Stellar Astronomy Sample Questions for Exam 3

1.         Today, the most precise astronomical observations are done using

a)    an eye placed to the eyepiece of a telescope.

b)    a CCD camera placed at the focal point of a telescope.

c)    a photographic plate placed at the focal point of a telescope.

d)    ordinary photographic film placed at the focal point of a telescope.

2.         A spectrograph is

a)    a device that combines the various colors together into white light.

b)    a device that separates the various intensities of light.

c)    a device that separates light into its’ constituent wavelengths.

d)    a device that filters out unwanted light from the background of a telescopic image.

3.         Radio telescopes are

a)    usually very small so that they can be pointed accurately.

b)    always located in outer space to since radio waves do not penetrate the atmosphere.

c)    can only “see” at night.

d)    are very large because the resolution of radio waves is so poor.

4.         Due to their poor resolution, the best radio observatories

a)    use huge radio dishes several miles across.

b)    use multiple radio dishes linked together in an interferometer.

c)    are orbiting spacecraft which are above Earth’s atmosphere.

5.         The LIGO observatory observes

a)    in microwave wavelengths.

b)    gravity waves.

c)    neutrinos.

d)    visible light from orbit

6.         Many types of astronomy can only be performed in space because

a)    objects in space are closer to the stars and can thus see more.

b)    gravity causes the telescopes to sag and in space the sag is eliminated because of weightlessness.

c)    the earth’s atmosphere blocks many of the wavelengths of the electromagnetic spectrum.

d)    clouds interfere with the observing and there are no clouds in space.

e)    All of the above.

7.         Which of the following statements is false ?

a)    The Hubble Telescope is a 2.4 m reflecting telescope in orbit that sees in wavelengths from near infrared to near ultraviolet.

b)    The Spitzer Space Telescope is a space based telescope that observes infrared wavelengths.

c)    The Chandra telescope is an orbiting X-ray telescope that was launched in the 1999.

d)    The FUSE telescope an orbiting telescope that observe in the gamma ray wavelengths.

Short Answer Questions

1.            Describe the criterion used in selecting observatory sites. Why is it that a few sites like Kitt Peak and Mauna Kea have so many telescopes? What are the qualities of these sites that make them so attractive to astronomers?

2.            Describe one of the major space-based telescopes and the wavelengths it observes in.

3.            Briefly describe a prism spectrometer. Include a diagram.

Chapter 13

1.         The color ratio of a star is

a)    the ratio of the magnitude of the star observed through two different color filters.

b)    the ratio of the color of a star to its surface temperature.

c)    the ratio of the color of a star to its diameter.

d)    the ratio of the color of a star to the amount of interstellar reddening.

e)    None of the above.

2.         The stellar spectra classification scheme classifies according to

a)    the mass of the star.

b)    the surface temperature of the star.

c)    the diameter of the star.

d)    the distance to the star.

e)    None of the above.

3.         The absorption spectral lines of hydrogen are weaker for stars at the lowest surface temperatures because

a)   cooler stars have less hydrogen.

b)   the hydrogen has sunk to a hotter level.

c)    at low temperatures the hydrogen emits light instead of absorbing light so there is no absorption spectrum.

d)   at low temperatures all the hydrogen is in the ground state so no electrons are in the excited states that are responsible for absorption.

e)   None of the above, the coolest stars have the strongest hydrogen absorption spectra.

4.         By spectral class, the hottest to coolest stars are

a)    M, K, G, F, A, B & O

b)    A, B, C, D, E, F & G

c)    A, B, F, G, K, M & O

d)    O, B, A, F, G, K & M

5.         The Hertzsprung-Russell diagram is

a)   a plot of mass versus luminosity of stars.

b)   a plot of luminosity versus temperature of stars.

c)    a plot of luminosity versus distance of stars.

d)   a plot of mass versus temperature of stars.

6.         On an H-R diagram, most stars lie in the region called the

a)    main sequence.

b)    subgiant sequence.

c)    giant sequence.

d)    supergiant sequence.

e)    None of the above.

7.         On an H-R diagram, the stars in the top right corner are

a)    supergiants.

b)    white dwarfs.

c)    main sequence.

d)    red dwarfs.

8.         A binary star system is

a)   a single star with a large planet orbiting it.

b)   two stars of equal mass passing each other in space.

c)    two stars in orbit around a common center of mass.

d)   a star that switches on and off in binary code.

e)   None of the above.

