Navigating the Night Sky: Using Star Charts Effectively

Name : Eric Chung Lab N o :4________ Partner(s) _________________ Date : 2/23/2023 NAVIGATING THE STAR USING A STAR CHART & CELESTIAL SPHERE Activity 1: Navigating the star using a star chart (or planisphere) 1- How do you know if a particular star or constellation (group of stars) will be up in the sky on a certain night? Use a star chart if available. If not, map each night and day for one year to understand when each star or constellation will re-appear. A star chart is a simple device that allows you to determine which stars or constellations are visible at particular times of the evening. The rising and setting times of stars and constellations can be determined. Use the star chart (picture of the star chart is available below for the students who do not have it) to answer the following questions: 2- Label north, south, east, and west on THE NIGHT SKY to the picture below as they appear on the star chart. Are east and west in the positions you expect with respect to the north? Explain. No, I expected them to be switched since East is usually to the right of North (when you look at it upside down). This is a picture of a star chart, this is useful for those students who do not have a star chart. 1

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You label this night sky. Label North, South, East, West, Polaris and Zenith. If you have difficulty to label it, just describe the position of the label with the text below. 3- Hold the star chart over your head with north on the chart pointing to the north. Are east and west where you expect them? No, they are not. They are switched. 4- What does this mean about how you are expected to use the star chart? You must hold it over your head so that your sight aligns with the compass. That way you will know precisely where the stars will appear in the sky. 5- What part of the star chart defines the horizons? These are your limits of viewing. The part of the star chart where the cardinal directions North, East, and West arelabeled defines the horizon. 6- Locate and label the position of Polaris, the North Star, on THE NIGHT SKY above. What is important about this point? Polaris is named the North Star because it points North regardless of your positioning on Earth. 3

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7- Where is the zenith on the star chart? Label it on THE NIGHT SKY above. South 8- Will you expect the pattern and position of constellations on the star chart to exactly match the display you will see in the sky? Explain why or why not. I would expect it to be accurate if I was in the 30 o -40 o north latitude area, as that is specifically what the star chart says it’s for. If I wasn’t, this would not be accurate at all. 9- The star chart is set to work in a range of latitudes. The chart you are using is exact at 40 o N latitude (or 30-40 o N), which is the latitude of Maryland’s northern border. From the “north” mark on the star chart, determine the number of degrees between the horizon and Polaris. Around 32 between the horizon and Polaris. 10-How is this related to the latitude where the star chart is exact? The latitude of a specific location is equivalent to the number of degrees between the north horizon and Polaris. Consequently, if that latitude is between 30 o and 40 o , the star chart will be accurate. 11-In Bowie (Maryland) the latitude is approximately 39 o N. How far above the northern horizon would you expect to find Polaris? Around 39 o above the horizon 12-If you were at the north pole of the Earth, would this star chart give you an accurate representation of the night sky? Why or why not? It doesn’t work because the North Pole is art a different latitude. 13-Set the chart for 15 December at 9:00 pm by holding the stationary portion of the chart, turning the sky dial until your time of night lines up with the observing date. Any object in the oval opening is visible at the position for the date and time. (Please use the setting above, first picture. This also serves as the star chart for those students who do not have it). Use this setting to answer the following questions. 4

a- Find the constellation Pegasus. In which direction in the sky would you look to find it? West b- Locate and list a constellation that is rising. Cancer c- Locate and list a setting constellation. Aquarius d- What constellation is at your zenith? Eridanus e- Find the constellation Orion. What is the declination or location of Orion's belt? East f- Sirius is the brightest star in the night sky. In which constellation is the star Sirius? Canis Major g- What are the declination and right ascension of Sirius? Right ascension = 6hr 45m Declination = -15 h- At what time will Sirius rise? 6:30 am i- At what time will Sirius set? 8 pm 5

14-Set the star chart for 10:00 pm on 04 July.(Please the setting below) 6

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a- Locate a constellation which is at the zenith: Hercules rising: Capricornus setting: Virgo b- The answers above are for summer. Would you get the same constellations in winter? Explain. It’s not going to be the same constellation, as you can see in the chart. c- Is Sirius visible at this time and date? No, we cannot see it on July 4 th 10pm 15-Slowly turn the sky dial or wheel. As you do that notice which constellations are always visible above the horizon. Record the names of three. 1. Cepheus 2. Draco 3. Ursa Minor The constellations you listed are called circumpolar constellations and are visible all the time (assuming it is dark enough). 16-What line of declination does a constellation have to be above to be circumpolar constellation? Above 60 o 17-In a total eclipse of the Sun the sky darkens just like at night. Would you see the circumpolar constellations if you were in the path of totality and the eclipse occurred at 12 noon? Explain. Yes, you can see some circumpolar constellations from the equator, but they will not appear to rotate around the sun. Instead, they will rise and set like all other stars. 7

