Lab 11 - Physics & Astronomy

Astronomy 105 LaboratoryLAB 11

AST 105Review for Lab Exam

Ast 105 Lab ExamTuesday, April 15 at 6:30 pm in the Kennedy AuditoriumDon’t be late!!Items to bring…- One scantron (882-E)- two pencilsDo not bring…- cell phones or anything else for that matter(if your cell phone rings or is seen by a TA you will receive a zero)

Study!• About 3-5 questions from each lab exercise• Review Main concepts covered Procedures and measurements Questions and calculations Bring a scantron: 882-E Review material – Power point slides online

THE MOON

N.P.SynchronousRotationN.P.N.P.N.P.Does the Moon rotate on it’s axis?What is the Moon’s hidden side?N.P.

N.P.Phase: 1 st quarterRise Time:Set Time:NoonMidnightTransit: SunsetSunsetMidnightN.P.NoonSunrise

EastNorthSummerSolsticeEclipticSun’s PathVernalEquinoxAutumnalEquinoxCelestial EquatorSouth

EastMarch 7 @ 8:00 p.mNorthZenith32° XWest HorizonMeridianSouth

March 7 @ 8:00 p.mWest Horizonnot visibleEast HorizonEastMeridianWest

Sky Familiarization• A Few More Things to Remember Any vertical line on your SC-1 (north-south) is ameridian. Approximately one half of the stars on the SC-1are visible at any given time (12 hours of RA). Meridian moves eastward 4 minutes each day(Earth’s revolution) Meridian moves eastward 1 hour of RA for everyhour of time (Earth’s rotation)

SCIENTIFICMEASUREMENTS

Scientific Experiments / Observations• Physical quantities can never bemeasured with absolute precision

How Many Significant Figures0.089 21.089 412000 212001 5

Scientific Notation3.502 x 10 6decimal number (1-9)10 raised to aninteger powerNumber Significant Figures Scientific Notation9004 4 9.004 x 10 30.000007 1 7 x 10 -643 2 4.3 x 10 17,805,000,000 4 7.805 x 10 90.0408 3 4.08 x 10 -28.4 2 8.4 x 10 0

To multiply two numbers in scientific notation multiply thedecimal parts of the numbers and add the exponentsalgebraically.(4.0 x 10 4 )(2.0 x 10 3 ) =(4.0 x 2.0)(10 4 x 10 3 ) =(8.0) x (10 4+3 ) =8.0 x 10 7(6.0 x 10 2 )(2.0 x 10 5 ) = 12.0 x 10 7 = 1.2 x 10 8

Units• Provides numerical context for a measurement• Unit conversionEx. Convert 500 kilometers into centimeters1000 m = 1 km 1 m = 100 cm1000 m1 km = 1 and 100 cm1 m = 1500 km ×1000 m1 km×100 cm1 m = 5 × 107 cm

MERCURY’S ORBIT

Verifying Kepler’s 1stMercury’s OrbitMajor AxisSUNFFEqual Time Intervals010 20 30 40 50 60 70 80 90 100610 km110 1200.00.10.20.30.40.50.60.7AU 0.8

Verifying Kepler’s 2 ndEqual area in equal time.Mercury’s OrbitMajor AxisSUN010 20 30 40 50 60 70 80 90 100610 km110 1200.00.10.20.30.40.50.60.7AU 0.8

P24πG2Kepler’s 3 rd )P 2 =ka 3Finding the Sun’smass.am 3Mk42G( m Mmm Msun24GaP32mm MsunMsunM sun24GaP32

EMISSION SPECTRA

Formation of Emission andDark Line Spectra

THE EARTH’S ORBITAL VELOCITY

The Doppler EffectVelocity = 012345IncreasingVelocityvr ocIncreasingVelocity

V AArcturusV B? ?vAc Δλλ0From measuredDoppler Shift1.Orbital velocity of Earth2.Radial velocity of Arcturus3.Radius of the Earth’s Orbit o

THE HR DIAGRAM

Apparent Brightness of Stars• Stellar Luminosity -- Total amount of lightenergy emitted each second Surface Area Temperature• Distance from the Earth

Magnitude• Stellar Brightness Apparent Magnitude (m v ) - Brightness from Earth Absolute Magnitude (M v ) - Brightness from 10 pcAbsolute magnitude depends only on a star’s luminosity (the star’s wattage)MagnitudeDifferenceBrightness Ratio(Brightness Difference)1 (2.512) 1 2.52 (2.512) 2 6.33 (2.512) 3 15.94 (2.512) 4 405 (2.512) 5 1006 (2.512) 6 251

BSpectral Classification

Absolute MagnitudeHR Diagram-10-50The SunM=+5 G2+5+10+15O B A F G K MTemperature

LuminosityClassIa & IbIIIIIIVVSizeSupergiantBright GiantGiantSub-giantDwarfThe Sun’s Spectral and Luminosity Class: G2 V

