Elementary Astronomy PSC 203
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The Calendar days seasons and the moon PSC 203 Day and Night I What causes the pattern of clay and night I The earth39s rotation Solar verse Sidereal I Solar gt sun Sidereal gt stars I Sidereal clay I time for a star to move from overhead once around and back to overhead I 23 hours 56 minutes I Difference caused by orbit around sun Overview I In this section I How is a day defined astronomically I What causes the seasons of the year I How does the moon phase tell time I If time eclipses Solar Day I Definition I Time to rotate once around on axis I Measured from noon to noon I Varies a little bit from day to day I Average is 24 hours Solar Year I Definition I Time to revolve once around Sun I Full orbital path I 3652422 days I Need for leap years More on the day and year In p anemnum lhuw the skv Hams m Una dav mew the skv changes we the veav Seasans Cause of the seasons quotWe mtofme eanh on 5 axis re anve to me sun 23 5 degees Mammms dwecuon over me year msuax egtlta mp e Nm rot mm wmnmm Ana wma 5mm 4w M n mm a s 4w quotrm Y x re m mm M r e 7 es News Seasons vs hemisphers Northern and southern nemrspnere have reversed seasons Phases of me Moon Seasons In mmmer me am rs ata srnaue ang e more effecuve neanng In Wmter me am rs at a arger mg e ess effecuve hEDng More on Sasons In one pranerarorn We wru ook athcw me mghtskychanges ve me var How one Sun s posmon chmges The Eorpue Equmox and So snoe Phass The appearanoe oranges 39 Amunt Bf Hum natmn 39 LDEEUDH Bf Hum natmn What are me pnases7 WaxingCiescent WaningGmbuus 39 FirstOuarler Last Quarter Waxing Gibbous Wanlng Crescent Waxing verses Waning I Waxing means illuminated i5 increasing I Waning means illuminated i5 decreasing Relative Positions Phases I Name I Wu illuminated New I 0 Wu illuminated I Crescent I 050 Wu illuminated I Larter I SO Wu illuminated I Gibbous I 50100 Wu illuminated I Full I 100 Wu illuminated This month39s phases rename More on the Moon I In the Planetarium I We will look at phases on sky I Relative positions of sun and moon for each phase I How to tell time with the moon Solar eclipse De nmon Eclipss The shadow orme moon falls on me Earm Eclipse as sen from space As seen from Earth Nhnn blocks cut sun Solar eclipse Solar Eclipse Geamezy vWere does lhe moon need m be compared to me earlh a a su for a solar edlpse to happenv drawing and phase Moon is beMeen Sun and Earth Possible at new moon phase Solar eclipse types I Total solar eclipse I Moon completer blocks Sun I Partial solar eclipse I ks part of Sun I Annular solar eclipse I Moon blocks center but not edge Lunar Eclipse I De nition I Shadow of the earth falls on the moon I Total lunar eclipse I m on entirely in Earth39s shadow I Partial lunar eclipse I moon partially in Earth39s shadow Lunar eclipse sual Examples quot l O Lunar Eclipse Geometry I Where does the moon need to be compared to the earth and sun for a lunar eclipse to happen drawing and phase I Moon is behind earth compared to sun I Full moon phase More on Eclipses I In planetarium I We will see how Sun and Moon pass each 0 her on sky I In later lecture I W en and where eclipses will be visible PSC 203 7 Elementary Astronomy Name Spring 2008 Prelecture Assignment Due February 21 Reading Assignment textbook sections 62 63 64 65 1 What is the ecliptic 2 Fill in the blanks with the appropriate month The equinoxes occur in and The solstices occur in and 3 The Earth s aXis is tilted at an angle of degrees 4 What month of the year is the Earth closest to the Sun 5 At noon in summer the sun is A very high in the sky compared to winter B very low in the sky compared to winter C directly overhead just like in winter Other announcements 0 Wednesday evening lunar eclipse activity on campus runs from 8301000 don t forget to complete your outside activity on the eclipse Thursday Feb 21st we will meet in the planetarium at 930am 0 o o 0 Bring your lecture tutorial book to the planetarium Galaxies