18-Are the planets represented on this chart? Why or why not? It’s not fixed so we cannot predict the position of planets because it keeps changing. Activity 2: Celestial Sphere 1- Do some research and define what is a celestial sphere. A sphere where the observer is at the center while all celestial objects sit upon. After the last lab, you are now familiar with finding yourself on a sphere. The picture below shows the celestial sphere . It is an imaginary sphere of arbitrarily large radius centered on the Earth upon which all celestial bodies can be projected. At any one time, an observer on the Earth’s surface can only see half of the celestial sphere since the other half lies below the horizon. Although the rotation of the Earth is constantly bringing new regions of the celestial sphere into view, unless the observer is located at the equator , there will always be part of the celestial sphere that remains hidden. Due to the rotation of the Earth on its axis , the celestial sphere appears to rotate daily from east to west, and stars seem to follow circular trails around two points in the sky. These two points mark the intersection of the projection of the Earth’s rotation axis on the celestial sphere, and are called the celestial poles . The point directly overhead the observer is called Zenith, and the line on the celestial sphere joining the observer’s zenith with the north and south celestial poles is the celestial meridian . The projection of the Earth’s equator on the celestial sphere is called the celestial equator. Similarly, the Earth’s coordinate system of longitude (meridians) and latitude (parallels) can be projected on the celestial sphere. Giving rise to the celestial coordinates: right ascension (RA) and declination (Dec). Objects south of the celestial equator have negative declination values while objects to the north have positive declination values. 8

The right ascension is measured in hours and minutes and seconds but declination is measured in degrees and minutes. The declination of the celestial equator is zero degree like the Earth’s equator. The north celestial pole and south celestial pole have values of +90 o and -90 o respectively. 9

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Image of the celestial sphere. The red “Ecliptic” is the sun’s path throughout the year. 2- For the Northern Hemisphere, the axis of rotation is centered in Polaris , a star in the constellation Ursa Minor (or Little Bear) - sometimes called the Little Dipper. Polaris is not exactly at the axis of rotation, but it is pretty close. The pole star is circled in this picture: The North Star – Polaris is circled. The space between the two circled stars of Ursa Major is 5 degrees – and these stars point to Polaris. To measure objects in the night sky, you can follow this link http://astronomyonline.org/Observation/HowToMeasure.asp? Cate=Observation&SubCate=MP07&SubCate2=MP0702 If you were standing on the Earth’s north pole, how would you describe the location of Polaris? Straight up 10

3- The Southern hemisphere is not so lucky. This image has the south pole area circled, but there is no star associated with this region. The region of rotation (The South Pole) is circled – there is no associated star. The space between the two circled stars of Crux is 6 degrees, and these point to the pole region. How do you find the South celestial pole? The relation of the other constellations between Polaris and the southern pole. 4- On what two dates do the celestial equator and the ecliptic cross? These dates are called the equinoxes. Spring and fall equinox (March 21 st and September 22 nd ). 5- Which equinox is the zero line for the right ascension? Vernal equinox On this image, the greatest separation between the ecliptic and the celestial equator is called the solstice. There are two solstices the highest point and the lowest point. 11

6- Do some research and find out the dates of these solstices. June 21 st (summer solstice) and December 21 st (winter solstice). 7- What is the maximum angle of separation between the ecliptic and celestial equator? This is the tilt of Earth’s axis. 23.4 o 8- Using the skymap http://www.avastronomyclub.org/skymap/d/skymap.php , find which stars are located in these positions. Stars RA DEC Identity 1 11h 03m 43.70s 61 o 45’ 03” Dubhe 2 10h 08m 22.30s 11 o 58’ 02” Regulus 3 06h 23m 57.10s -52 o 41’ 45” Canopus 4 20h 41m 25.90s 45 o 16’ 49” Deneb 9- Using the same skymap, determine the right ascension and declination of the following stars: Stars Constellation RA DEC Rigel Orion 5hr 14m 32.30s -8 o 12’06.0” Sirius Canis Major 6hr 45m 8.90s -16 o 42’58.0” 12 Lowest point – Second solstice Highest point – First solstice

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Regulus Leo 10hr 8m 22.30s +11 o 58’02.0” Antares Scorpius 16hr 29m 24.40s -26 o 25’55.0” Deneb Cygnus 20hr 41m 25.90 +45 o 16’49.0” Activity 3: Planets The paths of the planets sometimes appear on sky charts, since planets (the Wanderers) constantly change position in the sky, not like the stars. Planets move slowly, relative to the background stars. They are found near the ecliptic in a band called the zodiac. Mercury stays within 25 degrees of the sun, so this planet is difficult to see. Mercury is visible sometimes just after sunset or just before sunrise. Venus is very bright, and is also visible in the morning or evening, staying within 45 degrees of the sun. Mars, Jupiter, and Saturn are often visible at night. Mars, the Red Planet, and Saturn are about as bright as the brightest stars, and Jupiter is a bit brighter. 10- Using another skymap https://in-the-sky.org/skymap2.php? year=2021&month=2&day=2&town=4744709 get the coordinates of Jupiter. Don’t forget to set your location ant today’s date and time. Date: February 23 rd 2023 Rising time: 1810 RA: 00h 39m Dec: +03 o 05’ 11-What constellation would Jupiter be in? Pisces 12-Would it be visible to you during evening hours (6 pm to 6 am)? Only visible from 1810 to 2046 13-Provide the names of all planets that are visible tonight (6 pm to 6 am) Jupiter and Mars are the visible planets tonight. 13

Lab4_Navigating_the_stars

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