Lab 11

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School

University of Nebraska, Omaha *

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Course

001

Subject

Astronomy

Date

May 2, 2024

Type

pdf

Pages

8

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NAME CLASS Go to web site http://astro.unl.edu. Click on the Nebraska astronomy applet project and then go to NAAP Modules(at top of screen) and pick The Cosmic Distance Ladder. Read the materials and complete the guide below and complete the exercises and complete the document below—the background materials will help you answer the questions—the flash demonstration will help you complete the rest. ON LINE LAB 11 Nebraska Astronomy Applet Project Student Guide to the The Cosmic Distance Ladder — Student Guide Exercises The Cosmic Distance Ladder Module consists of material on seven different distance determination techniques. Four of the techniques have external simulators in addition to the background pages. You are encouraged to work through the material for cach technique before moving on to the next technique. Radar Ranging outer solar system out beyond Pluto. These objects are collectively known as the Kuiper Belt. An amateur astronomer suggests using the radar ranging technique to learn the rotation periods of Kuiper Belt Objects. Do you think that this plan would be successful? Explain why or why not? No, Kuiper Belt objects are too small and far away to get a return signal from radar ranging, much less determine their rotation rates from the Doppler Shift of the returned signal. Scanned with CamScanner
Parallax In addition to astronomical applications, parallax is used for measuring distances in many other disciplines such as surveying. Open the Parallax Explorer where techniques very similar to those used by surveyors arc applied to the problem of finding the distance to a boat out in the middle of a large lake by finding its position on a small. scale drawing of the real world. The simulator consists of a map providing a scaled overhead view of the lake and a road along the bottom edge where our surveyor represented by a red X may be located. The surveyor is equipped with a theodolite (a combination of a small telescope and a large protractor so that the angle of the telescope orientation can be precisely measured) mounted on a tripod that can be moved along the road to establish a baseline. An Observer’s View panel shows the appearance of the boat relative to trees on the far shore through the theodolite. Configure the simulator to preset A which allows us to see the location of the boat on the map. (This is a helpful simplification to help us get started with this technique — normally the main goal of the process is to learn the position of the boat on the scaled map.) Drag the position of the surveyor around and note how the apparent position of the boat relative to background objects changes. Position the surveyor to the far left of the road and click take measurement which causes the surveyor to sight the boat through the theodolite and measure the angle between the line of sight to the boat and the road. Now position the surveyor to the far right of the road and click take measurement again. The distance between these two positions defines the baseline of our observations and the intersection of the two red lines of sight indicates the position of the boat. We now need to make a measurement on our scaled map and convert it back to a distance in the real world. Check show ruler and use this ruler to measure the distance from the baseline to the boat in an arbitrary unit. Then use the map scale factor to calculate the perpendicular distance from the baseline to the boat. Question 2: Enter your perpendicular distance to the boat in map units. __ 7.5 Show your calculation of the distance to the boat in meters in the box below. 7.5 units x 20 meters/unit = 150 meters Configure the simulator to preset B. The parallax explorer now assumes that our surveyor can make angular observations with a typical error of 3°. Due to this error we Scanned with CamScanner
will now describe an area where the boat must be located as the overlap of two cones as opposed to a definite location that was the intersection of two lines. This preset is more realistic in that it does not illustrate the position of the boat on the map. Question 3: Repeat the process of applying triangulation to determine the distance to the boat and then answer the following: What is your best estimate for the | 6.5 units or 130 meters perpendicular distance to the boat? What is the greatest distance to the boat | 7.2 units or 144 meters that is still consistent with your observations? What is the smallest distance to the boat | 58 units or 116 meters that is still consistent with your observations? Configure the simulator to preset C which limits the size of the bascline and has an error of 5° in each angular measurement. Question 4: Repeat the process of applying triangulation to determine the distance to the boat and then explain how accurately you can determine this distance and the factors contributing to that accuracy. Reducing the bascline and increasing the angular measurement error greatly reduces the accuracy of determining distance. The best we can do now is say the boat is at least 3 map units (60 meters) away, but we cannot put an upper limit on its distance. Distance Modulus Question 5: Complete the following table conceming the distance modulus for several objects, Apparent Absolute Distance o Object Magnitude Magnitude Modulus Dl:;:r)\cc m M m-M NAAP — Cosmic Distance Ladder 3/8 Scanned with CamScanner
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