THE SKY AND CONSTELLATION TOUR:

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1 name TAKE HOME VERSION OF SKY-LAB #1 OR AN EXTRA CREDIT LAB THE SKY AND CONSTELLATION TOUR: 2. USING SKY CHARTS GET A COPY OF THE PRE-LAB OF THE FIRST SKY-LAB READ AND UNDERSTAND THAT PRE-LAB YOU WILL NEED TO KNOW ALL THE TERMS IN IT The Sky #2 Extra Credit Lab 1

2 CONSTELLATIONS, STAR NAMES, AND STAR CHARTS Just as the United States is divided into 50 states, the sky is divided in 88 irregular regions called constellations. Constellations make finding objects in the sky easier. Just as specifying that Staten Island is in the state of New York, we specify for example that Betelgeuse is in Orion. However, there are also reasons why we use right ascension and declination (i.e., exact coordinates) as you will find out. Actually, professional astronomers only use the exact coordinates. The stars that make up the constellations are not actually physically associated but are just patterns that resemble or honor animals, mythological characters, etc. Many of the constellation names are Greek in origin (e.g., Orion, Hercules and Andromeda), while others are more contemporary in nature (e.g., Microscopium and Telescopium). The Stars are named using several different systems. The brighter stars all have ancient names, while fainter ones are known by number only (although you can name those stars after someone - as a Christmas present). Apart from using popular star names (like Sirius, or even weirder ones like Zubenelgenube or Zubenesschamali), amateur astronomers use the names of constellations, and designate stars in that constellation by Greek letters. The brightest star is alpha, α, the second brightest one beta, β, then gamma, γ, etc (For the Greek alphabet check the ToolKit). Thus Sirius, the brightest star in Canis Major, is also known as Alpha Canis Majoris. Sometimes, you ll see this abbreviated as αcma. Similarly, Betelgeuse is called Alpha Orionis (or αori) and Rigel Beta Orionis (βori). In the constellation charts the brightest stars correspond to big blobs, while fainter ones correspond to smaller blobs. You will be using charts like this in the lab. Just as we produce maps from the globe, we also produce charts from the celestial sphere. The diagram below shows how these charts relate to the celestial sphere. Imagine that you peel the celestial sphere just like you would peel an orange. Make a cut along the dotted line B, peel off the cap, and then view the cap from above. This corresponds to the SC-2 chart. Similarly take the part of the peel from between the lines A & A, flatten it out, and you get the SC-1 chart. 2 Extra Credit Lab The Sky #2

3 PART I: USING SC-1 AND SC-2 a) Find the Pole star. What is its proper name, and what is its other name? and b) Give the names (like Alpha Centaurus) of the following stars: (Hint: Use the Greek Alphabet, which you can find in the ToolKit) the 6th brightest star in Taurus the 15th brightest star in Leo the 21st brightest in Auriga c) Locate (using the constellation charts) and give the proper names of: Kappa Orionis Alpha Bootis Beta Ursae Majoris c) Give both names for the two Pointer Stars in the Big Dipper that (when a line is drawn through them) point towards Polaris, the pole star. Pointer Star 1: and Pointer Star 2: and e) Which of the following stars is brightest and which faintest? δ Auriga γ Taurus η Canis Majoris f) Using only the SC-1 chart locate and list 4 star clusters g) Using only the SC-1 chart locate and list 4 nebulae i) Using only the SC-2 chart locate and list 3 galaxies The Sky #2 Extra Credit Lab 3

4 PART II: THE SKY DURING DIFFERENT SEASONS Have you noticed that different stars are visible during different seasons? Let s figure out why this is. Look at the diagram below. Let s ignore the rotation of the EARTH around its own axis (only for now) and consider the motion of the EARTH around the Sun. Imagine that there are some aliens out there on a planet that is still unknown, but that is orbiting around Arcturus. Arcturus is in the constellation Boötes and is visible in the summer. In fact, in the evenings in June it is the brightest star within about 20 degrees of your ZENITH. So if you wanted, you could wave to the aliens. Half a year later, sometime in December, you want to wave at the aliens again but Arcturus is not up. Look at the diagram below, and convince yourself that the sun would blind you when trying to locate Arcturus. You can do this game with any other star too, and the sky appears to change with the seasons. Clearly, the stars do not move but the sky appears to move because of the EARTH s motion around the sun. 4 Extra Credit Lab The Sky #2

5 SEASONS & CONSTELLATIONS Let s only consider stars that are in constellations along the ecliptic. The diagram below is the same as the previous diagram. In June, at midnight, when you look towards the ecliptic, you see that Sagittarius is transiting, but if you want to look at Sagittarius in December, you would have to look through the sun, and you d be blinded. The Sky #2 Extra Credit Lab 5

