Understanding the Celestial Globe in Physical Science 1421

Physical Science 1421 Celestial Globe Equipment Needed Quantity Celestial Globe Map 1 The purpose of this laboratory activity is to learn the basic terms and abbreviations used in the celestial sphere and its coordinate system. Part 1: Background The celestial globe (see Figure 1 ) is one of the oldest tools in Astronomy. Several thousand years ago humans thought the stars and other celestial bodies were affixed to the inner surface of a great celestial sphere that surrounded the Earth and turned daily carrying the Sun, Moon, planets, and stars around it. Modern humans realize there is no real celestial sphere and that the stars and galaxies are distributed throughout space at various distances. Nevertheless, it is still convenient to imagine that the sky is a sphere of great radius with the Earth a tiny object at the center. The celestial globe is a model of this sphere as it would appear if we were viewing it from within the globe. Figure 1 – Celestial Globe For this lab, we will use the SFA Star Chart to find your answer and the 4 charts are attached at the end of the lab report. The charts provided cover the entire celestial sphere. You will notice that there are regions where the charts overlap. For example, Perseus can be found on both Chart 1 and Chart 2.

North Celestial Pole and South Celestial Pole Notice that the globe is pivoted at the North Celestial Pole “ P n ”, and at the South Celestial Pole “ P s ” (see Figure 2 ). These are points on the sky resulting from the intersection of the Earth’s rotation axis and the Celestial Sphere. These points are the extensions of Earth’s North and South Pole onto the Celestial Sphere. Celestial Equator Halfway between the celestial poles lays the celestial equator- the intersection of the plane of the Earth’s equator and the celestial sphere. Notice that the Sun, the Moon, and the planets are not shown on the globe. Because of their distance from the earth, they do not appear to have fixed positions on the celestial sphere. The Right Ascension (R.A.) is marked along the celestial equator . As the Sun moves eastward along the ecliptic, it eventually crosses the celestial equator as it goes from the southern half of the sky into the northern half. This point of intersection is called the vernal equinox , and the Sun arrives there around March 21, the beginning of spring. The word vernal comes from the Latin word for green, thus “spring-like”, and equinox refers to equal lengths of day and night. The reason the Sun appears to move eastward is because the Earth rotates from West to East. We should remember that the Sun rises in the East and sets in the West no matter where you are on planet Earth. p. 2

Perhaps it is convenient at this point you put the celestial globe in such a form that the North Celestial Pole points straight up, so you can visualize the northern hemisphere, the ecliptic and the southern hemisphere. Ecliptic The apparent path of the Sun, called the Ecliptic (see Figure 2 ), is shown inclined 23.5 o with respect to the Celestial Equator . This inclination is the result of the tilt of the Earth’s axis, and is the cause of our seasons. The Ecliptic might also be thought of as the projection of the plane of the Earth’s orbit onto the Celestial Sphere. Months and days of the year are marked off along the Ecliptic so that you can locate the position of the Sun on any day of the year. On the Celestial Globe, the Ecliptic is easily found by looking at the orange dots, which represent the path of the Sun. The ecliptic contains the months of the year and is divided in intervals of 10 o starting from 0 o at the equinox until 360 o the same equinox. The month is represented in roman numerals with the day of the month in standard numbers. Figure 2 - The Plane on the Celestial Globe Declination (Dec.) The angular distance of an object above or below the Celestial Equator is called its Declination (Dec.). If the object is above or north of the Celestial Equator , the declination is positive; if below or south of the Celestial Equator , the declination is negative. Therefore an object on the Celestial Equator has a declination of 0 o ; the North Celestial Pole has a declination of +90 o ; the South Celestial Pole has a declination of -90 o . Parallels/Circles of declinations varying in 10 o are shown on your globe. Declination is NOT latitude dependent; it is a universal-independent coordinate that you can use anywhere in the universe (on the moon, on a space shuttle, etc). Right Ascension (R.A.) Right Ascension (R.A.) of an object is measured eastward from the Spring Equinox (moving parallel to the Celestial Equator ) . Right Ascension is usually measured in hours, minutes, and seconds rather than degrees. In the hours/minutes/seconds measurement of angles a full circle is divided into 24 h (twenty-four hours) rather than 360 degrees; each hour is then divided into 60 m (sixty minutes); and each minute in turn is divided into 60 s (sixty seconds). The Right Ascensions are printed on the p. 3 Vernal Equinox

