Merrimack College Astronomy 1101

Transcription

1 Merrimack College Astronomy 1101 Spring 2017 Ralph P. Pass 1

2 Lecture 5 - Outline Brief Review Constellations Coordinates Get to Galileo's Time 2

3 3

4 4

5 5

6 6

7 Observations Daily Stars Yearly Stars Yearly Snapshots Funny Stars 7

8 The Path of the Sun Ecliptic (Path of Sun) Lines of Longitude And Latitude Equator 8

9 What we 'know' Earth is round Earth size (8000 miles in diameter) Moon Distance (50 times Earth Radius) Moon Size (2000 miles in diameter) 9

10 Cosmology Circa 400BC Observations Things in the sky go around the earth once per day (more or less) Fixed stars do not move with respect to each other Wandering stars have different speeds with the Moon being fastest, then Mercury, Venus, Sun, Mars, Jupiter, and Saturn The wandering stars, fixed stars, funny (or strange) stars do not fall to earth We do not feel constant and consistent wind and everything thing we drop falls down 10

11 Cosmology Circa 400BC So, it was pronounced by Aristotle (and accepted with religious fervor) that the flat earth was the center of the universe (He actually said it was round, but his followers forgot that part) and it did not move (or rotate) The Sun and the Moon were perfectly smooth spheres (the perfect or ideal shape) without blemish That crystalline spheres (8) held the wanderers and the fixed stars and these spheres were centered on the Earth in the order (from Earth) of Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and the fixed stars The spheres rotated about the earth with periods of about a day. Anything transient was in the atmosphere (below the sphere of the moon) Stars do not change (no new stars, no dying stars) 11

12 In 435 B.C., the Greek philosopher Anaxagoras suggested that the sun was not just a small glowing circle of light. He maintained that it was a glowing rock a hundred miles across. For that outrageous statement, he was exiled from Athens. 12

13 Measuring Distances If 360 degrees is a complete circle, how big is the moon??? 13

14 Measuring Distances If 360 degrees is a complete circle, how big is the moon??? 0.5 degrees!! So it would take 720 moons to go all around the sky Question: Does the moon appear to be bigger or small when rising compared to when it is high in the sky? 14

15 Measuring Angles - I 15

16 Measuring Angles - II 16

17 Measuring Angles - III Remarkably, if you hold your hand straight out, the angular separations are constant (more or less) from one person to another For example, one fist at arms length is 10º Pinkie tip to thumb tip of a spread hand is about 20º 17

18 Homework Due 02/07/17 Find Orion Measure the distance from Betelgeuse to belt, Rigel to belt, Betelgeuse to Rigel Turn in: Date, time, and place, three observations, and your name 18

19 Observing the ISS Tonight 6:27pm to 6:32pm Mostly in the north west 19

20 Looking South 20

21 Looking North 21

22 Calculations Sun Speed Moon Speed Types of time 22

23 Who Named and Shaped the Nations (or States) 23

24 24

25 Pegasus - Stylized 25

26 Pegasus Planetarium Program 26

27 Pegasus With Figure 27

28 Pegasus Another View 28

29 Orion - Stylized 29

30 Orion Planetarium Program 30

31 Orion With Figure 31

32 Orion Second Planetarium 32

33 Without Constellation Lines 33

34 Black on White 34

35 Orion, yet again 35

36 Orion, yet again Betelgeuse The Belt The Shield M42 Rigel Sirius Lepus, the Rabbit 36

37 Some Star names Betelgeuse from Beit Algueze or Bed Elgueze or Ibt al Jauzah (Armpit of the Giant or Arm of the Central One Rigel Rijl Jauzah al Yusra (Left Leg of the Giant Sirius The Sparkling One 37

38 Cassiopeia and family Until now we have talked about one constellation or figure in the sky This soap opera has six characters which we will introduce, one at a time 38

