Making and Using the Hertzsprung - Russell Diagram

Transcription

1 Making and Using th Hrtzsprung - Russll Diagram Nam In astronomy th Hrtzsprung-Russll Diagram is on of th main ways that w organiz data dscribing how stars volv, ags of star clustrs, masss of stars tc. To hlp you undrstand th diagram, you will b making your own. At th back of this writ up, you will find a blank form for th Hrtzsprung-Russll Diagram. Th Hrtzsprung-Russll diagram plots tmpratur vs brightnss for stars You will b complting th scals for th axs, plotting th closst and th apparntly brightst stars, and idntifying th luminosity classs for stars. 1) Labl th coordinats on th Hrtzsprung Russll diagrams. Thr ar TWO scals for th ordinat (x coordinat) and TWO for th ordinat (y coordinat). Th abscissa (x axis) gts both tmpratur and spctral typ, whil th ordinat (y axis) gts both luminosity and magnitud. Your scal is st up to hav th tmpratur on th bottom with highr tmpraturs to th lft (opposit th usual). Th tmpratur scal is LOGARITHMIC. Equal amounts of spac rprsnt qual powrs of 10. This layout is traditional, as you can s if you look at th tmpratur axis for th plots in chaptr 17. To st up this scal, us 10,000K nar th middl whr it is markd. Th nxt vrtical lin to th LEFT is 20,000K. Th nxt vrtical lin to th RIGHT (vry clos by) is 9000K. Each vrtical lin going to th right is 1000K lss. Th scal dos not go down to zro or vn to 1000K bcaus thr ar no stars of that tmpratur. Labl th spctral typs corrsponding to various tmpraturs across th top. Th data rlating spctral typ and tmpratur (for th Main Squnc) is givn blow. Us it to dcid whr to plac th spctral typs. A spctral typ has a lttr and an Arabic numbr (th normal kind). Th lttrs go in th squnc OBAFGKM going from hottr to coldr and a numbr. Th numbrs indicat surfac tmpraturs as wll, thy just provid a finr subdivision than do th lttr. So from hottst to coldst, th spctral typs would b O0, O1, O2, O3, O4, O5, O6, O7, O8, O9, B0, B1, B2, B3, B4, B5, B6, B7, B8, B9, A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, F0, F1, F2, F3, F4, F5, F6, F7, F8, F9, G0, G1, G2, G3, G4, G5, G6, G7, G8, G9, K0, K1, K2, K3,K4, K5, K6, K7, K8, K9, M0, M1, M2, M3, M4, M5, M6, M7, M8. No doubt you hav th pictur. Evn coolr, stars hav bn found. Thy ar typs L and T and hav surfac tmpraturs that go blow 3000K. As you labl th axs, you will only b abl to labl points corrsponding to th spctral typs givn in th first tabl blow. Th brightnss, in units of th luminosity, gos on th lft vrtical scal and and magnituds go on th right. Th scal is orintd so that brightr stars ar toward th top. Each horizontal lin corrsponds to 10 tims highr luminosity. Labl th luminosity on th lft. Us powrs of 10 tims th luminosity of th Sun (g10 3 L for 1000 tims th Sun s luminosity) Th right hand vrtical scal is magnituds. Th brightr th star, th LOWER th magnitud. Each small lin is on magnitud diffrnc. Labl all th magnituds. Th Sun is at about magnitud 4.83, so th lin for1 L is not quit lind up with th magnitud marks. How can thr b two coordinat labls for on axis? Bcaus thy ar two diffrnt ways of tlling th sam information. Spctral typ basically tlls th surfac tmpratur. Magnitud and luminosity both masur brightnss. If you hav vn th smallst qustion of whthr your scals ar corrct, lt m chck thm bfor you plot th star positions. 2) Th Hrtzsprung -Russll (HR) diagram can b usd to stablish rlationships btwn th physical proprtis of stars. In ordr for you to do this, you will b plotting th data for th stars attachd on your HR diagram. Hrtzsprung Russll Diagram HW 1

