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Astronomy
Finding the Center of the Milky Way Galaxy
Using Globular Star Clusters
(from http://www.sciencebuddies.com)
Objective
The objective of this astronomy science fair project is to use Internet-based software
tools and databases to locate the center of the galaxy, based on the distribution of
globular clusters.
Introduction
Our solar system is located nearly 25,000 light-years from the center of our Milky
Way galaxy. We now know that we live in a spiral galaxy, consisting of billions of stars,
and that our galaxy is just one of hundreds of billions of galaxies in the universe.
However, the location of our Sun in the Milky Way, the size of our galaxy, the number
of stars in it, and its structure were all unknown just 100 years ago. During the early
20th century, astronomers were trying to answer these questions using a variety of
techniques. You will use one such method to determine the location of the center of our
galaxy.
The most direct approach, adopted by Jacobus Kapteyn in order to determine the
structure of the Milky Way, inferred distances for a number of stars in various
directions to create a 3-dimensional view of our galaxy. Kapteyn found that our Sun lies
at the very center of a nearly spherical distribution of stars, and he incorrectly
concluded that we lie at the center of the galaxy. What Kapteyn was unaware of was
that our galaxy is filled with starlight-absorbing dust, or interstellar dust. This means
that stars far away from our Sun appear dimmer or are not even visible from Earth.
This effect means we preferentially see the stars nearest to our Sun and cannot easily
observe the other side of the galaxy. Therefore, this is not a good technique to use in
determining the structure of the Milky Way.
Instead, you will adopt a method, used by Harlow Shapley, that correctly infers the
direction of the center of our galaxy. Throughout most of the galaxy, stars are
separated by a few light-years. However, globular star clusters contain anywhere from
10,000 to 1 million stars, densely packed into a region only a few tens to a few hundred
light-years wide. Figure 1 shows a nearby galaxy surrounded by globular clusters.
Because globular clusters contain so many stars, they are much brighter than individual
stars and can be seen in the Milky Way, even at very far distances. Unlike stars, which
tend to rotate around the Milky Way Galaxy in a flattened disk, globular clusters are
distributed in a roughly spherical distribution around the center of the Galaxy. Thus, if
we look toward the center of the Galaxy, we should see more globular clusters than if
we look in the opposite direction.
Figure 1. The famous Sombrero galaxy (M104) is a nearby bright
spiral galaxy. The prominent dust lane and halo of stars and
globular clusters (globular clusters are the bright white spots)
give this galaxy its name. (Wikipedia, 2009.)
In this science fair project, using a compiled list of the Milky Way's globular clusters
(approximately 150), you will count the number of clusters found in each constellation.
Constellations, like the Big Dipper or Orion, serve as a way to orient ourselves and
define directions in our galaxy. You will determine which top three constellations contain
the most globular clusters, and therefore, in which direction most Milky Way globular
clusters exist. Using Google Earth in sky mode, you will determine a best-guess location
for the center of the galaxy and compare this to the correct location.
Terms, Concepts and Questions to Start Background Research
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Solar system
Light-year
Milky Way galaxy
Spiral galaxy
Jacobus Kapteyn
Interstellar dust
Harlow Shapley
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Globular star cluster
Spherical distribution
Constellation
Google Earth
Questions
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What is a globular star cluster?
Why are clusters better than individual stars for creating a 3-dimensional view of
our galaxy?
How are globular clusters distributed around galaxies?
How big is the Milky Way?
What is a constellation?
Bibliography
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Fromert, H. (2008). Milky Way Globular Clusters by Name. Retrieved January 12,
2009, from http://seds.org/~spider/spider/mwgc/Add/gc_nam.html
Google. (2009). Google Earth. Retrieved January 12, 2009, from
http://earth.google.com/
Smith, H.E. The Structure of the Milky Way. Retrieved January 24, 2009, from
the University of California, San Diego, Center for Astrophysics & Space
Sciences website: http://cass.ucsd.edu/public/tutorial/MW.html
Cudworth, K.M. (1999, March 7). Short Essays: Galactic Structure, Globular
Clusters. Retrieved January 24, 2009, from
http://nedwww.ipac.caltech.edu/level5/ESSAYS/Cudworth/cudworth.html
Materials and Equipment
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Personal computer with Internet access and Google Earth installed; see the
Experimental Procedure below for more details
Lab notebook
Experimental Procedure
1. Do your background research so that you are knowledgeable about the terms,
concepts, and questions above.
2. Go to http://seds.org/~spider/Spider/MWGC/Add/gc_nam.html.
a. You should see a table of globular clusters in the Milky Way.
b. Column 1 ("Globular Cluster") contains the name(s) of a particular cluster.
c. Column 2 ("Con") contains the abbreviated name of the constellation where
it is found.
3. Count how many globular clusters are in each constellation, as follows.
a. M2 is the first globular cluster in the list. Click on its name to get more
detailed information.
b. Below the cluster's name at the very top of the page, you should see:
"Globular Cluster M 2 (NGC 7089), class II, in Aquarius." This means that
the globular cluster M2 is seen in the constellation "Aquarius."
c. Make a data table in your lab notebook, add the constellation Aquarius, and
put M2 next to it.
d. Go back to the main globular cluster page, from step 2, and repeat the
process for each globular cluster.
e. Add a new line in your data table for each constellation, but if a cluster is
in a constellation that you already have in your list, put the cluster's name
on that line instead of on a new one.
Example: Aquarius: M2, M72, NGC7492, etc.; Scorpius: M4, Terzan1,
etc.; Etc.
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f. Ignore "Possible Further Candidates" and "Former Candidates" near the
bottom of the main page.
g. Count the number of globular clusters you found in each constellation and
record the numbers in another column in your data table.
Identify the three constellations with the most globular clusters seen in them.
Now go to http://earth.google.com and click "Download Google Earth."
a. Click "Agree and Download."
b. Once the file has been downloaded, install the program.
c. Open the Google Earth program.
Set up Google Earth in Sky Mode.
a. At the top, click "View" and then click "Switch to Sky."
b. On the left-hand side of the window, you should see "Layers."
c. Uncheck every item, except "Imagery" and "Backyard Astronomy."
d. Click the arrow next to "Backyard Astronomy."
e. Uncheck every item except "Constellations."
Try to become familiar with the Google Earth navigation controls by panning
around and zooming in and out, using the controls located in the top right corner
of the screen.
Notice the bright band that stretches across the sky. This is the disk of our
Milky Way galaxy!
9. Find the three constellations that contain the most globular clusters, which you
identified in step 4.
a. On the left-hand side is a search bar; type in the name of the first
constellation.
b. Repeat for the other two constellations.
c. Zoom out and pan the sky until you can see all three constellations at once.
10. Are the three constellations near each other? Most of the Milky Way's globular
clusters should be in the direction of the center of the galaxy. Where do you
think the center of the galaxy is?
11. In the search bar, type "Galactic Center" to find the true center of the galaxy.
How close was your guess?
Variations
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Find the distribution of globular clusters in the Milky Way by plotting their
locations using Google Earth.
Similar Triangles: Using Parallax to Measure
Distance
(from http://www.sciencebuddies.com)
Objective
The goal of this project is to measure the distance to some distant, small objects using
motion parallax.
