1. 8 March 2011 -- subst for Roberta Stars

2. 8 March 2011 -- subst for Roberta

3. ( PARENTHETICAL ) STAR NAMES SIRIUS  CMa ( Alpha Canis Majoris ) HR 2491 HD 48915 SAO 151881... and other STAR CATALOGS

4. 8 March 2011 -- subst for Roberta DISTANCES OF STARS

5. 8 March 2011 -- subst for Roberta DISTANCES OF STARS EARLIEST IDEA: PARALLAX

6. 8 March 2011 -- subst for Roberta TRIGONOMETRIC PARALLAX

7. 8 March 2011 -- subst for Roberta STELLAR PARALLAX

8. 8 March 2011 -- subst for Roberta ( SOMETIMES IT’S CALLED ANNUAL PARALLAX )

9. 8 March 2011 -- subst for Roberta PARALLAX GETS SMALLER AS DISTANCE GROWS LARGER ( and vice-versa )

10. 8 March 2011 -- subst for Roberta

11. LET’S CHOOSE GOOD MEASUREMENT UNITS …

12. 8 March 2011 -- subst for Roberta ANGLES 360 degrees ( 360 ° ) in a circle 60 arc-minutes ( 60 ) in 1 ° 60 arc-seconds ( 60  ) in 1 

13. 8 March 2011 -- subst for Roberta ANGLES 360 degrees ( 360 ° ) in a circle 60 arc-minutes ( 60 ) in 1 ° 60 arc-seconds ( 60  ) in 1  so … 1,296,000 arc-seconds in a circle! An arc-second ( arcsec ) is small;

14. 8 March 2011 -- subst for Roberta ANGLES 360 degrees ( 360 ° ) in a circle 60 arc-minutes ( 60 ) in 1 ° 60 arc-seconds ( 60  ) in 1  1 inch subtends 1 arcsec at a distance of 3.3 miles.

15. 8 March 2011 -- subst for Roberta ANGLES 360 degrees ( 360 ° ) in a circle 60 arc-minutes ( 60 ) in 1 ° 60 arc-seconds ( 60  ) in 1  we measure parallaxes in arcsec.

16. 8 March 2011 -- subst for Roberta UNITS FOR DISTANCES ASTRONOMICAL UNIT ( AU ) = AVERAGE DISTANCE OF SUN = RADIUS OF EARTH’S ORBIT

17. 8 March 2011 -- subst for Roberta UNITS FOR DISTANCES ASTRONOMICAL UNIT ( AU ) = AVERAGE DISTANCE OF SUN = RADIUS OF EARTH’S ORBIT = about 150 million kilometers = about 93 million miles

18. 8 March 2011 -- subst for Roberta

19. STAR’S DISTANCE = _____________________ 206,265 AU PARALLAX IN ARCSEC

20. 8 March 2011 -- subst for Roberta UNITS FOR DISTANCES ASTRONOMICAL UNIT ( AU ) = AVERAGE DISTANCE OF SUN = RADIUS OF EARTH’S ORBIT

21. 8 March 2011 -- subst for Roberta UNITS FOR DISTANCES 1 PARSEC = 206,265 AU (explain) usually abbrev. “PC”

22. 8 March 2011 -- subst for Roberta STAR’S DISTANCE = _____________________ 1 PARSEC PARALLAX IN ARCSEC

23. 8 March 2011 -- subst for Roberta UNITS FOR DISTANCES 1 PARSEC = 206,265 AU = almost 31 trillion kilometers, urggh.

24. 8 March 2011 -- subst for Roberta By the way … 1 parsec = 3.26 LIGHTYEARS. Nearest star is 1.3 pc or 4.3 ly.