2 Stars brightnss can b xprssd ithr in apparnt magnitud (m) or absolut magnitud(m). Apparnt magnitud tlls how bright th star appars, including th ffcts of its distanc. Absolut magnitud tlls how bright th star would appar if it wr at 10 parscs, xcluding th varying distancs of th star will not affct how thy compar to on anothr. Sinc w want to undrstand th proprtis of th stars thmslvs, w us th absolut magnituds. Data for th 32 apparntly brightst stars and th 20 closst stars is attachd. Plot th spctral typs and absolut magnituds for both sts of stars. Us on color for th brightst stars and a diffrnt color for th closst stars. Numbr th points, so that you can kp track of which dot corrsponds to which star. 3) Sktch in th main squnc. You may b abl to do this basd on th data you hav plottd. If th main squnc is not apparnt from th data, us th points from th tabl blow and connct thm with a smooth curv. (Us a diffrnt color or symbol to sparat ths thortical points from th obsrvational ons you hav alrady plottd). Your txtbook has 4) Sktch in th curvs for luminosity classs, I, III, and V. Figur in your txt boo shows ths curvs. 5) Dcid on th luminosity class for ach of your stars. Your choics ar II, III, IV, V, and I. Mak th choic basd on which of th luminosity class curvs th star is closst to. Do mak a dcision for ach star. Don t worry about doing a prfct job in th rgion of O, A, and B stars whr th luminosity classs ar vry clos togthr. Th whit dwarfs don t gt a Roman Numral. Just call thm wd in th tabl. Th ida is to fl how this all works, so don t go to look up \th stars on by on to gt it prfct. Main Star Squnc Proprtis Us to Rlat Tmpratur and Spctral Typ on Axis Spctral Typ Surfac Tmpratur 0 K M v, Absolut Visual Magnitud Luminosi ty numbr of tims Wavlng th pak mission nm Mass, numbr of tims Radius, numbr of tims Avrag Dnsity, gm/cm , , B0 28, , B5 15, A A F F G G K K M M M Hrtzsprung Russll Diagram HW 2

3 CLOSEST STARS # Nam M v, m v,, Spctral Distanc Luminosity 1 Sun G2 2 a Cnturi A G a Cnturi B K Barnard s Star M Wolf M Laland M Sirius A A Sirius B whit dwarf Luytn 726-8A M Luytn M Ross M Ross M Eridani K Luytn M Ross M Cygni A K Cygni B K Indi K Procyon A F Procyon B whit dwarf S2398 A M S2398 B M Groombridg 34 A M Groombridg 34 B M Lacaill M t Cti G BD M L M Lacaill M Kaptyn s Star M Krugr 60 A M Krugr 60 B M Whit dwarfs- assum that thy hav surfac tmpratur 10,000K Hrtzsprung Russll Diagram HW 3

4 BRIGHTEST STARS as sn from Earth # Nam M v, Absolut Magnitud m v, Apparnt Visual Magnitud Spctral Typ Distanc (ly) 7 α Canis Sirius A Majoris 33 α Carina Canopus F0 454 Luminosity Class 34 α Bootis Arcturus K α Cntauri Rigil G A Kntaurus 35 α Lyra Vga A α Auriga Caplla G β Orionis A Rigl B α Canis Procyon F Minoris A 39 α Eridanii Achrnar B α Orionis Btlgus M β Cntari Hadar B1 327 AB 42 α Aquila Altair A α Tauri A Aldbaran K α Scorpii A Antars M α Virginis Spica B β Pollux K Gminorum 47 α Piscis Fomalhaut A Austrinis 48 α Cygni Dnb A β Crucis Bta Crucis B α Crucis Acrux B Hrtzsprung Russll Diagram HW 4

5 Hrtzsprung Russll Diagram Spct ral Typ 1L 5 0 M a g n i t u d 10-2 L Tmpratur Hrtzsprung Russll Diagram HW 5