Introduction
Try this: hold a pencil straight in front of you at arm's length. Close one eye and line the
pencil up with a distant object (e.g., a light switch on the wall across the room). Now,
without moving the pencil, close the other eye and look at the pencil. The pencil appears
to move—it is no longer aligned with the distant object. What happened?
Because of the distance between your two eyes, each eye views the pencil from a
slightly different angle (labeled P in Figure 1, below). By alternately viewing the pencil
with each eye alone, you are changing your point of view by the distance that separates
your eyes. Each eye alone will see the pencil aligned at a different position on a distant
background. Thus, when you close one eye and then the other, the pencil appears to
move relative to the background.
Figure 1. If you view an object held at arm's length first through one eye and then
through the other, the object appears to move relative to a more distant background.
This is an example of motion parallax.
What you are seeing with the pencil is an example of motion parallax, the apparent
motion of an object against a distant background due to motion of the observer.
Astronomers can use motion parallax to measure the distance to stars that are
relatively close to earth. With the distances involved, the trick of simply closing one eye
and then the other doesn't work for stars. You need a much bigger distance between
the two observations than the distance between your eyes. Astronomers take advantage
of the earth's travel in its orbit around the sun to obtain the maximum separation
between two observations of a star (see Figure 2, below). The parallax angle, P, is
measured by comparing the nearby star's position to the stable position of distant
background stars.
Figure 2. Astronomers can use motion parallax to measure the distance to nearby stars.
They take advantage of the earth's travel in its orbit around the sun to obtain the
maximum distance between two measurements. The star is observed twice, from the
same point on earth and at the same time of day, but six months apart. (Wikipedia,
2006b)
Terry Herter, a professor of astronomy at Cornell University, has written a cool
interactive Java applet that illustrates how astronomers use motion parallax to measure
distances to nearby stars (Herter, 2006). You can click and drag on the star in the
applet to change its distance from earth. When you do, you will see how its apparent
motion for an observer on earth changes with its distance from earth.
How is the distance from earth to the star calculated? The method is called
triangulation, because you are using the properties of triangles to measure the distance.
In this case it is a right triangle, with the sun forming the vertex of the right angle.
The length of the short side of the triangle (distance from the earth to the sun) is
known. The parallax angle is measured from observations of the nearby stars motion
relative to distant background stars. Astronomers can make this measurement using
photographs taken with the telescope. They can measure the angle of the nearby star's
motion because they have previously calibrated the angle subtended by the field of view
of the telescope.
The motion is measured in angular units called arc seconds. (One degree of arc can be
divided into 60 arc minutes, and each minute of arc can be divided into 60 arc seconds.
So an arc second is 1/3600th of a degree.) The parallax angle, p is equal to one half of
the observed motion, measured in arc seconds (see Figure 2).
Here is the equation used for calculating the distance to a nearby star (you can read
how this equation was derived in the Wikipedia article on parallax (Wikipedia
contributors, 2006a)):
The parallax angle, p, is given in arc seconds.
You can use a similar technique to measure the distance of objects that you observe
with a telescope. For astronomers, the background objects against which nearby stars
are measured is essentially at infinity. The angular motion is measured by calibrating the
angle of view of the telescope, and making measurements from photographs. You'll make
your measurements with a known distance from the object to a calibration grid behind
the object. You'll use the parallax angle and similar triangles to figure out the distance
between the object and the telescope. The Experimental Procedure section shows how
you can do this on a football field.
Terms, Concepts and Questions to Start Background Research
To do this project, you should do research that enables you to understand the following
terms and concepts:
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motion parallax,
similar triangles,
arc minutes,
arc seconds.
Bibliography
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This webpage has an interactive animation that shows how astronomers use stellar
parallax to measure how far a star is from Earth. You can click and drag to change
the distance of the star from Earth, and see how the star's movement changes
compared to distant background objects. (Requires Java.):
http://www.astro.ubc.ca/~scharein/a311/Sim/new-parallax/Parallax.html.
Wikipedia has an excellent article on motion parallax. Pay special attention to the
section on "Parallax and measurement instruments." You'll need to know this
material when carrying out your measurements for this project!
Wikipedia contributors, 2006a. "Parallax," Wikipedia, The Free Encyclopedia
[accessed December 5, 2006]
http://en.wikipedia.org/w/index.php?title=Parallax&oldid=90766442.
Wikipedia also has a good explanation of arc minutes:
Wikipedia contributors, 2006b. "Minute of Arc," Wikipedia, The Free
Encyclopedia [accessed December 5, 2006]
http://en.wikipedia.org/w/index.php?title=Minute_of_arc&oldid=91111438.
Materials and Equipment
To do this experiment you will need the following materials and equipment:
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telescope,
long tape measure,
easel,
background grid with regular spacing (e.g., graph paper),
penny, washer, pencil, or similar small object,
support from which to hang the small object (tripod, music stand, etc.),
string,
pencil,
lab notebook,
empty football field.
Experimental Procedure
1. At one end of the field, set up the easel with the grid attached to it so that it is
perpendicular to the ground. Position the grid at a convenient height for viewing
straight-on with the telescope. Hang two small objects directly in front of the
center of the grid at two different distances (d') from the easel. Measure and
record the distance, d', for each object.
2.
Figure 3. Diagram showing the similar triangles used to calculate the distance, d,
from the telescope to the object. Note that the distance, d', from the object to
the grid has been exaggerated to make the labeling clear.
3. Set up your telescope approximately 100 meters away from the easel, so that it is
directly in front of the grid. The objects should line up with the center of the
grid when centered in the telescope. Mark the center line of the grid, and mark
the position of the telescope.
4. Now move the telescope one meter to the left, keeping it at the same height.
Center the first object in the telescope, and use the grid to measure how far the
object is from the center line (this is your b' measurement for the first object).
Then center the second object in the telescope, and use the grid to measure how
far the object is from the center line (this is your b' measurement for the
second object).
5. Now move the telescope one meter to the right of the straight-on position. Again,
center each object and measure how far it is from the center line.
6. Average your left and right measurements for each object to get b'.
7. Use the ratio s'/b' = s/b to calculate the distance s from the telescope to
each object.
8. Is the distance between the two objects the same as what you get from your
direct measurements?
9. Use a tape measure to measure the distance from the telescope (center position)
to the objects. How does the direct measurement compare to your parallax
calculations?
Variations
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What is the smallest angle you can reliably resolve at 100 meters with a 2-meter
baseline? Explain how this relates to the maximum distance you can measure with
this set-up.
The Reason for the Seasons
(from http://www.sciencebuddies.com)
Objective
To investigate how axial tilt affects how the Sun's rays strike Earth and create
seasons.
Introduction
Where most people live on Earth, summers are hot and filled with many hours of strong
sunlight, while winters are cold due to shortened hours of daylight and weak sunlight.
You might think that the extreme heat of summer and the icy cold of winter have
something to do with how close Earth is to the Sun, but actually, Earth's orbit is almost
circular around the Sun, so there is very little difference in the distance from Earth to
the Sun throughout the year. So, what are the reasons for the seasons, if it's not the
distance from the Sun? One big part of the answer is that Earth is tilted on an axis.
