AST 1002 Slide Handouts: Topic A: Part 2 Page 1Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 2001Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20011Topic ATopic APart 2. What’s Up?(Web Version: 08-15-01)Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20012Census of the Night SkyAn inventory of sky objects by apparent brightness(By how bright things look)Sky ObjectsSky ObjectsHere are possible objects ( on next slide)1. Sun1. Sun2. Moon2. Moon3. ?3. ?Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20013QuestionQuestion What is the brightest appearing night-time celestial object not counting the Moon?(1) Alpha Centauri(2) Jupiter(3) North Star(4) Sirius(5) VenusVer. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20014Brilliant VenusEat HereOften visible just after sunset or before sunrise(and sometimes during daytime)Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 1998, Ver. 063098Brilliant VenusEat HereSometimes mistaken for airplane lights . . . or a UFO !Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 1998, Ver. 063098Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20016Sky ObjectsObjectSunMoon (Full)VENUS??Can you fill innext two objects?(see next slide)AST 1002 Slide Handouts: Topic A: Part 2 Page 2Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 2001Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20017What Have We Here?JupiterVenusLake Alice (UF Campus)1998 April 236:15 a.m. EDT(40 min. before sunrise)Crescent Moon(3 days before New)(reflection in water)? ?Entire lunaroutline visible(“New moon in old moon’s arms”)Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20018Sky ObjectsObjectSunMoon (Full)VENUSJUPITERNext ?Another planet?Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 20019Sky ObjectsObjectSunMoon (Full)VENUSJUPITERMARSObjectSiriusBrightest nighttime starStill another planet!SiriusEat HereDept. Astronomy – University of Florida – Copyright © H.L. Cohen 1997, Ver. 011297Sirius, a brilliant whitish star, not the North Staris brightest nighttime starBut Venus is about 15 times brighter!Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200111Know the Planets & SiriusObject Mag.Sun -27Moon (Full) -13VENUS* -4½ to -3 JUPITER* -2½ to -1 MARS* -3 to +2Object Mag.Sirius** -1½Canopus - ¾MERCURY* -½ to +1Several Stars 0SATURN* -½ to +1*The naked eye planets **Brightest nighttime starTable 1 in Study Guide (also on web)Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200112What is a Planet?§ Ancient literature often cites seven planets (notfive)• What are the other two?• Why included?§ To answer must understand“classical meaning” of a planetAST 1002 Slide Handouts: Topic A: Part 2 Page 3Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 2001Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200113Wandering “Stars”Ancient peoples observed wandering starsLast Week TodayOne “star” has “moved”• The four corner stars are “fixed”• The middle “star” has moved or “wandered”Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200114Planets & Stars§ The Ancients knew seven “wanderers”§ What are their names?§ AnswerThe five “naked eye” planets + ? + ?§ “Planet ” is from ancient Greek meaning . . .“a wanderer ”? + ?Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200115Sky List IncompleteObject Mag.Bright Stars* ½ to +1½ Another “50” +1½ to +2Polaris (N. Star) +2URANUS** +5½GalileanSatell. +5½Object Mag.Rural Limit +6½Bright Asteroids +6 NEPTUNE** +9 Binoculars +10 PLUTO** +13 to +15*About 15 **Non-naked eye planetsExamples suggest “flavor of what’s up”Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200116List Shows MagnitudesObject Mag.Bright Stars* ½ to +1½ Another “50” +1½ to +2Polaris (N. Star) +2URANUS** +5½GalileanSatell. +5½Object Mag.Rural Limit +6½Bright Asteroids +6 NEPTUNE** +9 Binoculars +10 PLUTO** +13 to +15*About 15 **Non-naked eye planetsVer. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200117Magnitudes § To appreciate table need knowledge of magnitudesMagnitude = brightness (not size)u Even simple star charts use them . . .Bright Faint(Different size dots simulate different brightness or magnitudes)Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200118Classical Magnitude System§ An early Greek system(Hipparchus, c. 120 B.C.)§ Naked eye stars put insix magnitude classes• Brightest = magnitude +1• Faintest = magnitude +6123456FaintestBrightestDecreasingBrightnessAST 1002 Slide Handouts: Topic A: Part 2 Page 4Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 2001Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200119Numbers of StarsBrightest starsmost common1st mag. — Approx. 206th mag. — Thousands123456FaintestBrightestVer. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200120Magnitudes Now§ Based on original system§ Magnitude classes now acontinuous scale§ Scale goes fromNegative (very bright)toPositive (very faint)...- 5.00- 4.00- 3.00- 2.00- 1.000.00+ 1.00+ 2.00+ 3.00+ 4.00+ 5.00+ 6.00+ 7.00+ 8.00+ 9.00+10.00... Ver. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200121...- 5.00- 4.00- 3.00- 2.00- 1.000.00+ 1.00+ 2.00+ 3.00+ 4.00+ 5.00+ 6.00+ 7.00+ 8.00+ 9.00+10.00... See Study GuideVery bright objects have negative magnitudes• Sun -27• Full Moon -13• Venus -4½• Jupiter -2½• Sirius -1½• etc.SiriusVenusPolarisJupiterNeptuneVery BrightVery FaintSee Table 1Approx. Naked Eye LimitVer. 081501Dept. Astronomy – University of Florida – Copyright © H.L. Cohen 200122Don’t Memorize Magnitudes!Object Mag.Sun -27Moon (Full) -13VENUS* -4½ to -3 JUPITER* -2½ to -1 MARS* -3 to