Phys 1533 Descriptive Astronomy

1. Required texts: • Astronomy: A Beginner’s Guide to the Universe, 5th ed by Chaisson & McMillan • Lecture Tutorials for Introductory Astronomy, 2nd ed by Prather, Slater, Adams, & Brissenden -- BRING THIS TO CLASS EVERYDAY! Phys 1533 Descriptive Astronomy Instructor: Dr. Jackie Dunn

2. A Little About Me • Assistant Professor of Physics • Ph.D. in astrophysics from Texas Christian University (Fort Worth, TX) • Office: McCoy Hall, room 219D • Email: jackie.dunn@mwsu.edu • Phone: (940) 397-4184

3. Course Structure • Lecture • Think-Pair-Share Questions • Lecture Tutorials • Open Discussions How do we learn? • By doing! • Just listening to lecture is not enough.

4. Education Research • Students retain about 10% what they here in pure lecture-style courses. • At the University of Arizona, students took a 68 question test: • Scored 30% pre-course. • Scored 50% post-lecture. • Scored 75% post-lecture tutorials.

5. Grading • Semester Project: 15% • Labs: 15% • Participation: 10% • 2 Exams: 20% each (40% total) • Final Exam: 20% (Yes, it’s cumulative.)

6. Grading Participation • There will be in-class activities nearly every class period. • These will occasionally be collected. • Grading scale: • 80% participation points: 10 pts • 70 to 79% participation points: 8 pts • 60 to 69% participation points: 6 pts • 50 to 59% participation points: 4 pts • 40 to 49% participation points: 2 pts • Below 40%: 0 pts

7. Think-Pair-Share Example Using your letter cards (and without discussing with anyone), determine how to represent the two answer choices: (1) “E” and (2) “I have no idea.”

8. What is astronomy? • The study of the universe. • It involves concepts from physics and math, as well as from chemistry, geology, and biology. • It is NOT about making predictions about people’s lives (that would be astrology, which is NOT based on science).

9. Has the study of astronomy had an impact on your day-to-day life?(a) Yes (b) No Any particular topics you would like to cover this semester?

10. A Little Perspective

15. The above image is a zoomed in version of one of the darkest regions in the image to the left.

16. Our Place in Space • Planet (Earth) • Star (Sun) • Galaxy (Milky Way) - Gravitationally bound grouping of a large number of stars. • Universe (everything) - The universe includes everything in existence. There are billions of galaxies.

17. Constellations in the Sky • On any night, you can see some 3000 stars with the unaided eye. • People tend to see patterns (your eyes and brain like to connect the dots). This human habit has given us the constellations. • Northern hemisphere: named after mythological heroes and animals. • Southern hemisphere: named by northern explorers when they traveled south. • There are 88 named constellations in all.

18. A Couple Constellations Leo, the Lion Ursa Major, the Great Bear

19. The Celestial Sphere • Ancient observers deemed the stars to be fixed to a sphere that rotated around the earth - we call this the celestial sphere. • Ancient astronomers thought the stars moved, but now we know the apparent motion of the stars is caused by the earth’s rotation.

20. Celestial Coordinates • Declination (latitude) • Right Ascension (longitude)

21. Celestial Sphere Rotation Star B 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 Horizon 4 Celestial Sphere Rotation Figure 2 Is the horizon shown a real physical horizon, or an imaginary plane that extends from the observer and Earth out to the stars? Can the observer shown see an object located below the horizon? Is there a star that is in an unobservable position? When a star travels from being below the observer’s horizon to being above the observer’s horizon, is that star rising or setting?

22. Tutorial: Position (p. 1) • Work with a partner. • Read the instructions and questions carefully. • Talk to each other and discuss your answers with each another. • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer ask another group. • If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask me for clarification.

23. Celestial Sphere Rotation Star B 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 Horizon 4 Celestial Sphere Rotation Figure 2 In what direction is the observer facing? toward the South toward the North toward the East toward the West

24. Imagine that from your current location you observe a star rising directly in the east. When this star reaches its highest position above the horizon, where will it be? • high in the northern sky • high in the southern sky • high in the western sky • directly overhead

25. Is there a location from which an observer would see a star rise due east, move directly overhead, and then set due west? • No, that never happens. • Only if the observer is located in the southern hemisphere. • Only if the observer is located in the northern hemisphere. • Only if the observer is located at the north pole. • Only if the observer is located at the equator.