What is an axis? Picture an imaginary stick going through the north and south poles of
Earth. Earth rotates about this axis every 24 hours. However, this axis isn't straight up
and down as Earth goes through its orbit about the Sun. Instead, it is tilted
approximately 23 degrees. The degree of tilt varies by about 1.5 degrees every 41,000
years, which you can read more about in the Bibliography, below. We can thank our
relatively big Moon for keeping this degree of tilt so stable. Without the influence of
our Moon's gravity, the tilt would vary dramatically, like that of a wobbling top,
resulting in rapidly changing seasons that would make it difficult for life to exist on
Earth. Planetary scientists think that our relatively big Moon, and the axis tilt itself,
were created by enormous collisions Earth experienced early in its formation 4.5 billion
years ago.
How does the tilt of the axis create seasons? The tilt changes how the sunlight hits
Earth at a given location. As shown in Figure 1, Earth's axis (the red line) remains fixed
in space. It always points in the same direction, as Earth goes through its orbit around
the Sun.
Figure 1. This drawing shows how Earth's axis remains fixed in
space (pointing in the same direction) as Earth goes through its
orbit around the Sun.
When it is summer in North America, the top part of the axis (the north pole) points in
the direction of the Sun, and the Sun's rays shine directly on North America; while in
South America, the axis is tipped away from the Sun and the Sun's rays hit Earth on a
slant. So, when it is summer in North America, it is winter in South America. When it is
winter in North America, the north pole is tipped away from the Sun, and the Sun's rays
hit the Earth on a slant there; meaning it is summer in South America, because the
Sun's rays hit Earth more directly in that hemisphere. As for the intermediate seasons,
spring and fall, these are seasons when neither the top, nor the bottom, of Earth's axis
are pointed in the direction of the Sun, days and nights are of equal length, and both
the top half and the bottom half of Earth get equal amounts of light.
Slanted rays are weaker rays because they cover a larger area and heat the air and
surface less than direct rays do. You can see this if you shine a flashlight on a large ball.
If you point the flashlight directly at the ball, it makes a bright, circular spot on the
ball; however, if your point the flashlight at the edge of the ball, the light makes a
duller, more oval-looking spot on the ball. The same thing happens with Earth and the
Sun—imagine the ball is Earth and the flashlight is the Sun. In this astronomy science
fair project, you'll investigate how tilting a surface affects how light rays hit that
surface.
Figure 2. This drawing shows the different shapes and brightness produced by rays of
sunlight that hit Earth more directly (in summer), and rays that hit Earth at a slant (in
winter).
Terms, Concepts and Questions to Start Background Research
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Orbit
Axis
Stable
Questions
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How does Earth's tilt create seasons?
What is a significant feature of the Moon?
Why is the Moon important to life on Earth?
What are the seasons like in the southern hemisphere, as compared to seasons in
the northern hemisphere?
Why do slanted rays from the Sun feel weaker than direct rays from the Sun?
Bibliography
This source describes the formation of the Moon from Earth:
Lovett, R.A. (2007, December 19). Earth-Asteroid Collision Formed Moon Later
Than Thought. National Geographic News. Retrieved January 7, 2009, from
http://news.nationalgeographic.com/news/2007/12/071219-moon-collision.html
This source describes how our relatively large Moon stabilizes Earth's tilt, thereby
controlling the seasons:
• Wilford, J. N. (1993, March 2). Moon May Save Earth From Chaotic Tilting of
Other Planets. The New York Times, Inc. Retrieved January 7, 2009, from
http://query.nytimes.com/gst/fullpage.html?res=9F0CE4DD163CF931A35750C0A
965958260&sec=&spon=&pagewanted=all
This source describes Earth's tilt and how it creates the seasons:
• BBC. (n.d.). The Seasons. Retrieved January 7, 2009, from
http://www.bbc.co.uk/science/space/solarsystem/earth/solsticescience.shtml
This source provides a plot showing how Earth's tilt has changed over the past 750,000
years:
• Berger, A. and Loutre, M.F. (1991). Graph of the tilt of the Earth's axis.
Retrieved January 9, 2009, from
http://www.museum.state.il.us/exhibits/ice_ages/tilt_graph.html
For help creating graphs, try this website:
• National Center for Education Statistics (n.d.). Create a Graph. Retrieved
January 9, 2009, from http://nces.ed.gov/nceskids/CreateAGraph/default.aspx
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Materials and Equipment
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Stepping stool, brick, or large block of wood
Flashlight
Masking tape
Scotch® tape
Pieces of graph paper (4)
Large, firm book or a cutting board
Ruler
Protractor
Optional: Camera
Optional: Light meter
Helper
Lab notebook
Graph paper
Experimental Procedure
Preparing the Light Source
1. Place the stepping stool, brick, or block of wood on a table, or on the flat, firm
floor.
2. Lay the flashlight on its side on top of the stepping stool, brick, or block, and line
up the edge of the flashlight so it is close to the edge of the stepping stool,
brick, or block. Use masking tape to tape the flashlight down so it can't roll
around.
Preparing the Surface
1. Tape a sheet of graph paper to a firm surface, like a large book or a cutting
board, so that the paper will be stiff enough to tilt, and so that you can draw on
it. Ask your parents if it's okay if you use Scotch tape on the surface you have
chosen.
2. Turn on the flashlight.
3. Put the graph paper vertically in front of the flashlight, as shown in Figure 3.
Move the graph paper closer or farther away from the flashlight, until the light
on the paper forms a medium-sized, sharp circle 2–3 inches in diameter. Have a
helper help you measure the distance from the edge of the graph paper to the
block of wood and write down this starting distance in your lab notebook. You will
keep the graph paper at this starting distance for all testing.
Figure 3. This drawing shows how to set up your flashlight and graph paper
for testing.
Testing the Surface
1. Have a helper hold the graph paper vertically (straight up and down) at the
starting distance in front of the flashlight.
2. Use your pencil to draw around the outline of the light on the graph paper. Draw a
line from the circle and note that the graph paper is at 0 degrees for this outline
(no tilt). An alternative to drawing around the outline is to take a picture of the
graph paper with a camera.
3. Observe the brightness of the light inside this outline and record your
observation in your lab notebook, or (optionally) measure the brightness with a
light meter held at a fixed distance from the graph paper.
4. Place the protractor next to the graph paper, at the spot shown in Figure 3, and
tilt the graph paper 10 degrees (tip the cutting board from the 90-degree mark
to the 100-degree mark).
5. Use your pencil to draw around the outline of the light on the same piece of graph
paper. Again, draw a line from this outline and note the angle for this outline on
the graph paper. An optional alternative to drawing around the outline is to take a
picture of your graph paper with a camera.
6. Observe the brightness of the light inside this outline, and record your
observation in your lab notebook, or (optionally) measure the brightness with a
light meter held at a fixed distance from the graph paper. Compare the
brightness to the previous outline.
7. Repeat steps 4–6 for tilt angles of 20, 30, and 40 degrees.
8. Remove the sheet of graph paper and attach a new one.
9. Repeat steps 1–8 two more times.
Analyzing the Graph Paper
1. If you used a camera instead of drawing around the light outlines, print out your
photographs so you can analyze them.
2. For each sheet of graph paper, count the approximate number of squares inside
each light outline. For partial squares, estimate how much of the square is lit up;
for example, if it looks like one-fourth of the square is lit up, add 0.25; if it looks
like half of the square is lit up, add 0.5; if it looks like three-fourths of the
square is lit up, add 0.75. Enter your counts in a data table, like the one below:
Data Table: Number of Lighted Squares
Degree of Tilt
Graph Paper 1
Graph Paper 2
Graph Paper 3
Average Number of Squares
0
10
20
30
40
3. Calculate the average number of squares inside each outline for each degree of
tilt and enter your calculations in the data table.
