Star & Planet Locator: In Class Problem Set

1. Circumpolar constellations are those that are visible the entire year. Would the number of circumpolar constellations increase, decrease, or stay the same if we were observing from Miami, FL, a latitude of 25 degrees? What if you were observing from Fairbanks, Alaska? Explain your reasoning.

In Miami, since Polaris would be closer to the northern horizon, the number of circumpolar constellations would be less than in Providence. In Fairbanks, since Polaris would be at a greater altitude, the number of circumpolar constellations would be more than Providence.

2. What time will the star Arcturus in the constellation Bootes rise on February 5? What time will it set?

It will rise around 10:30 pm and set around 12:30 pm.

3. What time and where on the horizon does the sun rise and set on my birthday, October 26? What is the greatest altitude of the sun in the sky on this day? Answer the same questions for one month earlier and one month later.

September 26: Rise – E at 6:00 am, Set – W at 6:00 pm. Noon altitude: 50o

October 26: Rise – ESE at 6:30 am, Set – WSW at 5:30 pm. Noon altitude: 35o

November 26: Rise – ESE at 7:00 am, Set – WSW at 5:00 pm. Noon altitude: 30o

4. What constellation is the sun located in today? On your birthday? On my birthday (October 26)? When would be the best time of the year to observe the constellation Scorpius around midnight? Today (December 5): Scorpius October 26: Virgo Early June

5. Why are only certain constellations designated as constellations of the Zodiac?

The ecliptic is the path of the sun against the background stars during the course of the year. It is the yearly migration of the earth along its orbit that is responsible for the changing position of the Sun.

6. The dashed line on the Locator is the ecliptic, the path the sun makes through the sky during the year against the background stars. The “equator” line on the Locator is the Celestial Equator, an extension of the Earth’s equator. These two lines intersect twice during the year. Locate the intersections when they appear in the Southern horizon along the meridian. Record the date as they appear in the South horizon window on the Locator. What is the significance of these dates? What dates are the ecliptic and equator furthest apart? What is the significance of these dates?

The ecliptic (sun) and Celestial Equator overlap at the equinox. The sun is north of the Celestial Equator near the summer solstice and it is south of the Celestial Equator near the winter solstice.

7. The entire sky rotates around Polaris. Why?

The North Celestial Pole of the Earth is aligned with Polaris. All of the stars appear to revolve around Polaris since the earth’s rotation is responsible for the rotation of the stars in the sky.

8. The stars and constellations are printed on the face of the Locator. Why aren’t the planets placed there as well?

The planets change position during the course of the year since they are in orbit around the sun like the Earth. So from our vantage point in the solar system, the planets are changing location against the background stars.

9. Place Sirius on the eastern horizon and determine the time it rises on July 4. Then determine the time it rises 20 days later, on July 24. Then determine the time it rises 20 days later on August 13. Does Sirius rise earlier or later as the year progresses? On average, how many minutes over 20 days? Minutes per day?

July 4th: 7:00 am July 24th: 6:15 am August 13: 4:15 am

It rises earlier each day. During the 40 days it rose 2 hours and 45 minutes earlier, or 165 minutes. That averages to a bit over 4 minutes per day the stars rise earlier each day.

10. Your friend buys a new telescope and wants you to come over tonight to observe some celestial objects. What time tonight would you see the constellation Orion at its highest point (due south)? 1:00 am When would you see some of the planets and where would you look? Jupiter on the meridian around 9:30 pm about 80o above the south horizon. Give the name of a circumpolar constellation you would see tonight and where would you find it? Cassiopeia (60o) above northern horizon. What does it look like? A big M or W (draw a diagram). What constellations and prominent stars would you find around midnight tonight? Orion with Rigel & Betelgeuse in the SE sky (about 40o), Taurus with Aldebaran to the upper right of Orion, Auriga with Capella directly above (north) of Orion. Show them Polaris. Where is it? 40o above the northern horizon.

11. Identify the following constellations: a. The Hunter - Orion f. The Charioteer - Auriga b. The Queen - Cassiopeia g. The Big and Little Bear – Ursa Major and Minor c. The Princess - Andromeda h. The Big and Little Dog – Canis Major and Minor d. The King - Cepheus i. The Bull - Taurus e. The Eagle - Aquila j. The Swan - Cygnus

12. Define the following: a. The ecliptic – Yearly path of the sun. d. Horizon – Where land meets sky – 0o altitude b. The meridian – N/S line bisecting sky e. Azimuth – Compass direction along horizon. c. Zenith – 90o overhead f. Altitude – Degrees above the horizon.

13. Identify the constellations where the following prominent stars can be found: a. Polaris – Ursa Minor f. Capella - Auriga b. Rigel - Orion g. Betelgeuse - Orion c. Arcturus - Bootes h. Vega - Lyra d. Antares - Scorpius I. Sirius – Canis Major (brightest star in night sky) e. Aldebaran - Taurus j. Procyon – Canis Minor