Before you Sit. Please Pick-up: Blue Information Sheet for Evening Observing. 1 Red and 1 Blue ticket for Observing/ Planetarium

Transcription

1 Before you Sit Please Pick-up: Blue Information Sheet for Evening Observing. 1 Red and 1 Blue ticket for Observing/ Planetarium

2 Evening Observing Observing at the Brooks Observatory: Three different weeks (M-Thu) for this semester: Sep (starting at 9pm) Oct (>8:30pm) Nov (>7:30pm) Suggestion: Go Earlier in the semester: Warmer, less crowding (better chance to look), better weather (less chance of a waster trip).

3 Announcements/ Assignments Need syllabus/schedule/abcd card? See me after class. Finish reading Chapter 2 by Thu. First graded online homework: Homework #1 due Friday, Sept. 3rd 11:45pm. Available now. Reminder: Lecture notes are posted on the course website after class.

4 M.A. Homework Notes Late Homework: 10% off per day. Grading: 2% bonus per hint not used (use them!). sorting -type questions: Only 3% off for wrong answers. Still need help with MasteringAstronomy.com? See me after class.

5 Review A C B D Which is the correct order of events, according to the current accepted scientific theory of the origin and evolution of the Universe? A) Birth of Universe, solar system forms, first stars and galaxies, first life on Earth B) First stars and galaxies, birth of Universe, solar system forms, first life on Earth C) Solar system forms, birth of Universe, first stars and galaxies, first life on Earth D) Birth of Universe, first stars and galaxies, solar system forms, first life on Earth

6 Review A C B D Which is the correct order of events, according to the current accepted scientific theory of the origin and evolution of the Universe? A) Birth of Universe, solar system forms, first stars and galaxies, first life on Earth B) First stars and galaxies, birth of Universe, solar system forms, first life on Earth C) Solar system forms, birth of Universe, first stars and galaxies, first life on Earth D) Birth of Universe, first stars and galaxies, solar system forms, first life on Earth

7 Last Time Earth s Rotation (once per day) causes sun/ stars/etc. to rise in the east, transit at their highest point at the meridian, and then set in the west. Zenith is the point directly overhead. The Stars you see depends on your latitude. Some stars are always up: they are circumpolar. Constellations: Just random groupings of stars invented by humans. The celestial sphere is an imaginary sphere where we place stars on a two dimensional grid, similar to latitude and longitude on earth.

8 Last Time 1 degree=60 arcminutes = 3600 arcseconds. The size of objects in the sky is measured as an angle. Without knowing its distance, we can t know its true size.

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10 Star Rise From Toledo, you observe a star rising due east. When this star reaches its highest position above the horizon, where will it be? A C B D A) high in the northern sky B) high in the eastern sky C) high in the southern sky D) high in the western sky E) directly overhead

11 Star Rise From Toledo, you observe a star rising due east. When this star reaches its highest position above the horizon, where will it be? A C B D A) high in the northern sky B) high in the eastern sky C) high in the southern sky D) high in the western sky E) directly overhead

12 Star Rise From Toledo, you observe a star rising due east. When this star reaches its highest position above the horizon, where will it be? A C B D A) high in the northern sky B) high in the eastern sky C) high in the southern sky D) high in the western sky E) directly overhead

13 Equator Star Trails Imagine sitting at the equator at night as the Earth turns. What would the stars look like? Horizon All stars rise and set Polaris is located on the horizon

14 Latitude and Longitude How did sailors know their location on the Earth before GPS?

15 How to find your latitude on Earth? Polaris Horizon at the North Pole, lat=90, altitude of polaris=90

16 How to find your latitude on Earth? at the Equator, lat=0, altitude of polaris=0 Polaris Horizon

17 Star Trails in between Altitude of North Star = your latitude! Mauna Kea, Hawai i

18 How to Find Polaris?

19 Imagine you are located in the Northern Hemisphere and see a star directly overhead (zenith). In what direction will you have to look to see this star set? A C B D A) southwest B) west C) northwest D) This star will never set.

20 Imagine you are located in the Northern Hemisphere and see a star directly overhead (zenith). In what direction will you have to look to see this star set? A C B D A) southwest B) west C) northwest D) This star will never set.

21 Seasons, Annual Motions, and Phases of the Moon

22 Apparent Motion of the Sun Annual (yearly) motion Earth orbits Sun once per year Sun seen in front of different constellations throughout year The sun slips day to day on the celestial sphere, moving from W to E relative to the background of stars.

