Motions in the Sky. Stars Planets Sun Moon. Photos - APOD. Motions in the Sky - I. Intro to Solar System

Transcription

1 Motions in the Sky Stars Planets Sun Moon Photos - APOD 1

2 STARS: background for motion of other objects patterns - constellations zodiac: special set of constellations trace the apparent path of the Sun on a yearly basis 2

3 Auriga Cassieopia Corona Photos H. Fairweather Orion - Taurus - Auriga 3

4 Big Dipper (part of Ursa Major) 4

5 Kaufmann & Comins 4/e 5

6 Scientific Observations => measurements Angular measurement: 1 full circle = 360 o 1/2 circle =180 o east horizon to overhead to west horizon 1/4 circle = 90 o overhead to horizon Use your hand for a measuring tool!! 6

7 angular separation: measurement of distance between 2 stars or other astronomical objects angular diameter (or size): measurement of width of an object 7

8 angular separation: measurement of distance between 2 stars or other astronomical objects angular diameter (or size): measurement of width of an object angular diameter of Sun ~ 1/2 degree angular diameter of moon ~ 1/2 degree 8

9 POT O GOLD $$ = PEOPLE 9

10 POT O GOLD my share $$ = PEOPLE My share is directly proportional to size of pot. My share is inversely proportional to number of people. 10

11 Angular diameter (or size) is related to distance Angular diameter (or size) is inversely proportional to distance Angular diameter is related to actual size Angular diameter is directly proportional to actual size 11

12 Mathematical Relationship Physical Diameter Angular Diameter = Distance = Size to Distance Ratio = 57 Size to Distance Ratio for 1 degree 12

13 Motion of the Stars Rise in the east, set in the west with respect to the horizon on a daily basis this is westward motion How fast is this motion? 13

14 Motion of the Stars, Relative to the Horizon - Zeilik, 6/e 14

15 angular speed: how fast an object covers What do we know? an angular distance Stars go around once per day 1 complete circle = 360 o in one day = 24 hrs. angular speed = 360 o 24 hrs. = 15 o hour 15

16 The apparent motion of the stars, on a daily basis, with respect to the horizon is 15 degrees per hour. 16

17 circumpolar stars: stars continually above the horizon, never set below the horizon 17

18 Circumpolar Stars - H. Fairweather 18

19 Circumpolar Motion of the Stars - Zeilik 6/e 19

20 Concept Extension - Circumpolar Stars Kaufmann & Comins 4/e Where, on Earth, would you see stars with this motion? At the North Pole! 20

21 Concept Extension - Circumpolar Stars Kaufmann & Comins 4/e Where, on Earth, would you see stars with this motion? On the equator! 21

22 seasonal changes: which constellations we see changes with the seasons 22

23 PLANETS fairly bright, steady, less twinkle than stars move with respect to constellations, over a period of time Naked Eye: Mercury Venus Mars Jupiter Saturn Telescope: Uranus Neptune Pluto 23

24 Leo and Jupiter - H. Fairweather 24

25 Leo and Jupiter - H. Fairweather Jupiter 25

26 Motion of the Planets westward with respect to the horizon eastward with respect to the zodiac (in general) westward through the zodiac (in retrograde) 26

27 Motions of the Planets with respect to the horizon rise in the east, set in the west - westward motion on a daily basis with respect to the zodiac constellations each night, a planet progresses bit eastward with respect to the background stars need several weeks to clearly see this generally follows the path of the ecliptic (apparent path of the Sun through the Heavens) 27

28 Motions of the Planets retrograde continue watching, eventually the eastward progression pauses, then the planet moves westward with respect to the stars then pauses again and resumes westward motion backwards motion 28

29 Path of Mars Kaufmann & Comins 4/e 29

30 inferior planets Planets those closer to the Sun than Earth Mercury, Venus never far from the Sun in the sky visible as the morning and evening star maximum elongation: greatest angular distance from the Sun Venus ~ 46 o Mercury ~ 23 o 30

31 conjunction: two celestial objects appear close together in the sky Inferior planets retrograde in conjunction that is, near the Sun question is - why? 31

32 superior planets Planets those farther from the Sun than Earth Mars, Jupiter, Saturn opposition: planet is opposite the sky from the Sun (as seen from Earth) maximum elongation can be 180 o Superior planets retrograde at opposition, that is, when opposite the Sun. 32