 

11-4: A star’s color reveals it surface temperature

  1. What are the most common colors of the stars?
  2. Is it possible for the blackbody curve of objects with two different temperatures to be the same?
  3. Describe how photometry is done.
  4. If a star’s light is bright through an ultraviolet filter and dim through the yellow and red filter, what is the temperature of that star likely to be?
  5. You are a blackbody radiator; at what temperature do you radiate?

 

11-5 A star’s spectrum also reveals its surface temperature

  1. What is stellar spectroscopy and for what is it used?
  2. When astronomers take the spectrum of a stat’s light what two things must they eliminate? What is left once these things are eliminated?
  3. There’s a lot of information here that requires a really good foundation in chemistry; but in the end, what is the advantage of doing a spectral analysis of a star’s light?

 

11-6: Stars are classified by their spectra

  1. In modern astronomy stars are classified by their temperatures. A letter of the alphabet is given to stars of the same temperature. What are these letters in order from the hottest stars to the coolest? What is the mnemonic the help remember these letters and their order?
  2. What is the temperature range of ‘O’ type stars: what is the temperature range of the ‘M’ class stars?
  3. Between the letters of the alphabetical classification numbers can be assigned. So, which is hotter: a B0 star or a B8 star? Explain how you know.
  4. What is the classification of our sun? (Are we a F5 or a K6 or what?)