4. Plot the degree of tilt on the x-axis and the average number of squares
illuminated on the y-axis. You can make the line graph by hand or use a website
like Create a Graph to make the graph on the computer and print it.
5. How did the numbers of squares inside the outline change as the degree of tilt
increased? How did the brightness change? What degree of tilt produces light
similar to what North America experiences in summer? What degree of tilt
produces light similar to what North America experiences in winter?
Variations
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Investigate the axial tilts and the presence or absence of seasons on other
planets. Can you predict which planets have seasons, based on their axial tilts?
Plot the degree of tilt on the x-axis and the illuminance (in lux), from light meter
readings, on the y-axis.
Using the Solar & Heliospheric Observatory Satellite
(SOHO) to Determine the Rotation of the Sun
(from http://www.sciencebuddies.com)
Objective
The objective of this science project is to use the Solar & Heliospheric Observatory
satellite (SOHO) to determine the rotation of the sun.
Introduction
SOHO launched on December 2,
1995 as a joint effort by the
European Space Agency (ESA) and
the US National Aeronautics and
Space Administration (NASA). In
your reading you will learn about the
basic physics of the sun, and how a
star differs from planets like the
Earth. For example, the Sun has a
north and south pole, just as the
Earth does, and rotates on its axis.
However, unlike Earth, which rotates
at all latitudes every 24 hours, the
Sun rotates at a different speed at
the equator than it does at the poles. This is known as differential rotation. In this
project you would use the images of the sun that SOHO beams to Earth and places on
the Internet every day, along with a spherical grid to track the rotation of sunspots.
You will use the data you collect to determine the rotational speed of the sun at
different distances from the equator.
Terms, Concepts and Questions to Start Background Research
In your background reading, you should research the following terms, concepts, and
questions in addition to any other areas that arouse your curiosity:
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Longitude and latitude
Universal time (UT)
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Basic facts about the sun (size, temperature, distance)
Sunspots
Magnetic fields
Solar cycle
Solar limb darkening
Carrington rotations
Questions
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Why does the sun display differential rotation?
Where in space is the SOHO satellite and how was it launched?
What is the MDI? What is the EIT?
If you know the circumference of the sun, how would you calculate how fast a
feature on the surface at the equator is rotating (in kilometers/hour)?
Bibliography
These are some Web resources to get you started with your research about the Sun
and the SOHO satellite:
• High Altitude Observatory Education Pages:
http://www.hao.ucar.edu/Public/education/education.html
• Our Star the Sun: http://sohowww.nascom.nasa.gov/explore/sun101.html
• Terms, Concepts, and Definitions:
http://sohowww.nascom.nasa.gov/explore/glossary.html
• SOHO Satellite Web Site: http://sohowww.nascom.nasa.gov/
Experimental Procedure
After completing your background research, begin
your investigation.
You can find the latest SOHO images at:
http://sohowww.nascom.nasa.gov/data/latestimages.
html You can click on "Near real-time images" to see
the absolute latest images. Click on 256 x 256, 512 x
512, or 1024 x 1024 under any of the different
images types to see past images from that same
instrument.
Some of the best images for tracking sunspots are
those labeled "MDI Continuum." You can also use the
"EIT" images, but those can sometimes be hard to interpret because they show much
more of the activity on the sun. The different EIT images show the solar atmosphere at
different wavelengths (171, 195, 284, and 304 Angstroms). By looking at both MDI
Continuum and EIT images, you can learn more than by looking at just one.
There are some possible problems in obtaining current data. Sometimes one of the
imagers is shut down for maintenance or other reasons, and sometimes the sun does not
show any sunspots. Either of these problems can disrupt your experiment. Fortunately,
the SOHO site archives past images (as indicated above).
Past MDI data also can be found at: http://sohowww.nascom.nasa.gov/sunspots/# Click
on "List of all available daily images" for past images. These images have the advantage
that the sunspots are numbered for identification. MDI Summary Data for the current
year is also available at: http://mdisas.nascom.nasa.gov/health_mon/gif_mag_index.html
Choose images from the column labeled "Continuum."
Thus, if you need to, you can pick a set of past images to perform your experiment.
Regardless of whether you use current data or past data, make sure that your images
fall on consecutive days. Every image has a "timestamp" to indicate the day it was taken.
When you are ready to begin measuring your images, print out the solar grid found at
Sun_grid.pdf. Note that the grid has 36 divisions. (Remember the sun is spherical: so
there are 18 "wedges" in front and 18 in back. Some longitude lines appear closer
together than others due to perspective, but all are equally spaced. Look at a globe to
help you visualize how this is true.)
By holding the grid over the image up to the light, or by placing it on an overhead
projector, you can mark the location of each sunspot group over a period of time. You
can calculate the speed of rotation as follows:
Speed of rotation in days =
# of days
------------------------------------------------(# of divisions the sunspot moves) / 36 divisions
The "# of days" is the elapsed time between your first and last image for a given
sunspot. Just look at a calendar and mark the date of your first and last image. DON'T
count the first day, DO count the other days including the last one. (If you are missing
an image because of bad weather or other problems, that's OK, but you would still count
the missing day. The sun continued to rotate, you just didn't see it!) For example, if a
sunspot moves 18 divisions (18/36 = 1/2 rotation) in 14 days, the projected time for a
complete rotation would be 14 divided by 1/2, which equals 28 days.
Setup a spreadsheet to collect your data and perform your calculations. The same
spreadsheet will make a nice table for your display board.
Variations
•
What is the speed of sunspots at different latitudes, measured in kilometers per
hour at the surface of the sun? Utilizing your background research, can you
explain what is happening?
Using the Solar & Heliospheric Observatory
(SOHO) Satellite to Measure the Motion of
a Coronal Mass Ejection
(from http://www.sciencebuddies.com)
Objective
The goal of this project is to use image data from the Solar & Heliospheric Observatory
Satellite (SOHO) to measure the motion of a coronal mass ejection.
Introduction
You know that the sun is the ultimate source of energy for most life on earth. Sunlight
warms the atmosphere and supplies the energy that plants use to grow. Did you also
know that the sun sometimes releases huge bursts of electrified gases into space?
These bursts are called coronal mass ejections (or CMEs). When CMEs are directed
towards Earth they can generate auroras, the spectacular atmospheric displays also
known as "northern lights" (see Figure 1, below).
Figure 1. An example of an aurora photographed in northern Wisconsin, November 20,
2001 by Chris VenHaus (used with permission, Copyright Chris VenHaus, 2001).
CMEs can not only put on a spectacular light show, they can also wreak havoc with earthorbiting satellites and sometimes even ground-based electrical systems. To understand
how they can cause such widespread damage, here are some basic facts of solar physics
from a NASA press release to help put things in perspective (NASA, 2003).
"At over 1.4 million kilometers (869,919 miles) wide, the Sun contains 99.86 percent of
the mass of the entire solar system: well over a million Earths could fit inside its bulk.
The total energy radiated by the Sun averages 383 billion trillion kilowatts, the
equivalent of the energy generated by 100 billion tons of TNT exploding each and every
second.
But the energy released by the Sun is not always constant. Close inspection of the Sun's
surface reveals a turbulent tangle of magnetic fields and boiling arc-shaped clouds of
hot plasma dappled by dark, roving sunspots.