25. 8 March 2011 -- subst for Roberta c. 1590: TYCHO BRAHE TRIED TO DETECT PARALLAX AND FAILED. (explain)

26. 8 March 2011 -- subst for Roberta c. 1680: NEWTON PREDICTED PARALLAX WOULD BE VERY SMALL, D ( nearest star ) = maybe 300,000 AU (explain how he guessed)

27. 8 March 2011 -- subst for Roberta

28. SUCCESSFUL PARALLAXES, AROUND 1839: 61 CYGNI (BESSEL, GERMANY) VEGA (STRUVE, RUSSIA) ALPHA CENTAURI (HENDERSON, S.AFRICA)

29. 8 March 2011 -- subst for Roberta ALPHA CENTAURI A, B, C DISTANCE = 270,000 AU 1.3 PC ( parsec ) 4.3 LY ( lightyear )

30. 8 March 2011 -- subst for Roberta ALPHA CENTAURI 9 MILES

31. 8 March 2011 -- subst for Roberta THE THREE STARS OF ALPHA CENTAURI A : YELLOW, SOMEWHAT BRIGHTER THAN THE SUN; B : ORANGE, 40% AS BRIGHT AS THE SUN; C : RED, 1 / 17000 AS BRIGHT AS THE SUN. “PROXIMA CENTAURI”

32. 8 March 2011 -- subst for Roberta PARALLAX DISTANCES SHOWED THAT STARS ARE NOT ALIKE

33. 8 March 2011 -- subst for RobertaAst 1001, 29 March 2010 -- KD HIPPARCOS SATELLITE MEASURED ULTRA - PRECISE PARALLAXES

34. 8 March 2011 -- subst for Roberta

35. NEXT: MOTIONS OF THE STARS IN SPACE

36. 8 March 2011 -- subst for Roberta PROPER MOTION OF BARNARD’S STAR ( 6 L.Y. AWAY )

37. 8 March 2011 -- subst for Roberta THE SUN, FOR EXAMPLE, MOVES ABOUT 15 KILOMETERS PER SECOND = 33,000 M.P.H. = 3 A.U. PER YEAR.

38. 8 March 2011 -- subst for Roberta

39. “STATISTICAL PARALLAX” BASED ON PROPER MOTIONS ( explain ) -- GOOD ONLY ON AVERAGE, BUT OK OUT TO ABOUT 5000 L.Y. --

40. 8 March 2011 -- subst for Roberta REMEMBER THE DOPPLER EFFECT?

41. 8 March 2011 -- subst for Roberta RADIAL VELOCITY measured with the Doppler effect … Examples …  20 km / s means the star is moving toward us ( “blueshift” ) + 15 km / s means it’s moving away ( “redshift” )

42. 8 March 2011 -- subst for Roberta

44. WE QUOTE THE BRIGHTNESS OF EACH STAR AS A “MAGNITUDE”.

45. 8 March 2011 -- subst for Roberta ABOUT 2100 YEARS AGO, HIPPARCHUS (= HIPPARCOS) MADE A LIST OF 1000 STARS...

46. 8 March 2011 -- subst for Roberta ABOUT 2100 YEARS AGO, HIPPARCHUS (= HIPPARCOS) MADE A LIST OF 1000 STARS... BRIGHTEST: “STARS OF THE FIRST MAGNITUDE”. THEN “SECOND MAGNITUDE”, THIRD, ETC. FAINTEST WE CAN SEE: “SIXTH MAGNITUDE”.... simple “eye estimates”.

47. 8 March 2011 -- subst for Roberta MANY CENTURIES LATER, ASTRONOMERS LEARNED HOW TO MEASURE THE STARS’ MAGNITUDES... for example -- Aldebaran... m = 0.85 (fairly bright) Tau Ceti... 3.50 HD 191849... 7.97 (faint)

48. 8 March 2011 -- subst for Roberta

49. THE MAGNITUDE SCALE TURNED OUT TO BE LOGARITHMIC -- LIKE DECIBELS USED TO MEASURE SOUND. 80 DECIBELS = 1 90 DB = 10 100 DB = 100... and so on.

