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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 • • • • • • • Solar system Light-year Milky Way galaxy Spiral galaxy Jacobus Kapteyn Interstellar dust Harlow Shapley • • • • Globular star cluster Spherical distribution Constellation Google Earth Questions • • • • • 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 • • • • 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 • • 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. 4. 5. 6. 7. 8. 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 • 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: • • • • motion parallax, similar triangles, arc minutes, arc seconds. Bibliography • • • 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: • • • • • • • • • • 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 • 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 • • • Orbit Axis Stable Questions • • • • • 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 • Materials and Equipment • • • • • • • • • • • • • 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 • • 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: • • Longitude and latitude Universal time (UT) • • • • • • Basic facts about the sun (size, temperature, distance) Sunspots Magnetic fields Solar cycle Solar limb darkening Carrington rotations Questions • • • • 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: • • • • • • 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 • • • • 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 • • 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.