26. In what direction would an observer located at the north pole have to look to see the north star? • Along the northern horizon. • Along the southern horizon. • Directly overhead. • About 30 degrees above the northern horizon. • The north star cannot be seen from the north pole.

27. In what direction would an observer located at the equator have to look to see the north star? Along the northern horizon. Along the southern horizon. Directly overhead. About 30 degrees above the northern horizon. The north star cannot be seen from the north pole.

28. Where would the observer look to see the star indicated by the arrow? Celestial Sphere Rotation Star B 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 Horizon 4 Celestial Sphere Rotation Figure 2 • high in the Northeast • high in the Southeast • high in the Northwest • high in the Southwest

29. How long did it take to get this picture?Take out a piece of paper and put your name on it along with your answer!!

30. Earth’s rotation causes the Sun, Planets, Moon and stars to appear to move when viewed from Earth

31. Day-to-Day Changes • Solar day - period from one sunrise to the next (24 hours) • Diurnal motion - apparent daily progress of the Sun and other stars across the sky due to Earth’s rotation. • Sidereal day - a day measured by the stars. Due to Earth’s orbit around the Sun, this is 3.9 minutes shorter than a solar day.

32. Tutorial: Motion (p. 3) • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group. • If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask for help.

33. Seasonal Changes • Since Earth revolves (orbits) around the sun, the darkened part of the earth faces a slightly different direction each night. This is why we see difference constellations at different times of the year. • Ecliptic - the path traced out by the sun on the celestial sphere. The constellations the sun passes through on the ecliptic are collectively known as the zodiac.

34. Why do we experience summer and winter? • The earth is at different distances from the sun. • The sun experiences seasonal variations in intensity. • The tilt of the earth affects how much direct light we get, which results in the summer and winter seasons.

35. Seasons and Tilt

36. Seasonal Changes • Summer solstice - when the sun is at its northernmost point above the celestial equator. This is the northern hemisphere’s longest day of the year. • Winter solstice - when the sun is at its southernmost point below the celestial equator. This is the northern hemisphere’s shortest day of the year. • Equinoxes - two points where the ecliptic intersects the celestial equator. The day and night are of equal length at these two points. • Autumnal equinox - on September 21. • Vernal equinox - on or near March 21. • One tropical year - the interval of time from one vernal equinox to the next (365.242 days).

37. Long-Term Changes • Sidereal year - time required for Earth to make one orbit around the sun relative to the stars (365.256 days). • Precession - Earth’s axis changes direction over time (like a spinning top).

38. Precession

39. Your Astrological Sign ROUGHLY, it is the constellation that the Sun is covering up during the day you are born if you were born 2000 years ago.

40. Zodiac - The 13 Zodiacal constellations that our Sun covers-up (blocks) in the course of one year (used to be only 12) • Aquarius • Pisces • Aries • Taurus • Gemini • Cancer • Leo • Libra • Virgo • Scorpius • Ophiuchus • Sagittarius • Capricornus

42. The changing phases of the Moon originally inspired the concept of the month

43. Lunar Phases • Moon’s appearance undergoes a regular cycle of changes or phases. • New moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, waning crescent, and back to new moon.

45. How long does it take to complete the full cycle of moon phases? • About a day • About a week • About a month • About a year • None of the above

46. Lunar Cycle • Sidereal month - the time it takes the moon to complete one revolution around the earth (27.3 days). • Synodic month - the time it takes the moon to complete one full cycle of phases (29.5 days).

47. Tutorial: The Cause of Moon Phases (p. 79) • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group. • If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask for help.

48. During any given phase, how much of the moon’s surface is illuminated by the sun? • All of the surface. • None of the surface. • Half of the surface. • Depends on what phase.

49. Eclipses • An eclipse occurs during full or new moon when the sun, earth, and moon all line up just right. • Partial eclipse - what happens when the alignment is off just a bit. • Total eclipse - happens only when the alignment is perfect. • When the sun and moon are in opposite directions as viewed from Earth, we get a lunar eclipse. • When the sun and moon are in the same direction as viewed from Earth, we get a solar eclipse.

50. Lunar Eclipse