PSC 203 Number of galaxies I Just how many galaxies are there I Hubble Deep field gives us a clue Overview I In this lecture I How many galaxies are there I What types of galaxies are there I What are the features of each type Hubble Deep field I Based on the counts of two deep field pictures that have been taken I Estimated galaxy count I Over 100 billion galaxies Galaxy types I How might we categorize galaxies I what properties could be used to classify galaxies I Size I Shape I Brightness Hubble s classi cation I Hubble came up with a classification based on I Shape I What were his groupings I Spiral I Elliptical I Irregular Spiral Galaxies I Definition I a galaxy with a disk in which its bright stars form a spiral pattern I What galaxy have we already seen that is a spiral Example Image www I 39 Q Example Image Structure I same general structure as our galaxy I diSk I bulge I halo I spiral arms Two types of spirals I Regular spirals I Barred Spirals Sizes Viewing Angle I they range somewhat in size I spiral galaxies look very different I Milky Way is depending on the angle of the disk 75000 ly across I face on see top view whole disk I smaller I edge on see side view edge of disk I 15000 ly across I larger I 112500 ly across Face On Exam Ie Edge On Example Tilted Exam le Elliptical Galaxies I Definition a galaxy in which the stars smoothly fill an ellipsoidal volume ellipse flattened circle I ellipsoidal volume flattened sphere Structure I dense central core I lower density halo SIze I ranges greatly I smallest I 750 ly across I largest I 375000 ly across Appearance I specks in halo are not stars but entire globular clusters mg Example Images Example Images Irregular Galaxies Structure De nition n can take many forms key is irregularity and asymmetry a galaxy lacking a symmetric structure Example Images Example Images Irregulars Interacting Galaxies I irregulars may look like nebula some irregulars form when galaxies but they are really much much larger interaCt I And much much further away I QFaVitY 0f one PUHS 0 the Other I may even collide end result is galaxy or galaxies with distortions Example Images m E Collisions InClass Activity I When galaxies collide what happens to the I describe the main features of each galaxy stars type I They may change positions ISPiral I The stars themselves do not generally lelliptical collide with other stars Iirregular The spacing is too far apart Observing Other OverVIew I In Ms 52 on was 5 Stars H WWW mama H 5 may How an m ma we mass We 5mm PSC 203 How do w dasswy yam 5 Stars rs lwmnvu ucxatag d39E tare they Masswe gas bodes m space Generates hgwt m fuswm De um Jsmrs 10 vs mm the samev ned m fuswm at the m2 Properties of Stars mm mnat prwernes m stars can we measue Brawscmmng or use m desmbe the star u maung In grmps m 23 Wrth down as many mms as We can d39mk one answer Wratprmem es ufshars can We measue or use to nesmbe the snarsv Hope tles of Stars me me we W W at eeda 2nd bng nexx Color edempemde 2ndme Next m e em 2nd 2 03k OJIOr what edges eddy vanahan m 515157 Yhe m m dr 5 stay mmcates m5 ve ahve mm we aheady studxed m m hqht mzvevatuve e We stavs ave hattev man 12 stays Yempevahue m Spech39a of 5m hth d Sthulmn we 5 wave e qths s 5 ve ahsawtmn spectvum speeme hnes depend an nmvmhonzrdkmveulure Can he used m ednmm temvevatuve EXDnw0 Brightness Wm do aH stars not have the same bnghmessv I 2 factors Drstance Lurmnosrty Measuring Distance I Severa methods I ParaHax I Standard cand eS Bri ghtness Distance Stars are drfferent drstances awav from our so ar svstem These drstances are verv arge 39 dosest star Droxrrna Centarr 4 24 w Parallax Mmrexpenment I Apparent shrft of a Star re atwe to the ba k d serve c groun e toob r5 motron ce Na wt verv arge drstance Dlstance m brig39vmess the avvavent huqmness D a ham decveases nvestW as the Squave af 5 dxstante Lumlmslty ummaswr the amaunt af enEVqY adY vadxated Dev semnd w a n umts my ummm 1 L Lumlmslty my ahYects vadxate 255 enEVqY temvevatuve atsuvfa2natca125 what m