50. 8 March 2011 -- subst for Roberta THE MAGNITUDE SCALE IS LOGARITHMIC -- 1.0 magnitude = 100 2.0 = 39.8 (2.512 x fainter)

51. 8 March 2011 -- subst for Roberta THE MAGNITUDE SCALE IS LOGARITHMIC -- 1.0 magnitude = 100 2.0 = 39.8 (2.512 x fainter) 3.0 = 15.8

52. 8 March 2011 -- subst for Roberta THE MAGNITUDE SCALE IS LOGARITHMIC -- 1.0 magnitude = 100 2.0 = 39.8 (2.512 x fainter) 3.0 = 15.8 4.0 = 6.31 5.0 = 2.512 6.0 = 1.0

53. 8 March 2011 -- subst for Roberta THE MAGNITUDE SCALE IS LOGARITHMIC -- 1.0 magnitude = 100 2.0 = 39.8 (2.512 x fainter) 3.0 = 15.8 4.0 = 6.31 5.0 = 2.512 6.0 = 1.0 7.0 = 0.398... etc.

54. 8 March 2011 -- subst for Roberta THE MAGNITUDE SCALE IS LOGARITHMIC -- THE DIFFERENCE BETWEEN TWO STARS’ MAGNITUDES CORRESPONDS TO THE RATIO OF THEIR BRIGHTNESS. Example: star A has m = 2.3, star B has m = 7.3; Difference... 5.0 magnitudes. So star A is 100 x as bright as star B.

55. 8 March 2011 -- subst for Roberta “APPARENT VISUAL MAGNITUDES” Sun: m = -27 Moon: -10 Venus: -4 Mars: -2.5 Sirius: -1.4 Vega: 0.0 Antares: 1.0 Polaris: 2.3

56. 8 March 2011 -- subst for Roberta “APPARENT VISUAL MAGNITUDES” BRIGHTEST STAR (SIRIUS): m = - 1.4 20 th –BRIGHTEST STAR: +1.5 FAINTEST VISIBLE:... about 6.5 WITH BINOCULARS: about 8 6-INCH TELESCOPE: about 12 PLUTO: 14 LIMIT WITH MODERN DETECTORS ON BIG TELESCOPES: 20 -- 28

57. 8 March 2011 -- subst for Roberta MAGNITUDES ALSO GIVE COLORS. WE USE FILTERS, FOR INSTANCE ‘V’ = “visual”, yellow-green, ‘B’ = “blue” U B V R I J K L... filters

58. 8 March 2011 -- subst for Roberta MAGNITUDES ALSO GIVE COLORS. WE USE FILTERS, FOR INSTANCE ‘V’ = “visual”, yellow-green, ‘B’ = “blue” ( B magnitude ) - ( V magnitude ) is a measure of the star’s color. B – V = -0.3... blue, very hot = +0.6... like the Sun = +2... red, cool star

59. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF A STAR

60. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF A STAR upper-case M ( m is apparent magnitude.)

61. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF A STAR M = THE APPARENT MAGNITUDE m THAT THE STAR WOULD HAVE AT A STANDARD DISTANCE OF 10 PARSECS = 33 LIGHTYEARS

62. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF A STAR TO CALCULATE M, WE NEED TO KNOW BOTH m AND D.

63. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF STARS M FOR THE SUN = + 4.8

64. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF STARS M FOR THE SUN = + 4.8 FAINTEST RED DWARF STARS: M = + 18

65. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF STARS M FOR THE SUN = + 4.8 FAINTEST RED DWARF STARS: M = + 18 MOST LUMINOUS STARS: M = - 12

66. 8 March 2011 -- subst for Roberta LUMINOSITY OR ABSOLUTE MAGNITUDE OF STARS M FOR THE SUN = + 4.8 FAINTEST RED DWARF STARS: M = + 18 MOST LUMINOUS STARS: M = - 12 OVERALL RANGE: 30 MAGNITUDES, = A LUMINOSITY FACTOR OF 1,000,000,000,000 ( A TRILLION )

67. 8 March 2011 -- subst for Roberta