Once in a while--exactly when scientists still cannot predict--an event occurs on the
surface of the Sun that releases a tremendous amount of energy in the form of a solar
flare or a coronal mass ejection, an explosive burst of very hot, electrified gases with a
mass that can surpass that of Mount Everest." (NASA, 2003)
To understand where CMEs originate, you should do background research on the
structure of the sun. The layers of the sun are illustrated in Figure 2, below (ESA &
NASA, 2007a).
Figure 2. The layers of the sun (ESA & NASA, 2007a).
CMEs were discovered in the early 1970's, although their existence had been suspected
for a long time before that (Howard, 2006). The Solar and Heliospheric Observatory
(SOHO) satellite, a project of international cooperation between ESA and NASA, has
been observing the sun in unprecedented detail since its launch in 1995.
One of the instrument sets aboard SOHO is the Large Angle and Spectrometric
Coronagraph (LASCO). "A coronagraph is a telescope that is designed to block light
coming from the solar disk, in order to see the extremely faint emission from the region
around the sun, called the corona." (LASCO, date unknown). The LASCO instrument is
actually three separate coronagraphs (called C1, C2, and C3). Each of the coronagraphs
has a different field of view, ranging from 3 to 30 solar radii (one solar radius is about
700,000 km, or 420,000 miles).
•
•
•
The C3 coronagraph images the corona from about 3.5 to 30 solar radii.
The C2 coronagraph images the corona from about 1.5 to 6 solar radii.
The C1 coronagraph operated for only the first two and half years after SOHO
was launched. During that time, it imaged the corona from 1.1 to 3 solar radii.
In this project, you will use data from the C2 and/or C3 coronagraphs to measure the
motion of CMEs as they leave the sun.
Terms, Concepts and Questions to Start Background Research
To do this project, you should do research that enables you to understand the following
terms and concepts:
•
•
•
•
•
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coordinated universal time (UTC),
basic facts about the sun (size, distance from earth, temperature),
solar sunspot cycle,
parts of the sun:
o core,
o radiative zone,
o convective zone,
o chromosphere,
o photosphere,
o corona;
coronagraph,
magnetic fields.
Questions
•
Where in space is the Solar & Heliospheric Observatory (SOHO) satellite?
•
What is the Large Angle and Spectrometric Coronagraph (LASCO) instrument on
SOHO?
Bibliography
•
•
These links from the SOHO site will be helpful:
o ESA & NASA, 2007a. "Our Star the Sun," European Space Agency and
National Aeronautics and Space Administration [accessed January 8, 2007]
http://sohowww.nascom.nasa.gov/classroom/sun101.html.
o ESA & NASA, 2007b. "SOHO Glossary for Middle School," European Space
Agency and National Aeronautics and Space Administration [accessed
January 8, 2007]
http://sohowww.nascom.nasa.gov/classroom/glossary_middle.html.
o ESA & NASA, 2007c. "SOHO Glossary," European Space Agency and
National Aeronautics and Space Administration [accessed January 8, 2007]
http://sohowww.nascom.nasa.gov/classroom/glossary.html.
o ESA & NASA, 2007d. "Solar and Heliospheric Observatory (SOHO)
Homepage," European Space Agency and National Aeronautics and Space
Administration [accessed January 8, 2007]
http://sohowww.nascom.nasa.gov/home.html.
o ESA & NASA, 2007e. "SOHO Pick of the Week: CMEs Movin' Out, January
5, 2007," European Space Agency and NASA (National Aeronautics and
Space Agency) [accessed January 19, 2007]
http://sohowww.nascom.nasa.gov/pickoftheweek/old/05jan2007/.
o ESA & NASA, 2006. "Measuring the Motion of a Coronal Mass Ejection,"
European Space Agency and NASA (National Aeronautics and Space
Agency) [accessed January 8, 2007]
http://sohowww.nascom.nasa.gov/classroom/cme_activity.html.
For more information on coronal mass ejections (and solar physics in general), see
these webpages:
o NASA, 2003. "Solar Superstorm," NASA HQ Press Release [accessed
January 11, 2007]
http://science.nasa.gov/headlines/y2003/23oct_superstorm.htm.
o Hathaway, David H., 2006. "Solar Physics: Coronal Mass Ejections,"
Marshall Space Flight Center, National Aeronautics and Space
Administration [accessed January 8, 2007]
http://solarscience.msfc.nasa.gov/CMEs.shtml.
o Webb, David. P., 1995. "Coronal mass ejections: The key to major
interplanetary and geomagnetic disturbances," Rev. Geophys. (33, Suppl.)
[accessed January 8, 2007] available online at:
http://www.agu.org/revgeophys/webb01/webb01.html.
Boen, B., 2006. "Animation of a Coronal Mass Ejection," Solar-B Mission to
the Sun, National Aeronautics and Space Administration [accessed January
8, 2007] http://www.nasa.gov/mission_pages/solar-b/solar_mm_001.html.
o Howard, R.A., 2006. "A Historical Perspective on Coronal Mass Ejections,"
in Gopalswamy, N., R.A. Mewaldt and J. Torsti (eds.), 2006. Solar Eruptions
and Energetic Particles, Washington, D.C.: American Geophysical Union,
preprint available online (requires Adobe Acrobat Reader) [accessed
January 11, 2007]
http://hesperia.gsfc.nasa.gov/summerschool/lectures/vourlidas/AV_intro2
CMEs/
additional%20material/corona_history.pdf.
For information about the LASCO instruments on SOHO, see:
LASCO, date unknown. "About LASCO," Office of Naval Research, U.S. Navy
[accessed January 11, 2007] http://lascowww.nrl.navy.mil/index.php?p=content/about_lasco.
This CME catalog is generated and maintained at the CDAW Data Center by
NASA and The Catholic University of America in cooperation with the Naval
Research Laboratory. SOHO is a project of international cooperation between
ESA and NASA.
Yashiro, S., and N. Gopalswamy, 2006. "SOHO LASCO CME Catalog," CDAW Data
Center[accessed January 8, 2007] http://cdaw.gsfc.nasa.gov/CME_list/.
For more advanced students, this high school-level physics tutorial has
information on kinematics, the physics of velocity and acceleration:
o Henderson, T., 2004. "1-D Kinematics," The Physics Classroom [accessed
April 18, 2008]
http://www.glenbrook.k12.il.us/gbssci/Phys/Class/1DKin/1DKinTOC.html.
For more spectacular aurora images, see Chris VenHaus's website:
VenHaus, C., 2001. "," venhaus1.com [accessed January 12, 2007]
http://www.venhaus1.com/.
o
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•
•
•
Materials and Equipment
To do this experiment you will need the following materials and equipment:
•
•
•
computer with Internet connection and printer,
ruler,
calculator.
Experimental Procedure
1. Below is a series of five images taken from one of the coronagraphs on LASCO. In
each of the images, the white circle shows the size and location of the Sun. The
black disk is the occulting disk blocking out the disk of the Sun and the inner
corona. The tick marks along the bottom of the image mark off units of the Sun's
diameter. To the right of the disk we can see a CME erupting from the Sun.
6. Select a feature that you can see in all five images, for instance the outermost
extent of the bright structure or the inner edge of the dark loop shape. Measure
the position of your selected feature in each image.