anew Lum mswty why da stays have dxffevent ummasmesv deven 5 an hemvevatuve a depends an m Lum ms ty depends an sue Mme 5125 an avqev ahyects umts D m R my vadmsquot Luminosity Formula L turnrnosrty 2 4 L 472R 07quot I R radrus T temperature 39 R2gt 4 1 39 T2 rgt16L I named after 2 astronomers Hertzsprurrg I RLsseH They Wanted to nd reratrmsnrps to understand tne star proper res a grapn of star propertres re atwng tnerr temperature and dmrnosrty Emmi Enner temperature or co or o ICw est Reddest at ngnt The HR Diagram the amount of energv radrated per Second b a Star I P otted m vertwca am Brrgrtestat mp Drmmest at bottom Understanding the diagram I Stars are not randomly distributed I Most fall in one group across the middle I Some fall above or below Main sguence I the region in the HR diagram in which most stars are located I Stretches from upper left to lower right I These are the normal stars Radius relationship I for any temperature can 3 luminosities I Normal High or Low I Luminosity depends on temp and size I They must have different sizes llarge radius high luminosity Imedium radius normal luminosity Ismall radius low luminosity For comparison I Consider the typical height verses weight diagram I Divides into I normal I Overweight I Underweight IiiMushy li rlur Un r sl Unrrllriri39ll39l ISnlar L 39l mil Spectral Chg D x Iu5 as 3 spa IIE 10quot 3 t I I II x 0039339 While wnrfs mono 2303 menu 5303 3343 Tenpualufe Retain l I I at NEG EEI IEI llIIEICI Empnrnhlrn Kczhin Size classi cations Giants TWO new goupg stars of arge radrue and thus arge urmn at Gram a arger than norma 39 Red 9mm gt 600 9W Dwarfs a smaHer than norma 39 We 9 6 gt hot 9 5quot swergrants rgt verv arge radrue and umtnosttv for the temperature warrcznm39r mt vn 5m Inna 39remwxemf 39 apartment mumsquot r m x wequot mm wanaw stars of verv smaH radree and thus ow umtnosttv Whrte dwarfs rgt very hot dwarfs etm arm and ow umrnoerty Red dwarfs rgt coo dwarfs x mm vax m me am 13 e Wm was man atun rzmwmlmmm ww mum MEN gm 7 WW I Draw and abe the baswc HR dwagram I Where mm a norma star be7 Dwscuss vour answers m groups of 273 Overview I In this lecture I What types of galaxies are there I What are the features of each type PSC 203 Galaxy types Hubble s classification I How might we categorize galaxies I Hubble came up with a classification based I what properties could be used to classify onu galaxies 39 Shape I Size I What were his groupings I Shape I Spiral Barred Spiral I Brightness I Elliptical I I Irregular Peculiar Galaxy types ir i I Definition I a galaxy with a disk in which its bright stars form a spiral pattern I What galaxy have we already seen that is a spiral I ficleo galaxy type overview 39 Atleo Z fainter galala Example Image Example Image Stmcture Two types of spirals same genera suucmre as ou ga axy Regubv suva s Eaned Sam s a bu ge ha o spra arms mewange somewhatm sue spwra ga axles We very afferent WW WWS dependng on me ang e o he dsk 75 u w amass face on see mp Mew Who e dxsk smaHer edge m see we mew edge Ofdsk 15mm w amass arger 112mm w muss I De nmon a ga axv rn Much tne stars smoo 39 v nu an eurpeordat votume eurpee attened crcte eurpeordat votume attened sphere IZE densa cemm care ranges great v lower density ha o smaHest 750 w across argest 375000 w across Appearance I specks in halo are not stars but entire globular clusters Example Images Irregular Galaxies 39 De nition l a galaxy lacking a symmelric structure Example Images Structure 39 can take many forms I key is irregularity and asymmetry 25 Irrgulars I irregulars may m like nebula I but they are really much much larger 27 Interacting Galaxies I some irregulars form when galaxies interact I gravity of one pulls on the other I may even collide I end result is galaxy or galaxies with distortions 29 Example Images Example Images 30 Example Images Collisions InClass Activiy describe me main features of each galaxy type spiral elliptical irregular I We will look at this next lecture PSC 203 7 Elementary Astronomy Name