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The Stars 2

This sheet of questions goes with the packet handed out in class including information from Star-Finding with a Planisphere by Alan M. MacRobert and The Edmund Sky Guide by Terence Dickinson and Sam Brown.

Reading Questions

Answer the following questions based on the handout and your planisphere. Use complete sentences in your answers: some answers will require frequent returns to the text to figure out and you will need to use more than one sentence in some cases.

For an excellent image of the spectra of representative stars for the main types of stars see this page at the Astronomy Picture of the Day. You can search that site for star colors and come up with a number of pages that show the contrasting real colors of stars.

Here are a series of links that will be useful in introducing the material in this lesson:


APOD: 2004 April 18 - Stellar Spectral Types: OBAFGKM
APOD: 2007 August 13 - The Trifid Nebula in Stars and Dust
APOD: 2005 August 30 - Albireo: A Bright and Beautiful Double
APOD: 2004 July 8 - Southern Cross Star Colors
APOD: 2004 April 10 - Facing NGC 6946
APOD: 2003 February 7 - Orion on Film
APOD: January 13, 1999 - Sagittarius Star Cloud
Black body - Wikipedia, the free encyclopedia
A Wikipedia page describing the spectrum of colors produced by a so-called ‘black body’ which is an idealized model for the colors of hot glowing bodies (such as stars).
A site where you can download files to make your own planisphere. This is useful for locating stars and constellations in the sky.
Properties of Stars
A page from which explains how stars’ luminosities vary.
Atlas of the Universe Spectral Types
Information about types of stars with colors, lifetimes, and masses
Atlas of the Universe Hertzsprung-Russel Diagram
A diagram that shows the types of stars in the galaxy and how they evolve over their lifetimes
Black-body Radiation Applet
A Java-applet showing how temperature is related to the color produced by a glowing-hot object.
  1. What colors do stars come in? Astronomers refer to these colors using one-letter codes. What colors and temperatures do these codes correspond to? Make a chart.
  2. The one-letter codes can be listed in a row like this: OBAFGKM. Come up with an original mnemonic to remember the order of these color codes. The standard (and lame) mnemonic is Oh, Be A Fine Girl/Guy, Kiss Me. Surely you can do better than that!
  3. The color-code system is not really as simple as the plain colors of the stars. What does the spectrum of a star have to do with the Spectral Type (as these codes are properly called)?
  4. What is the star magnitude scale?
  5. What is the faintest magnitude you can see without binoculars or a telescope?
  6. In brighly lit areas fewer stars can be seen than in areas that have few street- and house-lights. Why?
  7. What is the limit in star magnitudes for someone in a city?
  8. How much brighter is a first magnitude star (like Spica, magnitude 1) than a fourth magnitude star (like delta Lyra)?

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  1. Some stars vary in brightness. From the text find at least two examples.
  2. Do the stars move in relation to one another? If so, do people live long enough to notice this motion just by looking up into the sky?
  3. You have been learning how to navigate around the sky using degrees. The sky can be thought of as a huge sphere that we look at from the inside. It is convenient to do this because then distances between objects in the sky can be given in degrees. How many degrees of the sky are there between the point that is due North of you through the zenith to the point that is due South of you? How could you find a point that is 45° from the horizon?
  4. What are some convenient “rulers” you can use to make measurements of distances in degrees on the sky? How could you find 1°, 5°, 10°, or 15° in the sky? Draw pictures.
  5. Which of the Connection maps from your text in more useful this time of year (there are two)? Why?
  6. Compare the constellations shown on these maps to the constellations on your planisphere that can be seen at 20:00 (21:00 daylight savings time). Make a list from each source to make this comparison. The one on page 9 is set up for highest accuracy in mid-September around 20:00 (21:00 daylight savings time). These maps show the constellations that the authors of the text think will be easiest to find. What does that tell you about the other constellations on your planisphere?
  7. Look at your two lists from the previous question. Compare how many bright stars (first or second magnitude) there are in the constellations from the star map constellations vs. the other constellations on your planisphere.

Define the following terms in your own words.

  1. Spectral Type:
  1. Stellar Magnitude:
Last updated: Sep 11, 2008        Home