7. Measurements on the screen or on a printout can be converted to kilometers
using the simple ratio:
8. The diameter of the sun = 1.4 × 106 km (1.4 million km).
9. From the position and time data, you can calculate the average velocity of the
feature. Velocity tells you how fast the feature is moving, and is defined as the
rate of change of position. The average velocity, v, between successive time
points can be calculated using the following equation:
10. From the velocity and time data, you can calculate the average acceleration of the
feature. The acceleration tells you how quickly the velocity of the feature is
changing over time. The average acceleration between successive time points can
be calculated using the following equation:
11. For each feature that you measure, record your results in a data table like the
following one:
Universal
Time
Time
Interval
(t2 − t1)
Screen
Position
(sscreen,
cm)
Actual
Position
(sactual,
km)
Average
Velocity
Average
Acceleration
08:05
08:36
09:27
10:25
11:23
12. Select another feature, measure its position in all of the images, and calculate its
velocity and acceleration.
a. Are the velocity and acceleration the same or different from those for the
first feature you selected?
b. Which velocity and acceleration measurements are "right"?
c. Scientists often look at a number of points in different parts of the CME
to get an overall idea of what is happening.
13. Repeat the measurements on image sequences from other CMEs. An online catalog
of CME movies is available (Yashiro, S., and N. Gopalswamy, 2006). The following
brief instructions describe how to obtain and use images from the catalog.
a. Click on a month from the table (see screenshot, below).
b. Scroll through the table of CMEs for the month you chose. Pick a CME that
you would like to study further. Click on the 'C3' link in the right-most
column.
c. This will load an MPEG movie in your browser. You'll need to have an MPEG
plug-in such as QuickTime or Windows Media Player configured for your
browser.
d. Here is a link to the movie we used for the remaining still images in the
project: http://lasco-www.nrl.navy.mil/daily_mpg/2002_12/021201_c3.mpg
(from December 12, 2002, starting at 00:18, ending at 23:42).
e. Play the movie, and identify when the CME occurs. (Note that in some cases
there may be multiple CMEs in a single movie.)
f. Use the controls of your MPEG player to step through the movie frame-byframe.
g. Save a sequence of 5–10 images that show the evolution of a CME. (To save
a single frame, right-click on the image and select 'Save image as...'.) Use
these images to make measurements of feature positions, and then
calculate the average velocity and average acceleration.
h. Note that these images will not have tick marks at the bottom. However,
they do still have the diameter of the sun marked (center white ring),
which you can use to scale your measurements as before.
i. Here is a sample set of seven images from the above-referenced MPEG
movie:
14. Here are some questions to think about when writing up your project. These are
important questions in CME research, so you may not be able to answer all (or any)
of them, but they are interesting questions to consider!
a. Sometimes it can be tough to trace a particular feature. How much error
do you think this introduces into your calculations?
b. How does the size of the CME change with time?
c. What kind of forces do you think might be acting on the CME? How would
these account for your data?
Variations
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•
CMEs can disrupt earth-orbiting satellites, and even electrical grids on earth. If
the SOHO LASCO instrument can detect earth-directed CMEs as they leave the
sun, perhaps the early warning can give scientists and engineers on Earth a chance
to take protective measures. From your average velocity calculations, how quickly
would you predict the material would reach the Earth? (More advanced students
should also include initial acceleration in the calculation.) How does this compare
with actual transit times? (You'll need to do background research to find this
information.)
Do background research to find out how long it takes for the material from a
CME to reach Earth (only a subset of CMEs are directed Earth-ward). How much
variation is there in Sun-to-Earth transit time? Using your measurements of
initial velocity and acceleration, estimate how long it would take the ejected
material to reach Earth? How do your estimates compare with actual times? How
much variation is there in CME velocity and acceleration?
X...A Simple Magnetometer
Introduction
Solar storms can affect the Earth's magnetic field causing small changes in its direction at the
surface which are called 'magnetic storms'. A magnetometer operates like a sensitive compass
and senses these slight changes. The soda bottle magnetometer is a simple device that can be
built for under $5.00 which will let students monitor these changes in the magnetic field that
occur inside the classroom. When magnetic storms occur, you will see the direction that the
magnet points change by several degrees within a few hours, and then return to its normal
orientation pointing towards the magnetic north pole.
Objective
The students will create a magnetometer
to monitor changes in the Earth's
magnetic field for signs of magnetic
storms. Just as students may be asked to
monitor their classroom barometer for
signs of bad weather approaching, this
magnetometer will allow students to
monitor the Earth's environment in
space for signs of bad space weather
Materials
One clean 2 liter soda bottle
2 pounds of sand
2 feet of sewing thread
A 1 inch piece of soda straw
Super glue (be careful!)
2 inch clear packing tape
A meter stick
A 3x5 index card
Teacher Notes:
1) Do not use common ‘refrigerator’ plastic/rubber
magnets because they are not properly polarized.
Use only a true N-S bar magnet.
2) Superglue is useful for mounting the magnet on
the card in a hurry, but be careful not to glue the
card to the table underneath as the glue has a habit
of leaking through the paper if too much is used.
3) In the January 1999 issue of Scientific
American, there is a design for a magnetometer
that uses a torsion wire and laser pointer developed
by amateur scientist Roger Baker. You can visit
the Scientific American pages online to get more
information about these other designs.
A small bar magnet
Get this from the Magnet Source. They offer a
Red Ceramic Bar Magnet with 'N' and 'S'
marked. It is 1.5" long. $0.48 each. Catalog
Number DMCPB. Call 1-800-525-3536 or 1888-293-9190 for ordering and details.
Light Sources:
A mirrored dress sequin, or small craft
mirror.
Alternative light source:
Darice, Inc. 1/2-inch round mirror, item No.
1613-41, $0.99 for 10. Order from Darice Inc
1-800-321-1494. mail: 13000 Darice Parkway,
Park 82, Strongsville, Ohio, 44136-6699.
Available at Crafts Stores under trademark
'Darice Craft Designer'
A laser pointer. You will need a test tube ring
stand and a clamp to hold it securely.
A goose neck high-intensity lamp with a clear
bulb.
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Clean the soda bottle thoroughly and remove labeling.
Slice the bottle 1/3 of the way from the top.
Pierce a small hole in the center of the cap.
Fill the bottom section with sand.
Cut the index card so that it fits inside the bottle (See Figure 1).
Glue the magnet to the center of the top edge of the card.
Glue a 2 cm piece of soda straw to the top of the magnet.
Glue the mirror spot to the front of the magnet.
Thread the thread through the soda straw and tie it into a small triangle with 5 cm sides.
Tie a 10 cm thread to the top of the triangle in #9 and thread it through the hole in the cap.
Put the bottle top and bottom together so that the 'sensor card' is free to swing with the
mirror spot above the seam.
12. Tape the bottle together and glue the thread through the cap in place.
13. Place the bottle on a level surface and point the lamp so that a reflected spot shows on a
nearby wall about 2 meters away. Measure the changes in this spot position to detect
magnetic storm events.
Soda bottle
magnetometer
Reflected light ray
from mirror spot on
card to the wall.
Light ray from laser
pointer to mirror spot
on card.
Laser pointer
mounted on
wooden block
Tips
It is important that when you adjust the location of the sensor card inside the bottle that its edges
do not touch the inside of the bottle. Be sure that the mirror spot is above the seam and the taping
region of this seam, so that it is unobstructed and free to spin around the suspension thread.