Spring 2008 Prelecture Assignment Due February 26 Reading Assignment textbook sections 321323 332334 also look at gure 326 1 What object in the solar system has the most mass and the largest size 2 Which planet has a larger tilt angle Jupiter or Saturn 3 The Sun is mostly composed of two elements and 4 What is the Solar Nebula Theory 5 Ice was able to condense in which of the following two locations in the solar system the inner region the outer region Other announcements 0 Complete the lecture tutorial on Seasons p9l96 as Homework 0 Bring the tutorial book on Tuesday prepared to turn in the recent work you should have completed pg 34 pg 7981 pg 1315 pg 9196 0 Tuesday we meet in the normal classroom in Hodge Hall I will get you the reVised lecture exam and reading assignment schedule on Tuesday 0 Overview Local Galaxies and I In this lecture Collisions of Galaxies 39 Nearby Qa39ax39es I Interactions of gaIaXIes PSC 203 Review Galliumt Types I What galaxy do we live in I What type of galaxy is ours I What are the other types of galaxies Nearby Galaxies I Closest galaxy I Sagittarius dwarf I Dwarf elliptical I Other very close galaxies I Large and Small Magellanic clouds I Irregular galaxies Large Magellanic cloud Sagittarius Dwarf Galaxy I Hard to see I Fairly faint I Spread out on sky I Other stars in front Small Magellanic cloud local subgroup I What types of galaxies are in local sub group I Us a spiral I Mostly dwarf ellipticals I Some irregulars LosaLGmup Andromeda I The full local group is larger still V I V39 I about 3040 galaxies I about 1 Mpc across I biggest I Andromeda galaxy I y axes fthe gm Interacting Galaxies I Definition I Galaxies which are close enough for their mutual gravity to affect each other In r in Ixi Collision Overview I some irregulars form when galaxies Gas and dust affected most lnteraCt I Pulled away into strange shapes 39 graVltY 0f one PUllS on the Other I New star formation triggered I may even C0llide I Stars may be deflected I ileo what happens when galaxies I Move to different location in galaxy I end result is galaxy or galaxies with I May be flung out and separate from galaxy dlStOI tlons I Stars themselves don39t collide Simulations I Simulations o zen used to predict interactions lummlpc y l or I Simulations match well in observations 41 Galaxy mergers I Very large galaxies may be due to mergers of many snaller galaxies eo rleo a I Slow and gradual process Interactions in the Local Group Milky Way and Andromeda I SagittariLs dwarf galaxy I And39omeda has interacted with ils Already collided Wiin Milky Way and emerged neighbors from the other Side at least once probably Milky Way and Andromeda will eventually more tlmes interact cl o zi lEEl lLl l cl I a m d in I other dwarf galaxies Evidence of other dwarf galaxies already merged Wllh Milky Way Recent evidence I Used to think that Andromeda is much larger than us I Andromeda and Milky Way close to same size I Will collide a bit earlier I Maybe 3 billion years from now PSC 203 7 Elementary Astronomy Name Spring 2008 Prelecture Assignment Due March 20 Reading Assignment textbook sections 211 221226 1 Light travels through empty space at a speed of 2 Which of the following properties of light is measured in units of Hertz a speed b wavelength c frequency d energy For the following questions the bands of light are Infrared Gamma rays Radio wavesUltraviolet Visible X rays 3 List the bands of light in the correct order from small wavelengths to large wavelengths 4 List the bands of light in the correct order from low energy to high energy 5 Which band of light includes microwaves Other announcements 0 Work on your WAC rewrite see rewrite instruction sheet 0 Remember to bring your tutorial book if you didn t have it with you in class today Your next outside activity will be handed out in class on Thursday See me for any concerns or questions about your midterm grades Not all work was included in the midterm grade calculation so your grade may have shifted some already 00