23 SOHO Observes Solar Motion

24 What Time is It? Possible times: sunset, sunrise, midnight, noon

25 What Time is It? 6am: Sunrise Possible times: sunset, sunrise, midnight, noon

26 What Time is It? 12pm: Noon 6am: Sunrise Possible times: sunset, sunrise, midnight, noon

27 What Time is It? 6pm: Sunset 12pm: Noon 6am: Sunrise Possible times: sunset, sunrise, midnight, noon

28 What Time is It? 6pm: Sunset 12pm: Noon 12am: midnight 6am: Sunrise Possible times: sunset, sunrise, midnight, noon

29 The Day 1 day = time for object to return to same point on sky (e.g. transit to transit) Solar day (sun) Time from noon until next noon Sidereal day (star) Time for a star to return to same point.

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32 Annual Path of Sun Ecliptic path of sun around celestial sphere shape: circle Zodiac Set of 12 constellations containing Ecliptic Sun in each constellation for about one month (solar) signs of the zodiac

33 Ecliptic on Celestial Sphere Earth s axis tilted 23º with respect to orbit

34 Locations on Ecliptic Solstice: Sun stops (moving N or S) Summer Solstice Jun 21=1 st day of summer Sun appears farthest North (from celestial equator) Longest day of year Winter Solstice Dec 21=1 st day of winter Sun appears farthest South (from celestial equator) Shortest day of year

35 Locations on Ecliptic Equinox: equal night and day Vernal Equinox ~March 21 = 1st day of spring Sun on equator (crossing from S to N) Autumnal Equinox ~Sept 21 = 1st day of fall (autumn) Sun on equator (crossing from N to S) Equinoxes are intersection points of Ecliptic and Celestial Equator

36 The reason for Seasons

37 Cause of Seasons Changing distance to Sun? Orbit is ellipse; distance changes Good idea, BUT... Orbit almost circular Trivial change in distance (3%!) little change in heating Closest to sun in January So this predicts summer in January! (wrong) Both N and S hemispheres at same distance Predicts seasons same in N and S hemispheres (wrong)

38 Cause of Seasons Trivial change in distance (3%!) Predicts seasons same in N and S hemispheres (wrong) Changing distance to Sun? Orbit is ellipse; distance changes Good idea, BUT... Orbit almost circular little change in heating Closest to sun in January So this predicts summer in January! (wrong) Both N and S hemispheres at same distance

39 Climate and Latitude Sun s rays spread over large area = cooler concentrate in small area = warmer Warmest where sun directly overhead (at noon) cooler warmer cooler

40 Why Then? Due to 23.5 tilt of the earth s axis? Sun up for longer, and higher in the sky = More sunlight = warmer: Summer Sun up above horizon shorter time, and lower in the sky = Colder: Winter.

41 Why Then? Due to 23.5 tilt of the earth s axis? Sun up for longer, and higher in the sky = More sunlight = warmer: Summer Sun up above horizon shorter time, and lower in the sky = Colder: Winter.

42 Seasons: Interactive Figure See Fig. 2.13

43 Sunrise above the artic circle

44 One night, you see the star Sirius rise at exactly 7:36 PM. The following night it will rise A) slightly earlier B) at the same time C) slightly later A C B D

45 One night, you see the star Sirius rise at exactly 7:36 PM. The following night it will rise A) slightly earlier B) at the same time C) slightly later A C B D

46 One night, you see the star Sirius rise at exactly 7:36 PM. The following night it will rise A) slightly earlier B) at the same time C) slightly later A C B D

47 Does the Orientation of Earth s Axis Change with Time? 26,000 yrs!

48 The Earth Moves like a Top: Precession

49 What sign are You? Signs of the zodiac: designed to indicate which constellations the sun is in. Precession of the Earth s axis

50 What sign are You? Signs of the zodiac: designed to indicate which constellations the sun is in. Precession of the Earth s axis

51 The Moon The moon is about 1 quarter the size of the Earth It orbits the Earth every 27.5 days On average, it is 380,000 km away

52 Phases of the Moon Each complete cycle of the moon takes 29.5 days, hence the word month It is longer than the orbital period (27.5 days) because of the Earth s orbital motion: Just like solar vs. sidereal day!

53 Phases of the Moon 29.5 days New } Crescent Waxing First Quarter Gibbous Moon visible in the afternoon/ evening. Get fuller and sets later each day. Full } Gibbous Waning Last Quarter Crescent Moon visible in the late night/ morning. Get lesser and rises later each day.

54 What causes moon phases? A) Moon passes into the shadow of the earth. B) Relative orientation of Sun, Moon, and Earth determines the phase. C) Moon is made of cheese, and the north wind eats it day by day. A C B D

55 What causes moon phases? A) Moon passes into the shadow of the earth. A B B) Relative orientation of Sun, Moon, and Earth determines the phase. C D C) Moon is made of cheese, and the north wind eats it day by day.

56 Take Away Earth s orbit about the sun once per year controls the position of the sun and the seasons. The sun appears to move slowly on the celestial sphere. When the sun, earth, and moon are aligned, eclipses can occur (more next week!). Don t Forget: HW #1 Due next Friday.