The magnetometer must be placed in an undisturbed location of the classroom where you can
also set up the high intensity lamp so that a reflected spot can be cast on a wall within 1 meter of
the center of the bottle. This allows a 1 centimeter change in the light spot position to equal 1/4
degree in angular shift of the magnetic north pole. At half this distance, 1 centimeter will equal
1/2 a degree. Because magnetic storms produce shifts up to 5 or more degrees for some
geographic locations, you will not need to measure angular shifts smaller than 1/4 degrees.
Typically, these magnetic storms last a few hours or less.
To begin a measuring session which could last for several months, note the location of the spot
on the wall by a small pencil mark. Measure the magnetic activity from day to day by measuring
the distance between this reference spot and the current spot whose position you will mark, and
note the date and the time of day. Measure the distance to the reference mark and the new
spot in centimeters. Convert this into degrees of deflection for a 1 meter distance by multiplying
by 1/4 degrees for each centimeter of displacement.
You can check that this magnetometer is working by comparing the card's pointing direction
with an ordinary compass needle, which should point parallel to the magnet in the soda bottle.
You can also note this direction by marking the position of the light spot on the wall.
If you must move the soda bottle, you will have to note a new reference mark for the light spot
and the resume measuring the new deflections from the new reference mark as before.
Most of the time there will be few detectable changes in the spot's location, so you will have to
exercise some patience. However, as we approach sun spot maximum between 1999-2002 there
should be several good storms each month, and perhaps as often as once a week. Large magnetic
storms are accompanied by major aurora displays, so you may want to use your
magnetometer in the day time to predict if you will see a good aurora display after sunset. Note:
Professional photographers use a similar device to get ready for photographing aurora in Alaska
and Canada.
This magnetometer is sensitive enough to detect cars moving on a street outside your room. With
a 1-meter distance between the mirror and the screen, a car moving 30-50 feet away produces a
sudden deviation by up to 2 cm from its reference position. The oscillation frequency of the
magnet on the card is about 4 seconds and after a car passes, the amplitude of the spot motion
will decrease for 5-10 cycles before returning to its rest position. You can even determine the
direction of the car's motion by seeing if the spot initially moves east or west! Also, by moving a
large mass of metal...say 30 lbs of iron nails...at distances of 1 meter to 5 meters from the
magnet, you can measure the amount of deflection you get on the spot, and by plotting this, you
may attempt to recover the 'inverse-cube' law for magnetism. This would be an advanced project
for middle-school students, but they would see that magnetism falls-off with distance, which is
the main point of the plotting exercise.
Setting up to take data:
The following information is a step-by-step guide for setting up the magnetometer at home, and
making and recording the measurements.
1) During each of the participating school periods, ask for a volunteer from each of the groups to
bring the magnetometer home.
2) Have the student pick up the magnetometer after school to minimize damaging the system.
3) Once the magnetometer arrives at home, the student will need to find a room were the
instrument will remain undisturbed for the next three days. The student will have to inspect the
instrument for damage during transport from school, and make the necessary repairs so that the
sensor card hangs freely inside the bottle and does not scrape the inside of the bottle as it moves.
4) Obtain a high-intensity lamp, or a desk lamp with a CLEAR bulb. Do not use a bulb with a
frosted lamp because you will not be able to see a glint off of the mirror with such a bulb. The
glint/spot you are looking for is actually the image of the filament of the lamp.
5) With the magnetometer positioned 1 meter from a wall on a table, position the lamp so that
the center of the bulb shines at a 45-degree angle to the mirror. Search for a glint or spot of light
from the mirror on the wall. Make sure the table is stable and not rickety because any vibration
of the table will make reading the spot location very difficult. You may also have to relocate the
magnetometer several times until you find a convenient location in your house where the spot
falls on a wall 1-meter from the magnetometer.
6) Once again, make certain that the sensor card is free to rotate horizontally inside the bottle
after you have finished this set-up process.
7) On an 8 1/2” x 11” piece of white paper, draw a horizontal line along the center of the long
direction of the paper so that you have a line that divides the paper into two parts 4 1/4” x 11” in
size.
8) With a centimeter ruler, draw tic marks every 1 centimeter on this line starting from the lefthand end of the line. Label the first mark on the left end '0', and then below the line, label the
odd-numbered marks with their centimeter numbers. '0, 1, 3, 5, ...' If you label every tic mark, the
scale will be too cluttered to easily read from a 1-meter distance.
9) With the lamp turned on and properly positioned, find the spot on the wall, and position the
paper with the centimeter scale, horizontally on the wall. Before securing to the wall, make sure
that as the spot moves from side to side on the wall, that it travels along the centimeter scale in a
parallel fashion. It is convenient to have the spot moving in a parallel line offset about 1 inch
above the centimeter scale.
Making the measurements:
1) For three days of recording, you will be able to fit Day 1 and Day 2 on the front side of a
sheet of ruled paper, and Day 3 on the back side. For each day, leave a blank for the date,
followed by 4 columns which you will label from left to right 'Time' 'Position' 'Amplitude'
'Comments'.
2) In the 'Time' column, write down the following times in a vertical list:
5:00 PM
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
10:30
11:00
3) The first reading you will make on the first day will always be '15.0' because that is where
you set-up the scale on the spot in Step 10 in the instructions above. For the subsequent
measurements, you will record the actual spot location on your scale. Do NOT reposition the
spot every day. You just need to do this one time at the start of your 2, 3, 5 ...day measurement
series.
4) When making a measurement, turn on and off the lamp from the wall plug only. This will
avoid accidental vibration or lamp motion if you were to try using the switch on the lamp. You
want to avoid disturbing the lamp, magnetometer and centimeter scale during the three-day
session.
5) If you know, for a fact, that the set up was disturbed, recenter the centimeter scale on the
current spot position at the '15 centimeter' point. Make a note that you did this on the data table
at the appropriate time, you can then resume taking normal data at the next assigned time in the
data table. Warning, do not assume that just because a big change in the readings occurred, that
the instrument was disturbed. You could have detected a magnetic storm!! Only recenter the
scale if you physically saw the instrument disturbed, or someone told you that they accidentally
touched it.
6) It is important that you make your measurements within 5 minutes of the times listed in the
data table. If you are unable to do this for any entry, leave it blank and do not attempt to 'fudge'
or estimate what the value could have been. Chances are very good that another student in the
network will have made the missing' measurement.
7) The spot on the wall will probably be irregular in shape. Make yourself familiar with what
the spot looks like as it moves, and find a portion of the spot that has a good, sharp edge, or
some other easily recognized feature. You can also estimate by eye where the center of the spot
is if the spot has a simple...round..shape. Try to make all of your measurements in a consistent
way each time, and to estimate the spot location to the nearest 0.5 centimeter. Record this
number in Column 2 in your data sheet.
8) You may notice several 'behaviors' of the spot. It will either just sit at one location, or it
may oscillate from side to side. At a 1-meter distance from the magnetometer, if the spot swings
back and forth horizontally by an amount LESS than 0.5 centimeters, consider the spot
'Stationary' and write 'S' in Column 3 after your measurement. If it is obvious that the spot is
oscillating back and forth, write 'O' in Column 3 and in Column 4 write down the range of the
swing in centimeters along the scale. Example, if it moves from 13.0 centimeters to 17.0
centimeters, write the average position of '15.0' centimeters in Column 2, and then write '13.0
- 17.0' in Column 4.
