Practice Question Answers

Chapter 1: The Size of the Universe

1. Simply multiply! 150 million x 20 = 3000 million or 3,000,000,000 miles away.

2. A trillion  is expressed as 1012, and 100 is 102. So 100 trillion is 1014.

3. Set up this proportion:
Earth Actual        =         Earth Scale
Jupiter Actual                 Jupiter Scale

12,800 km        =        4 cm
143,000 km                     x

x = 44.7 cm (a beach ball)

4. The method here is similar to #3 - use a proportion!
SS Actual        =         SS Scale
MW Actual                 MW Scale

       1 ly                =        1 cm
100,000 ly                         x

x = 100,000 cm = 1000 meters (a domed stadium)


Chapter 2: What does the spectrum tell us?

1. a. Continuous Spectrum - a rainbow of all the colors with no gaps.
    b. Emission spectrum - bright lines separated by blackness
    c. Absorption spectrum - a continuous spectrum with black lines superimposed on top.

2. Every time an electron jumps to a higher energy level it absorbs energy. When it falls back down, it emits a specific wavelength of energy (a photon). This is seen as a line in an emission spectrum.

3. The conversion between Celsius and Kelvin is K = C + 273. So –25 °C  is 248 °K.

4. Wien's Law tells us that the wavelength is 2,900,000/ 248° = 11,694 nm or 11.7 micrometers, which is in the infrared.

5. Again you use Wien's Law:  T = 2,900,000/wavelength  = 2,900,000 / 425 = 6824 °K.  
This star is a little brighter and hotter than the Sun.

6. A blue shift means it is moving toward us, and the red shift means movement away from
us. This indicates a rotation of this galaxy, counterclockwise from our perspective.

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