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Celestial Equator of the globe every hour (they start at 0 h at the Spring Equinox and continue until 24 h at the Spring Equinox again). Note that in this system of angle measurement 1 h = 360 o /24 = 15 o . Part 2: Lab Activity I. 2.1 Big Dipper (in Ursa Major) 1. Locate the Big Dipper (hint: it is in the constellation of Ursa Major , close to the North Celestial P ole ). I pointed an arrow to it in Northern Region chart. 2. Draw in the space provided in the lab report section (as best as you can), the Big Dipper , indicating the position and the name of each star belonging to it. II. Declination (Dec.) Indicate the Declination (Dec.) and Right Ascension (R.A.) of the objects listed in the lab report section. III. Problems Solve the problems in using the celestial globe map. Record your results in the Lab Report section. p. 4

Name: Ana Garcia, Maria Cantu, Alexis Morin, KG Sukati Class: PSCI Lab Date: April 24, 2023 Part 3: Lab Report – Celestial Globe List three things that can be seen in a celestial globe map? 1. Aries 2. Cancer 3. Crux I. Big Dipper Draw in the space provided (as best as you can) the Big Dipper , indicating the position and the name of each star belonging to it (note that the Big Dipper is part of the constellation Ursa Major ). Names of the Stars that Form the Big Dipper 1.- Alkaid 3.- Alioth 5.- Phecda 7.- Dubhe 2.- Mizar 4.- Megrez 6.- Merak 8.- Alcor II. Declination (Dec.) and Right Ascension (R.A.) Indicate the Declination or Right Ascension of the following objects: These tables shouldn’t come side by side since they get disappeared when students upload their reports. Object Declination Constellation Andromeda +40  Constellation Draco +65  Star Beta (β) in Columba -35  Star Diphda in Cetus -17  Star Schedar in Cassiopeia +56  Constellation Corvus - 20  p. 5

Star Markab in Pegasus + 15  Constellation Southern Cross (Crux ) -60  Star Deneb in Cygnus + 45  Star Antares in Scorpius -26  Object Right Ascension (R.A.) Star Sirius in Canis Majoris ( Canis Major ) 6 h 44 m Star Algenib in Pisces 7h Star Gemma in Corona Borealis 15h 34m 41s Star Hamal in Aries 02h 07m 10.40s Star Antares in Scorpius 16h 29m 24.46s Star Vega in Lyra 18h 36m 56s III. PROBLEMS 1. What stars have the following coordinates? R.A. 20 h 40 m , Dec. +45 0 Deneb Star R.A. 22 h 56 m , Dec. -29 o Fomalhaut Star R.A. 04 h 34 m , Dec. +16 o Aldebaran Star or Alpha Tauri 2. Find the Right Ascension (R.A.) and Declination (Dec.) of Arcturus (in α Bootes ) R.A. 14h 15m Dec. +19  3. Estimate the Right Ascension (R.A.) and Declination (Dec.) of the Large Magellanic Cloud near the South Celestial Pole . R.A. = 05h 23m 34s Dec. = 69  4. Estimate the Right Ascension (R.A.) and Declination (Dec.) of the Hunter Constellation. R.A. = 5h Dec. = 5  p. 6

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5. Estimate the Right Ascension (R.A.) and Declination (Dec.) of the Dragon Constellation. R.A. = 18h Dec. = 5  Star Chart 1 – Northern Region p. 7

Star Chart 2 – Equatorial Region p. 8 Big Dipper

Star Chart 3 – Equatorial Region p. 9

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Star Chart 4 – Southern Region p. 10

p. 11

Lab 11 celestial Globe April 24

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