6 WHICH CONSTELLATION IS UP? 1. The table below summarizes which constellation in the zodiac you would see at midnight. Complete the Table. Month / Date constellation transiting at midnight RIGHT ASCENSION of that constellation Sun would be seen in this constellation June 21 Sagittarius 18 hours Gemini July Capricorn 20 hours Cancer August Aquarius 22 hours Leo September 21 Pisces 0 hours Virgo October Aries 2 hours November Taurus 4 hours December 22 Gemini January February March April May Cancer Leo 2. Answer the following questions: In March, which constellation would you be able to see best at midnight? What is the RA of that constellation? In May, which constellation would transit at midnight? What is the RA of that constellation? Today, which constellation is transiting at midnight? What is the RA of that constellation? In which constellation would you find the sun today? What is the RA of that constellation? 3. Do you get the idea? Explain below how RA correlates with the season. 4. How many hours in RIGHT ASCENSION does each month correspond to? And one week corresponds to hour many minutes in RIGHT ASCENSION? 6 Extra Credit Lab The Sky #2

7 PART III USING SKY CHARTS TO OBSERVE THE SKY You will be using all the information you learned in the last section to figure out in during which season and during what time of night you will be able to observe which stars. Use the constellation charts SC-1 and SC-2. In particular check out SC-1. The x-axis corresponds to right ascension (RA), and the y-axis to declination (DEC). We said previously, that stars with a RA of 0 hours will be transiting on September 21 at midnight. But let s assume we want to observe at 8 p.m. at night, i.e., 4 hours before midnight. Thus stars with a RA of -4 hours, or with an RA of 20 hours (i.e., 24-4 = 20 hours) will be transiting. Now check the SC-1 chart. On the x-axis you see RA. Find all stars that have an RA of 20 hours. Below 20h on the x-axis you find a date (in a smaller script) - it says September 20. So at 8 p.m. in the evening of September 20, stars with an RA of 20 hours are transiting. Using the previous Table and/or the SC-1 chart answer the following questions: [Note the SC-1 chart shows transits at 8pm, not at midnight!] Write down today s date. Which stars are transiting at 8 p.m. today? Which stars are transiting at 8 p.m. on August 21? Give the name of a star that will transit today at 10 p.m.: Give the name of a star that will transit on August 21 at 10 p.m.: Which constellation is transiting at midnight on June 21? Which constellation is transiting at 2AM on June 21? Which constellation is rising at 2AM on June 21? Which constellation is setting at 2AM on June 21? On which date will Capella transit at midnight? On which date will it transit at 8 p.m.? At which time will Capella transit today? At what time, today, will Betelgeuse transit? At what time, today, will the Andromeda Galaxy (M31) transit? The Sky #2 Extra Credit Lab 7

8 A QUIZ QUESTION #1 1. It is midnight. What season is it? Explain. 2. At what time would Vega be transiting in the above picture? Explain 8 Extra Credit Lab The Sky #2

9 QUIZ QUESTION #2 Hold the picture at arms length right in front of you. Imagine that this picture is part of the landscape in front of you. Imagine that the top of the picture somewhat curves around you. Image taken from the Anglo Australian Observatory at 1. At what latitude is this observatory? [You may consult your textbook. Check out the diagrams with the star trails.] Circle one of: 0, 10, 20, 30, 45, 60, 90 degrees. Explain how you arrived at this answer 2. What direction is the photographer facing? Circle one of E, W, N, S, SW, SE, NW, NE. Explain. 3. For how long was the shutter of the camera left open? Circle one of 1sec, 1min, 10 min, half an hour, one hour, two hours, 5 hours, 10 hours, 24 hours. Explain your answer. The Sky #2 Extra Credit Lab 9

10 LAB-REPORT IF YOU DO THIS LAB FOR EXTRA CREDIT, HAND IN THE ENTIRE LAB, INCLUDING YOUR PRE-LAB. State the purpose of the Lab Explain how the position of a star depends on the time of observation Explain how the position of a star depends on the season What have you learned from this Lab, and how useful do you think this information will be to you. 10 Extra Credit Lab The Sky #2

11 Now apply what you learned from this Lab. The Star Vega has a RIGHT ASCENSION of 18 h 40 m and a DECLINATION of 39 o. a) Determine at what time Vega will transit tonight (state your date). Show every step of how you reach your conclusion. [Explain in words how you arrive at your answers, then, do some additions and/or subtractions.] b) Make a drawing of the Celestial Sphere similar to the Figure in the quiz question #1; insert the position of Vega at its transit, and then draw its path throughout the night. c) Calculate the ALTITUDE of Vega during transit. Explain how you would determine this. [This tests if you understand the general concepts of the Celestial Sphere and whether you can visualize the motion of Vega in the sky.] d) If you think that you should be able to see Vega, go outside and look at the night sky check if your answers and drawings coincide with what you see. The Sky #2 Extra Credit Lab 11

12 Here are small versions of the charts; get the full size version from your instructor.