9) The last thing you would want to note in your data log is local weather conditions IF there is
a lightning storm going on. Note the time that the lightning began and ended as a 'Note' on the
data page, but don't write this in the data table itself. You also want to mention if the street
outside your house is busy with traffic or not. An estimate of how often a car passes
would be good to note.
10) When your assigned time is finished, bring the data table and magnetometer back to school.
Sample Data. Case 1.
This data (below) was taken at the Goddard Space Flight Center, in an office, using a
magnetometer with a 1-meter distance to the wall. The times are in Eastern Standard Time. The
second column gives the spot location on the meter stick, in centimeters.
3-15-99
11:05
11:35
13:25
14:00
14:20
15:25
16:00
17:00
17:25
Visit
9.5 s
8.5 s
9.0 s
9.0 s
9.0 s
9.0 s
8.0 s
7.5 s
8.0 s
3-16-99
3-17-99
9:25 8.0 s
10:20 6.5 s
13:20 5.0 s
14:25 4.5 s
15:00 4.5 s
15:20 4.0 s
16:10 4.5 s
16:50 4.5 s
9:45 6.5 s
10:40 6.5 s
11:05 6.0 o
11:40 4.0 s
12:15 4.5 s
13:00 6.0 s
13:30 7.0 s
15:35 1.5 s
16:10 2.5 s
17:00 2.5 s
http://www.sec.noaa.gov/SWN
To see if any storms may be brewing before
you begin taking measurements! Most days
are usually very calm.
The Kp magnetic index plot for this preriod
shows a mildly disturbed magnetosphere. The
magnetometer shows some minor activity.
Note that at this location, the measurements
steadily decline (drift westward) between the
morning and evening measurements. A
possible 24-hour effect.
Sample Data: Case 2. A major geomagnetic storm.
The magnetometer trace, below, was taken during Saturday, July 15 between 6AM and 8PM EDT
when no aurora could be seen in the daytime. Observers in Virginia and New England did report
auroral activity Saturday night, long after the worst of the magnetic storm had passed.
The magnetic activity index (Kp) for the above event was rated at 9.0 so it was one of the typically
2-3 strongest geomagnetic storms seen during any solar cycle. The most common storms have Kp
from 6-8 and will be somewhat less easy to see.
The maximum magnetic deviation of the above storm from Maryland was (from the above plot)
about 1.2 degrees and this swing took less than 15 minutes! A potentially stronger swing around
15:00 - 18:00 UT was, unfortunately, missed.
This is the geomagnetic Kp index plot for
the ‘Bastille Day’ storm. It is significant
because a Kp of 9 was determined for 9
hours straight which is very unusual.
This is a plot of the
deflections recorded using a
5-meter distance between
the
wall
and
the
magnetometer,
in
the
basement of my home in
suburban Maryland.
Note, a 1-meter distance
would have only recorded
changes that were 1/5 what
were seen here.
The biggest change of (13.2
- 11.6) = 1.6 degrees
corresponded to a linear
deflection
of
28.5
centimeters for the spot on
the wall.
With a 1-meter distance,
this would have produced a
5.7 centimeter change. The
most common geomagnetic
storms are much less violent
at geographic latitudes near
400, so patience is an asset.
XI...A Bit of Geometry
How does the distance between the mirror and the wall determine the
sentitivity?
As a supplementary activity in applied geometry, you may want to show that the angular
deflection you will see on the wall will equal TWICE the actual angular deflection of the magnet
and its deviation from magnetic north. Here's how to think about this problem.
First, imagine holding the mirror so that it is parallel to the wall, with the light beam also
'skimming the surface' of the mirror. The point where the glancing beam hits the wall will define
'zero degrees'. Now imagine slowly rotating the mirror so that it is at right angles to the wall.
The beam will be reflected directly back to the light source located at '180 degrees'. So, by
rotating the mirror (magnet) by 90 degrees, the light beam spot on the wall will scan through
180 degrees. At a mirror tilt angle of 45 degrees, the beam will be reflected at a 90 degree angle
and the spot on the wall will be at 90 degrees to the light source. For small deviations about this
point, you can use the 'skinny triangle' approximation to convert the spot displacement in
centimeters to a spot displacement in degrees. From the geometry, the relevant formula is:
deflection in centimeters
Angle in degrees =
57. 307 x
distance in centimeters
BUT the true deflection angle will be 1/2 of this amount because of the discussion above. For
example, if the distance between the mirror and the wall is 1 meter ( 100 centimeters) and you
notice a deflection of 1 centimeter from the spots previous position, then the deflection angle of
the magnetic field is just
1 centimeter
Deflection in degrees = 1/2 x 57.307 x
100 centimeter
or 0.28 degrees. If you prefer using minutes of arc ( there are 60 in a degree) then this equals 60
x 0.28 or 17.2 minutes of arc.
Which Combination of Materials Are Best For Mars
Temperatures?
(from All Science Fair Projects/ http://www.all-science-fairprojects.com/project70_7.html)
Purpose
The purpose of this experiment was to find out which type of fabric combinations could
be used in space suits for astronauts exploring Mars.
Experimental Design
The constants in this study were
* Number of tests of each spacesuit prototype, (3).
* Size of water containers
* Amount of water in containers.
* Time of exposure to warm and cold conditions.
* Type of thermometer
* The temperatures that the combinations were tested in
The manipulated variable was the combination of fabrics used for each prototype.
To evaluate the responding variable I measured the water temperature at the start of
the experiment and at the end. I also used a thermometer outside the prototype to
measure the air temperature. All temperatures were measured in degrees Celsius.
Materials
QUANTITY
ITEM
DESCRIPTION
4
Mercury
Thermometers
(Celsius)
30cmx30cmx37cm
Polyester Lycra
fabric
31.4cmx31.4cmx38.4cm
Camouflage
fabric
30.5cmx30.5cmx37.5cm Fleece fabric
30.8cmx30.8cmx37.8cm Aluminized Mylar
30cmx30cmx37cm
foam fabric
32.5cmx32.5cmx39.5cm
Flannel Backed
Vinyl
32cmx32cmx39cm
Vinyl
31.3cmx31.3cmx38.3cm
Rubber Coated
Nylon
32cmx32cmx39cm
Nylon Cordura
fabric
1 pair
Scissors
1 bottle
Liquid Stitch™
1 spool
Brown Thread
1
Sewing Needle
1
Heating Device
3
Plastic Containers
1
Ice Chest Cooler
10 kilo.
Dry Ice
1,273mL
Water
1 pair
Rubber Gloves
Procedures
1. Cut out fabrics
2. Make three different combinations of fabrics.
3. Once the fabric combinations are complete, glue the fabrics for each combination
together.
4. Sew all edges of prototypes together except for top.
5. Sew Velcro® around lids of prototypes
6. Fill plastic container with water to top (make sure temperature is close to 37* C.)
7. Put thermometer in bottle to get starting temperature.
8. Slide bottle in spacesuit prototypes.
9. Velcro lid to the body of spacesuit.
10. Place heaters around spacesuit prototypes.
11. Measure temperature of outside environment.
12. Wait 1 hour and record temperature.
13. Repeat steps 1-12 for cold environment except: Place spacesuit prototypes in
freezer.
14. Repeat steps 1-12 for cold environment except: Place spacesuit prototypes in cooler
with dry ice.