Download Light - Indiana University Astronomy

H205 – Cosmic Origins
Exploration Packet 1: Tools of the Astronomer
Your Name _____________________________
Due March 11, 2009
Other Group Members:
_________________________
_________________________
_________________________
Part 1: Light and Color
Examine the images provided with the red and blue gel filters. Select one image and use a pencil to
sketch how the astronomical object appears through each gel.
Image: _______________________________________________________________
Red Gel
Blue Gel
Describe how the appearance of the image seen through the red gel differs from the image seen
through the blue gel. What features are emphasized with each gel? How would observations at
specific colors of light be used by astronomers?
Part 2: Infrared Images
Old Faithful is the most frequently erupting large geyser in Yellowstone National Park. A geyser is a
hot spring which erupts periodically. These eruptions are caused by the buildup of hot water and
steam trapped by constrictions in the "plumbing system" of a hot spring. When enough pressure
builds up the geyser erupts.
1)
2)
3)
4)
5)
Where are the hottest areas of the Old Faithful geyser?
Can you tell which way the breeze is blowing in the images?
How does the temperature of the steam change with distance from Old Faithful?
Do the infrared images give you information that you cannot get from the visible light images?
Do you have any other observations?
Examine the three pairs of images of Old Faithful.
1. What can you learn from the sequence of visible images?
2. What can you learn from the sequence of infrared images?
3. What can you learn from the comparison of visible and infrared images?
4. What do the different colors in the infrared image represent?
5. What color means the hottest area? ______________________________
6. What color means the colder area? _______________________________
7. The visible light images use “true” color, while the infrared images use “pseudo color.”
Describe the difference between pseudo color and true color. In what circumstances would pseudo
color be useful?
8. How can you use the infrared images and visible light images together to learn about an object?
9. What would astronomers learn from observations of astronomical objects in infrared light,
compared to observations in visible light?
Part 3: The Infrared Camera
Experiment with the objects provided to learn how different materials and temperatures affect the
brightness of objects in the infrared. What materials are transparent and what materials are opaque?
What do you observe about the infrared images of people?
Thought question: How will the images produced by the infrared camera look if the lights are turned
off? Make a prediction!
What is the source of the light that we see as visible light?
What is the source of the light that the infrared camera sees?
Part 4: Estimating Temperature (Chapter 5, pages 168-169)
Wien’s Law:
Wavelength(max) = 2,900,000 / Temperature
Wavelengths are measured in nanometers, and temperatures in degrees Kelvin.
Using the infrared camera or a thermometer, measure the temperatures of materials available in the
room (ice, walls, water, hot water, skin, incandescent light bulb.
Using Wien’s Law, determine the wavelength at which each material emits the most thermal radiation.
Material
Temperature
(K)
Peak Wavelength
(nm)
Ice
Walls
Skin
Hot Water
Light Bulb
The Sun
501 nm
The Sun is the brightest in green light, about 500
nanometers. What is its temperature?
Part 5: Telescopes
1. List three particular advantages of reflecting telescopes over refracting telescopes for astronomical
use.
2. Why are very large telescopes needed for most astronomical study?
3. Sketch the basic optical layout used in a
reflecting telescope.
a) Draw the path of light through the
telescope.
b) Label the primary optical elements:
primary mirror, secondary mirror, focus
4. The “Foundation for Astronomy Research”
has asked your group to evaluate a proposal for
a new telescope. Refer to the diagram on the
screen or to the figure on page 195 of your text it
determining whether the telescope your group
has been asked to review should be
recommended for funding. Circle the letter of the
telescope your group is reviewing, and explain
why it should or should not be funded.
A.
B.
C.
D.
E.
F.
G.
H.
A gamma ray telescope in Antarctica to look for black holes
An optical telescope to look for planets around other stars in the Chilean Andes
An X-ray telescope to look at the Sun, to be located near the North Pole
An infrared telescope to search for supernovae, in orbit around the Earth
A UV telescope at the summit of Mauna Kea in Hawaii to look at distant galaxies
An optical telescope to study binary stars in Pleiades Star Cluster from Earth orbit
A radio telescope on the Mojave Desert to search for signals from E.T.
An infrared telescope in Indiana to study star forming regions
Part 6: Reflection (5 minutes, max) – Write a short statement (6-10 sentences) describing what you
learned from these activities, how they relate to course material, and why these activities might have
been included in the course.