9.         Observing binary star systems is important because

a)    they allow us to accurately determine the distance to stars.

b)    they allow us to accurately measure the luminosity of stars.

c)    they allow us to accurately measure the color index of stars.

d)    they allow us to accurately determine the mass of stars.

e)    None of the above, there is no special reason to observe binary star systems.

10.       An eclipsing binary is one in which

a)    both stars are easily visible to the naked eye.

b)    the individual stars can only be identified by their spectra.

c)    both stars can be resolved in a telescope.

d)    the stars pass directly in front of each other, eclipsing each other.

e)    None of the above.

11.       By studying eclipsing binaries we can determine

a)    the individual spectra of both stars.

b)    the diameters of both of the stars.

c)    the masses of both of the stars.

d)    All of the above.

Short Answer Questions

1.    Sketch an H-R diagram. Assume you are plotting a sample of 100 stars that are a good representation of all stars. Label the location of supergiants, main sequence and white dwarf stars.

2.    Explain why the distance to some stars can be determined by parallax but most stellar distances cannot.

3.    Describe the different properties of main sequence stars that are determined by the mass of the star. Why is mass so important to the characteristics of a star?

4.    Why is it so important to study binary systems? What information can be gained from them that can’t be otherwise?

Chapter 14

1.         The visible light we receive from the sun

a)    comes directly from the energy source at the sun’s core.

b)    is radiated from the solar photosphere.

c)    is generated by solar flares.

d)    is called the solar wind.

e)    None of the above, we don’t receive any light from the sun.

2.         Which of the following statements is false?

a)    The photosphere is composed of granules, each about 1000km across, which are convection areas of rising and falling gas.

b)    The chromosphere is composed of spicules that look like blades of burning grass and are 700km across and up to 7,000km high.

c)    The average temperature of the chromosphere is about 10,000°C.

d)    The temperature in the chromosphere decreases with increasing altitude.

3.         The chromosphere of the sun is

a)    hotter than the photosphere by several thousand degrees.

b)    only visible for a brief instant before and after totality during a solar eclipse.

c)    composed of spicules that look like blades of burning grass.

d)    studied by a Flash Spectrum taken during solar eclipses.

e)    All of the above

4.         The corona of the sun is

a)    cooler than the surface of the sun.

b)    visible during a total solar eclipse and in x-rays.

c)    the layer just below the photosphere of the sun.

d)    a uniform sphere surrounding the sun.

5.         Sunspots occur on the sun

a)   in 11 year cycles.

b)   in the polar latitudes of the sun.

c)    singly with no magnetic polarity.

d)   in areas of extremely weak magnetic fields.

6.         Sunspots are

a)    hotter regions on the surface of the sun.

b)    cooler regions (by as much as 1500 °C) on the surface of the sun.

c)    completely black regions where no light at all is produced.

d)    regions of extremely weak magnetic fields.

7.         A butterfly diagram is

a)    a diagram showing the change in number and latitude of sunspots with time.

b)    a diagram showing the change in the pattern colors on butterfly wings with the sunspot cycle.

c)    a diagram showing the change in color of sunspots during their 11 year cycle.

d)    a diagram showing the change in average life span of sunspots during their 11 year cycle.

e)    None of the above.

8.         Historically, the sunspot cycle has

a)    been absolutely constant over all of recorded history.

b)    changed dramatically almost every few decades.

c)    changed gradually over the centuries with periods of low activity corresponding to “little ice ages” here on Earth.

d)    changed slowly over millennia with no observable influence on Earth’s climate.

9.         A solar flare is

a)    a long lived dark spot that appears on the surface of the sun.

b)    a large looped eruption of material from the area around sunspots that follows the magnetic field lines and is about 10,000°C.

c)    a bright area on the surface of the sun surrounding sunspots.

d)    a violent eruption of material from the area around sunspots that can reach temperatures of 5,000,000°C or higher.

Short Answer Questions

1.            Describe the layers of the sun beginning at the visible surface and moving outward. What are the different layers called, how thick are they and what are their temperatures.

2.            Describe the photosphere of the sun. What does it look like, how thick is it, what is the temperature and how does it change with altitude and what does its spectrum look like.

3.            Describe the chromosphere of the sun. What does it look like, how thick is it, what is the temperature and how does it change with altitude and what does its spectrum look like.

4.            Describe sunspots, what are they, what kind of cycles they occur in, what magnetic fields are associated with them and what their temperature is.

5.            Describe at least two types of solar activity other than sunspots.

6.            Describe how the interior structure of the sun is determined. What observations are made, what information is contained in the observations and how is the information used to determine the structure?