39 Cassiopeia Queen, Ethiopia 39

40 Cepheus King 40

41 Andromeda Beautiful Daughter 41

42 The Soap in the Opera Cassiopeia bragged that her daughter Andromeda was more beautiful that the Nereids, the daughters of the God Poseidon Poseidon created a sea monster to cause problems for Ethiopia and the King went to an Oracle to find out how to stop the problems The solution was to sacrifice Andromeda to the sea monster 42

43 Cetus Sea Monster 43

44 So, who is our Superhero? 44

45 Perseus Superhero 45

46 Superhero s Transportation Pegasus, Flying Horse 46

47 The stars in our story 47

48 Constellations They grew from the myths and stories and used star patterns to act as reminders All cultures did this Science killed imagination, so that given the opportunity to create new constellations (in the southern hemisphere) they created The Air Pump, The Telescope, The Microscope, The Sextant, The Table Mountain, The Fly 48

49 49

50 Constellations Now Whereas the constellations could overlap in ancient times, they do not today In the name of science we have covered the entire sky with 88 constellations no overlaps and no gaps At least we kept most of the names and we can remind ourselves of the stories 50

51 Locating Stars Where is the White House? 1600 Pennsylvania Avenue Washington, DC USA This is equivalent to identifying star locations by their constellation 51

52 Locating Stars Where is the White House? N W Latitude and Longitude The street address is good to about 100 yards, the latitude and longitude to 6 feet If you understand latitude and longitude and have a map, you can find any particular latitude and longitude 52

53 Coordinates on Spheres Name some significant reference points or lines on a globe. North Pole South Pole Equator Greenwich Meridian International Dateline Tropic of Capricorn Tropic of Cancer 53

54 Coordinates on Spheres Which can be uniquely determined and which are arbitrary? North Pole, South Pole, Equator, Tropic of Capricorn, Tropic of Cancer Greenwich Meridian, International Dateline 54

55 Coordinates on Spheres For a rotating sphere there are three unique points: two axes points and one farthest from the spin axis Maximum distance from spin axis Spin Axis 55

56 Coordinates on Spheres Points a maximum distance from the spin axis are the equator and form a Great Circle The equator is also the point where the sun passes equally far from directly overhead during the year The tropics are where the sun passes overhead exactly once per year Latitude is an angular measure of distance from the equator towards the poles 56

57 Coordinates on Spheres Between the two tropics the sun passes directly overhead twice a year How did the tropics get their names? Longitude has an arbitrary 0 point which has been internationally accepted as the Greenwich Meridian or the Prime Meridian The French still smart from losing the 0 point battle with the British (They call the Greenwich Meridian Paris plus 7 minutes ) Longitude is measured in degrees, just like latitude Somewhere the day must change, hence the international dateline 57

58 Star Coordinates Project the poles and the equator onto the celestial sphere and you get the North Celestial Pole (NCP), the South Celestial Pole (SCP), and the Celestial Equator. Project lines of latitude onto the sky The name for the angular distance from a point to the Celestial Equator is the DECLINATION of the point and is conceptually the same thing as latitude (A point with declination equal to your latitude will pass directly overhead) 58

59 The Path of the Sun Ecliptic (Path of Sun) Lines of Longitude And Latitude Equator 2/3/

60 Star Coordinates To do the equivalent of longitude in the sky we need to pick a 0 point, the point were the Sun crosses the Celestial Equator going North This is the Vernal Equinox also known as the First Point of Aries. Unlike longitude which is measured in degrees from the Prime Meridian, this angle in the sky is measured in time. 60

61 Star Coordinates The stars take one star day to rotate about the earth (One Sidereal Day) The distance from the 0 point is measured by how long after the Vernal Equinox is it before an object is in the same relative location Measured as 0h to 23h 59m s This coordinate is called RIGHT ASCENSION and is conceptually the same as East Longitude One Hour of Right Ascension is 15 degrees 61

62 62

63 Example Coordinates 40 Degrees Vega: 18h 36.9m +38º Degrees 20 Degrees 63

64 64

65 65

66 66