Today in Our Galaxy SECOND MID-TERM EXAM. ASTR 1040 Accel Astro: Stars & Galaxies. Another useful experience (we hope)

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1 ASTR 1040 Accel Astr: Stars & Galaxies Prf. Juri Tmre TA: Kyle Augustsn Lecture 20 Thur 20 Mar 08 zeus.clrad.edu/astr1040-tmre tmre Eagle Nebula Tday in Our Galaxy Hw t detect black hles (indirectly) Our Milky Way Galaxy in verview, seeing varius cmpnents f any spiral galaxy and a fine SONG Cnsider why spiral patterns are made in the disk f galaxies, including ur wn Examine the rtatin curve f ur galaxy, and the unseen mass (dark matter) that it implies Cmplete reading 19.2 Star-Gas Gas-Star Cycle Discuss: We are made f star stuff n Apr 1 Observatry Night 5 n Thur Apr 3, 8:30pm Anther useful experience (we hpe) SECOND MID-TERM EXAM Grade bundaries,, based n 124 pints: If 111 /124 (90%) r ver, A s [44%] 99 /124 (80%) r ver, B s [37%] 87 /124 (70%) r ver, C s [19%] Als +, plain, and within these ranges RESULTS FROM SECOND MID-TERM EXAM G thrugh answer sheet and talk t us if d nt understand ur chices. Keep exam + answers fr future review (cmp final) Hw t detect a black hle Observing a black hle: Cygnus X-1 1

2 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 SS 433 tp candidate fr wild bject! SS 443 BH + jets anther stellar-size size black hle 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 Luminsity ~ 10 6 t 10 3 times utput frm galaxy Visible frm acrss the universe! HYPERNOVA? Cllapse f very massive star > BH HST 2

3 Nw t Our Milky Way Galaxy The Milky Way (fuzzy ribbn f light acrss the sky) Size f Milky Way If we might see Milky Way frm utside billin stars 100,000 light years in diameter,, r ~ 30,000 pc = 30 Kpc (kil-parsecs) Sun is lcated abut 8.5 kpc frm center, in the `Orin Arm Spiral Sb galaxy NGC 4414 Artist s s sketch! Milky Way Anatmy: Spiral Galaxy Disk: includes spiral arms -- yung, new star frmatin Bulge & Hal: lder stars, glbular clusters 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)? D. 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 3

4 Disk is very thin! Disk is very thin! Artist s s edge-n view 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 Stars and gas are all mving! Sing ur way t the Milky Way THE GALAXY -- LIGHTEN UP THIS INSPIRES A SONG! 4

5 Pre-Milky Way: early hal + disk Hw t build a spiral galaxy (r s we think!) 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. 5

6 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 Different star mtins in disk & hal 1. Stars mving in circles: rbital velcity law = R x V 2 / G M R mass inward radius rbital velcity faster rbit, mre mass slar system 2. MW rtatin curve Reality fr the Milky Way Rtatin curve is flat r even rising! Mst f the mass f the galaxy is utside the slar circle! Rle f dark matter n rtatin prfile DARK MATTER But few stars, little gas there DARK MATTER! prbably in large hal -- utweights stars+gas by factr f 3 t 10 6

7 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) 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? ) Magnificent spiral galaxy M51 Whirlpl Why the tw-armed SPIRAL PATTERN? 7