Today. Today in Milky Way. ASTR 1040 Accel Astro: Stars & Galaxies

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1 ASTR 1040 Accel Astr: Stars & Galaxies Prf. Juri Tmre TA: Nichlas Nelsn Lecture 19 Tues 15 Mar 2011 zeus.clrad.edu/astr1040-tmre tmre Superbubble NGC 3079 Tday in Milky Way Lk at cmpnents f galaxy: stars, gas, dust Examine the rtatin curve f ur galaxy, and the unseen mass (dark matter) that it implies Lk at why spiral patterns are made in the disk f galaxies, including ur wn Examine the Star-Gas Gas-Star Cycles wrking in ur galaxy disk, and its ingredients Interstellar Medium (ISM) gas and dust, plus super-bubbles blwn by multiple supernvae Recycling n a grand scale, and building the heavier atms Tday Hmewrk Set # 8.5 passed ut tday, HW # 8 due Cmplete yur reading f 19.4 Mysterius Galactic Center Remember that Planet Finder prject is due this Thur Graded Mid-Term Exam 2 will be returned n Thur Observing a black hle: Cygnus X-1 Cygnus Lp SNR Hme f Cyg X-1 Cygnus X-1: X Blue supergiant (strng winds) purs H + He nt accretin disk f black hle Stellar-size black hle Accretin disk Blue supergiant 1

2 Views f Veil Nebula SS 433 tp candidate fr wild bject! Such SNR may have a BH lurking!.. but nt this ne anther stellar-size size black hle SS 443 BH + jets Clicker Size f Black Hle What des the Schwarzschild radius f a black hle (BH) depend n? C. A. Bth mass and chemical cmpsitin f the BH B. Radius f BH, as measured by careful bservatins f its size C. Only the mass f BH D. Whether BH frmed in massive star supernva r in sme ther way Gamma-Ray Bursts HYPERNOVA? Cllapse f very massive star > BH Nw t Our Milky Way Galaxy Luminsity ~ 10 6 t 10 3 times utput frm galaxy Visible frm acrss the universe! HST 2

3 The Milky Way (fuzzy ribbn f light acrss the sky) billin stars 100,000 light years in diameter,, r ~ 30,000 pc = 30 Kpc (kil-parsecs) Size f Milky Way REMINDER Sun is lcated abut 8.5 kpc frm center, in the `Orin Arm Artist s s sketch! If we might see Milky Way frm utside We might prefer t lk like this! Prettier? Spiral Sb galaxy NGC 4414 M101 with mre distinctive spiral arms Cmpsite f M101 much ges n! Milky Way Anatmy: Spiral Galaxy Disk: includes spiral arms -- yung, new star frmatin Bulge & Hal: lder stars, glbular clusters 3

4 Clicker Where are we? Why was it s difficult t figure ut where in the Milky Way are the Sun and Earth lcated, and if urs is the nly nebula (galaxy)? A. We are immersed in a sup f stars, gas and dust, s hard t see far B. In a middle f city f stars, hard t figure shape f verall `metrplitan area C. Gas and dust can absrb light, making distance estimates uncertain D. All f the abve D. Disk is very thin! Artist s s edge-n view Spiral galaxy NGC 891 nearly edge-n One-pager: ALL abut us! Sketch f Milky Way Edge-n stars, gas, dust in disk Tp Pre-Milky Way: early hal + disk Hw t build a spiral galaxy (r s we think!) 4

5 All spiral galaxies are cnstantly changing Inventry f stuff making up ur galaxy Stars Gas Cycle f star gas The Star-Gas- star Star Cycle + dark matter Dust Many views f ur galaxy disk Reading clicker mapping ur galaxy We want t map the structures f very cld gas within the dusty disk f the Milky Way. What wavelengths shuld we be using, and why? A. radi B. visible light C. x-rays A. A. Radi Dust bscures ur visin f much f the galaxy in visible and UV light. X-rays nly highlight the httest and weirdest places 21 cm radi waves map nrmal hydrgen gas -- these pass thrugh dust unaffected cnfused visible image MW disk in radi Hal & bulge: swarming in and ut Disk: circular + bit up/dwn Mtin f stars in spiral galaxy 5

6 Different star mtins in disk & hal 1. Stars mving in circles: rbital velcity law = R x V 2 / G M R mass inward slar system radius rbital velcity faster rbit, mre mass 2. MW rtatin curve Massive dark matter hal fr MW Stars and gas are embedded in a much larger dark matter hal?? Dn t t knw what dark matter is yet prbably nt barynic (usual prtns, neutrns, electrns) Rtatin curve is flat r even rising! Mst f the mass f the galaxy is utside the slar circle! But few stars, little gas there DARK MATTER! prbably in large hal -- utweights stars+gas by factr f 3 t 10 Reality fr the Milky Way Rle f dark matter n rtatin prfile DARK MATTER Dark matter hal fr galaxies Presence revealed by rtatin curves (mtins f stars in galaxy) Dark matter extends beynd visible part f the galaxy -- mass is ~10x stars and gas! Mst likely subatmic particles, as yet unidentified (weakly( interacting massive particles WIMPs? ) 6

7 Discussin Tpic Cycle f Stars and Gas -- Des this cntinue frever in Milky Way why r why nt? And des it depend n yur lcatin within MW? Why spiral arms? Density waves stars mve in and ut f denser regins Mre like ripples in a pnd than arms f a pinwheel In dense regins, star frmatin is mre intense,, s arms are brighter M51 - Whirlpl Push and pull f gravity in disk Gas/stars are pulled a little frward r backward tward the high density regins Such clumping helps create a spiral pattern 7