motion of the sun (1)

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College of the Desert *

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A003

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Astronomy

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Apr 29, 2024

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docx

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3

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Motion of the Sun Student name: Goal : To study the motion of the Sun and to learn about the zodiacal constellations. The Ecliptic The Sun has two different apparent motions through the sky. Once each day it rises in the eastern part of the sky, crosses the observer’s local Celestial Meridian at midday, then sets in the western part. The average time between two consecutive meridian crossings (transits) of the Sun is defined to be 24 hours and 0 minutes, or one mean solar day. The exact points where the Sun rises and sets vary with the seasons. We’ll study that effect in another project. The Sun’s other apparent motion is slower. The Earth orbits the sun every 365.256 days. As viewed from the Sun, this motion carries Earth eastward relative to the background stars (in the sky, east is the direction of increasing right ascension). From our point of view, the Sun appears to circle the Earth, also moving eastward relative to the background stars. The path of the Sun’s apparent motion on the celestial sphere is called the ecliptic . Since once around the ecliptic equals 360°, the Sun appears to move slightly less than 1° per day (or almost 180° per half year). Thus, stars that happen to be next to the sun in the daytime sky in December, and therefore cannot be seen will be visible at night in June, when the Sun is in the opposite part of the sky! This apparent motion of the Sun relative to the stars also means that stars rise about 4 minutes earlier each night. The ecliptic is divided into 12 constellations called the zodiacal constellations. The Sun passes though these constellations at the approximate rate of one per month, so they are convenient for roughly describing the sun’s location on the celestial sphere. According to astrologers, the position of the Sun and planets among the zodiacal constellations at the time of your birth determined your future. Tracking the sun We want to watch the sun’s motion around the ecliptic over a period of one year. To get started execute the following Click on the GROUND icon in the horizontal menu Set the date to the 1 st day of this semester second month and the time to 22 pm Click on the search icon in the vertical menu and type in the Sun Center the sun using the CENTER icon on the horizontal menu bar Click on the constellation line and labels Record the required information in result 1 in the table below 1
Now increase the time speed by clicking on the fast forward icon in the horizontal menu bar a couple of times until you get to the next month and record the information until you are done with the whole year. Result 1: The Sun’s motion Date Constellation Name Right Ascension Declination Hours of Daylight Planets Near Sun 2-1-2024 Capricorn 21h01m20. 24s - 16*56’59.4 10h34min none 3-1-2024 Aquarius 22h54m08. 65s -7*00’20.7 11h24min Saturn, Mercury 4-1-2024 Pisces 0h47m38.3 8s +5*06’41.5 12h29min none 5-1-2024 Cetus 2h39m22.7 5s +15*31’20. 4 13h27m None 6-1-2024 Taurus 4h42m41.1 1s +22*14’52. 0 14h09m Venus 7-1-2024 Gemini 6h4702.92s +22*59’45. 9 14h15m Venus 8-1-2024 Cancer 8h51m25.1 8s +17*37’45. 3 13h41m None 9-1-2024 Leo 10h46m59. 06s +7*43’53.1 12h45m None 10-1-2024 Virgo 12h34m53. 54s -3*45’55.0 11h43m Mercury 11-1-2024 Libro 14h31m24. 99s - 14*53’57.8 10h42m None 12-1-2024 Scorpius 16h35m47. 65s - 22*01’44.7 9h58m Mercury 1-1-2025 Sagittarius 18h52m33. 97s - 22*53’21.0 9h52m None In which general direction on the celestial sphere (N, S, E, W) does the Sun move relative to the stars? The Sun moves a lot in the North direction. About how many days does it take for the Sun to make one trip around the ecliptic? It took two months for the Sun to make one trip around the ecliptic. 2
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