Spectral LuminosityStar m vM vType ClassAldebaran +0.9 -0.2 K5 IIIAlpha Centauri A 0.0 +4.4 G2 VAntares +0.9 -4.5 M1 ICanopus -0.7 -3.1 F0 IIFomalhaut +1.2 +2.0 A3 VRegulus +1.4 -0.6 B7 VSirius -1.4 +1.4 A1 VSpica +0.9 -3.6 B1 VWhich star appears faintest in our sky?Which star has the greatest luminosity?RegulusWhich star has the highest surface temperature?Which star is a red giant?AldebaranAntaresWhich main-sequence star has the longest lifetime?SpicaAlpha Centauri

STELLAR PARALLAX

Stellar Parallax• Motion of Earth cause parallax shifts• Used to find distance to stars out to a few hundred light-years• Parallax is ½ of measured shift• More distant stars have a smaller parallax… a star with ½ the parallaxof another star is 2x farther away• d = 1 / p “p” is in arc seconds and “d” is in parsecsEarth1 AU1 arcsec1 pc 2 pc 3 pcSun1/2 arcsec1/3 arcsecStar 1 Star 2 Star 3arcsecarcsec1 parsec 2 parsec 3 parsec5 light-years 10 light-yearsA star with a parallax of 1 arcsecond isat a distance of 1 parsec (1 pc = 3.26 ly)More distant stars havesmaller parallaxes.A star’s distance in parsecs is given by= 1where d is in parsecs and p is in arcseconds

THE PLEIADES

Stars in a Cluster•Common Properties•Distance•Age•Different Properties•Spectral Types (temperature)• Luminosity Class (size)

Star ClusterHR Diagram10 pcMain-sequenceDistance Modulus = m - MThe difference between the absolute magnitude andthe apparent magnitude can d >10 be pc used to find thedistance to a star cluster.If m-M > 0 then the distance to the cluster is > 10 pc.If m-M = 0 then the distance to the cluster is = 10 pc.If m-M < 0 then the distance to the cluster is < 10 pc.d

Cluster A: Distance 50 lyCluster B: Distance ?The apparent brightness of thestars in Cluster B are 4 timesfainter than the stars in Cluster A.What is the distance to Cluster B?Inverse-Square Law: √4 = 2Cluster B is 2 times farther or 100 ly.

AGES AND DISTANCES TO CLUSTERS

• Interstellar Dust Reddens Light (makes stars appear cooler) Dims Light (makes stars appear further away)

Pleiades - Open ClusterDistance - 380 ly Age - 60 million yearsB6 stars -- 60 million yrs.MS lifetimeage of cluster = lifetime of starsat main-sequence turnoff point

HUBBLE’S LAB

Recessional Velocity is Proportional to Distance10 Mpc 20 Mpc 30 Mpc 40 MpcMilkyWay A B C1400700V = 0 70014002100 2800km/sec40 Mpc30 Mpc20 Mpc 10 Mpc Alien’sGalaxyMilkyWay A B C10 Mpc 20 Mpc2800 2100 1400700V = 07001400km/secThe Universe is Expanding!!

Finding a Galaxy’s DistanceHubble’s LawHubble Diagramv = H o dd = v / H oTo Find Distance:Measure recessional velocity (red shift)132 Mpc

Sample Galaxies• Distance images• Recessional Velocity spectra

Hubble DiagramHubble Diagramv = H o x dxxxriseProcedure- plot data- draw best fit line- find slope (H o )xxrunslope = rise/run

ROTATION OF SATURN

Laboratory SpectrumLaboratory - No Radial motionSpectral Lines MatchEarthDistant StarRadial Velocity = 0BlueshiftRadial Velocity -RedshiftRadial Velocity + o

The Doppler Effect: Measuring the Radial Velocity of a StarLaboratory SpectrumLaboratory - No Radial motionSpectral Lines MatchEarthDistant StarvRadial Velocity = 0rΔλ λocBlueshiftRadial Velocity -Radial Velocity -RedshiftRadial Velocity +Radial Velocity + o

Important: Do not write or mark on theSaturn Handout

Spectroscope SlitLight from hereshows the largestRed ShiftLight from hereshows the largestBlue ShiftNo Doppler Shift fromthis Light

VAΔλA 2λ0VcSaturnBVΔλB 2λ0VcVcΔλλ 0Doppler o A BV c Δλ4λ 0kmsec

Top oReferenceLineBottom (mm) = Top Distance – Bottom DistanceV c Δλ4λ 0kmsecc = 300,000 km/s o = 6200 Å

Finding the Rotation Period of SaturnVPeriod = Distance / VelocityRDistance = Equatorial Circumference = 2RPeriod (P) – Rotation PeriodSaturnP = 2 R / VP2VR

THE END

1 parsec (pc) = 3.26 lyC4.2Apparent MagnitudeAbsolute Magnitude5.06.00.03.3B2.0D1.32.0ASun-26.55 pc 10 pc 15 pc

Verifying Kepler’s 2 ndEqual area in equal time.A 2A 1

Verifying Kepler’s 1stP 2L 3L 4P 1L 1L 2Centerperiluna

The AST105 Lab Exam is the week ofNovember 29 (Week after Thanksgiving).1. True2. False15