ASTR 154 Cal State Northridge The Moons Orbit and Eclipses Lab Report

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uneqybir8991

Science

ASTR 154

Cal State Northridge

ASTR

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Attached is the two lab worksheets that need to be filled out and instructions. thank you in advance!

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The Moon’s Orbit and Eclipses Laboratory 8 Objective: In this laboratory the orbit of the moon will be discussed as well as how to determine if the conditions are right for a solar eclipse or a lunar eclipse to occur. Background: As the Earth orbits the Sun, as seen from the Earth the Sun traces out a path in the sky that is called the Ecliptic. When studying the orbit of the Moon and eclipses it is convenient to define a new coordinate system that is referenced to the plane of the Ecliptic as shown in (figure1). The position of the Sun and Moon in the sky as viewed from Earth is depicted. Ecliptic longitude is measured along the Ecliptic in degrees starting from the position of the Sun on the first day of spring in March. This point is called the First Point of Aries. The Ecliptic longitude of the Sun increases approximately one degree per day as the Sun moves eastward along the Ecliptic. Ecliptic latitude locates an object north or south of the Ecliptic. Figure 1 Eclipses The Moon orbits the Earth in a plane that is inclined to the plane of the Ecliptic at an angle of approximately 5 degrees, as depicted in (figure 1). When the Moon has the same Ecliptic longitude as the Sun it is called a New Moon. When the Moon has an Ecliptic longitude greater than the Sun’s by 180 degrees we call it a Full Moon. It takes approximately 29 ½ days for the Moon to go through all its phases and become a New Moon again. Twice every lunar orbit the Moon crosses the Ecliptic. These two points are known as the Ascending Node and Descending Node. Both the Earth and the Moon cast shadows into space. When the shadow of the Moon falls onto the Earth a Solar Eclipse occurs. When the shadow of the Earth falls onto the Moon a Lunar Eclipse occurs. For a Solar Eclipse to occur, the Moon must cross the Ecliptic within 18.5 degrees of the Sun’s current Ecliptic longitude at New Moon. This region that guarantees an Eclipse is called the Eclipse Limits as shown in (Figure 1). Every six months the Moon crosses the Ecliptic within the Eclipse Limits and an eclipse occurs. An interesting property of eclipses is that nearly identical eclipse occurs every 18 years 11 days and 8 hours. This occurs because the line of nodes rotates in a westward direction taking 18 years to complete a full rotation. In the example discussed later eclipses will occur in Feb and July due to the rotation of the line of nodes. The Moons Orbit When a Satellite orbits the Earth the orbit will be an ellipse (Figure 2). An ellipse has the property that the sum of the distance of the orbiting body from the two foci of the ellipse is a constant. The Earth is located at one foci as shown in figure 2. The point of closest approach is called perigee (Pe), and the point of furthest distance is called apogee (Ap). Eccentricity measures how elongated an orbit is. The higher the eccentricity the more elongated the ellipse. A circle has an eccentricity of zero. The eccentricity can be calculated from the Apogee and Perigee distance of the orbiting body with the following formula (and is a unit-less number); 2 Figure 2 Figure 3 As the Moon orbits the Earth its distance from the Earth changes, and so does its observed angular size. The pictures in Figure 3 were taken with the same telescope with the same magnification on different dates. The change in angular diameter of the Moon is quite obvious. The change in Angular size is directly proportional to the distance of the Moon. If the Moon was twice as close to the Earth it would appear twice as big in the sky. 3 Instructions: To collect the data for the moon’s ecliptic latitude, ecliptic longitude and distance from earth we’re going to use the online resource “World Time Clock”. To obtain the information we need about the moon you can either perform a google search or directly link to the website below. Google Search: The Moon Tonight World Time Clock Direct Website: http://time.unitarium.com/moon/where.html Once you have opened the page, should see an animated picture of the moon as it appears now with the clock and moon changing in real time in a window on the right hand side of the screen. This window is displayed in the figure. First change the time of day to midnight. Use the pull down menus below and set the last three columns to 0, 0, 0. Then change the date to the first day of the month and year assigned. We’ll do an example for June 2019. Set the Date to June 1st 2019. Use the pull down feature on to change the step time to 1 day. The top of your window should look as shown. Now we’ll read the data from the table and record the proper information.    Record the Ecliptic Longitude, rounding to the nearest degree. Record the Ecliptic Latitude, rounding to the nearest tenth of a degree. Record the Moon-Earth distance, rounding to the nearest kilometer. 4 The figure below shows obtaining data for the example: For the month and year assigned, collect data for every odd numbered day up to the 27th of that month. Fill in the table below. Month ______________________ Date Year _________________ Ecliptic Longitude Ecliptic Latitude 1 3 5 7 9 11 13 .15 17 19 21 23 25 27 5 Distance from Moon (km) ECLIPSE SEASONS 1. On the graph paper provided, plot the Ecliptic Longitude and Ecliptic Latitude of the Moon for each day in the table. Draw a smooth curve connecting the points. Start with the leftmost point on your graph, and follow the points in order from left to right ONLY. Your pencil should never move from right to left. Find the nodes of the Moon's orbit (the points where the Moon's path crosses the ecliptic) and note the Ecliptic Longitude of each node. Ecliptic Longitude of nodes: Ascending Node: __________________ Descending Node: ____________________ 2. Now that you have completed your graph, estimate the days on which the Sun will be located at one of the nodes. To do this estimate each month having 30 days and the Sun increasing its ecliptic longitude by one degree each day. So take the ecliptic longitude of the node and divide by 30 noting the remainder. The number is the number of months past March 21 and the remainder is the number of days following. For example, if a node is located at an ecliptic longitude of 135°, we first divide by 30 and get an answer of 4.5, which is 4 with a remainder of 15 (do the division long hand). This means that the Sun will be located at this node 4 months and 15 days after March 21. The four months get us to July 21. Then add 15 days to get the date of August 6. Eclipse season dates corresponding to the Nodes: Ascending Node Date- Descending Node Date- ECCENTRICITY OF THE MOON’S ORBIT: 3. Finally, calculate the eccentricity of the moon’s orbit from your data. Looking down the list of Moon-Earth distances find the largest number and record that as the apogee distance (Ap). Then find the shortest distance and record that as the apogee distance (Pe). Then calculate the eccentricity using the formula. Ap = ____________________ Pe = _______________________ Eccentricity = ____________________ 6 Name: _____________________________________ Date: _____________________ Answer Sheet-Lab 9 1. Ecliptic Longitude of nodes: Ascending Node: __________________ Descending Node: ____________________ 2. Eclipse season dates corresponding to the Nodes: Ascending Node Date- 3. Ap = ____________________ Eccentricity = ____________________ Descending Node Date- Pe = _______________________ Name (sign) ________________________ Date ___________________________
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Explanation & Answer

hello there, am through with the work.reac out to me for edits and clarifications if required.

Running Head: ASTRONOMY LAB

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Astronomy Lab
Institutional Affiliation
Date

ASTRONOMY LAB

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Astronomy Lab

Name: _____________________________________ Date: _____________________
Answer Sheet-Lab 9
1. Ecliptic Longitude of nod...


Anonymous
Awesome! Perfect study aid.

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