3/22/18. Onward to Galaxies, starting with our own! Warping of Space by Gravity. Three aspects of falling into a black hole: 1) Spaghettified

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1 ASTR 1040: Stars & Galaxies Prf. Juri Tmre TAs: Peri Jhnsn, Ryan Hrtn Lecture 20 Thur 22 Mar 2018 zeus.clrad.edu/astr1040-tmre M51 Whirlpl Onward t Galaxies, starting with ur wn! Revisit Our Milky Way Galaxy in verview, aspects f any spiral galaxy Hw spiral galaxy may have been assembled Examine galaxy cmpnents: stars, gas, dust Lk at why spiral patterns are made in the disk f galaxies, including ur wn Hmewrk #9 due tday, new HW #10 ut requires reading S2 n special relativity Read Chap 19 Our Galaxy in detail Warping f Space by Gravity Gravity impses curvature n space light s path thrugh space will be bent by gravity within the event hrizn, it cannt climb ut f the hle As matter appraches event hrizn tidal frces are tremendus bject wuld be spaghettified Three aspects f falling int a black hle: 1) Spaghettified As matter appraches the singularity tidal frces (difference between gravitatinal frce at tw pints) are tremendus Yur feet wuld feel a much strnger pull f gravity than yur head bject wuld be spaghettified REVISIT 5 Three aspects f falling int a black hle: 2) Gravitatinal Redshift Frm mthership's view As the prbe gets clser and clser t the event hrizn, the light becmes mre and mre redshifted Phtns lse energy climbing ut f the black hle gravity well At the EH (frm ur view), phtns are redshifted ut f existence (zer energy) Frm prbe's view: Outside wrld gets blueshifted Phtns gain energy falling int the black hle gravity well 6 Three aspects f falling int a black hle: 3) Time Dilatin Frm mthership's view As the prbe gets clser and clser t the event hrizn, its clck appears t slw dwn The prbe (and clck) never get t the event hrizn It mves slwer and slwer, eventually freezing at the EH Frm prbe's view: it heads straight int the black hle Nthing special at the event hrizn Outside wrld clck appears t be sped up 1

2 Black Hles Dn't SUCK! Black hles have gravity, just like nrmal stars, planets etc. The nly prblem is that yu can get SO clse t the cncentrated gravity near a black hle that yu can't get ut again Hw t detect a black hle Observing a black hle: Cygnus Lp SNR Hme f Cyg X-1 Cygnus X-1 Cygnus X-1: Blue supergiant (strng winds) purs H + He nt accretin disk f black hle Stellar-size black hle Views f Veil Nebula Accretin disk Such SNR may have a BH lurking!.. but nt this ne Blue supergiant 2

3 SS 433 tp candidate fr wild bject! SS 443 BH + jets anther stellar-size black hle Gamma-Ray Bursts HYPERNOVA? Cllapse f very massive star > BH Luminsity ~ 10 6 t 10 3 times utput frm galaxy Visible frm acrss the universe! HST Review 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 OVERVIEW REVISIT Our Milky Way Galaxy 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 Artist s sketch! 3

4 If we might see Milky Way frm utside One-pager: ALL abut us! Edge-n Sketch f Milky Way Spiral Sb galaxy NGC 4414 Tp Milky Way Anatmy: Spiral Galaxy The Milky Way (fuzzy ribbn f light acrss the sky) Disk: includes spiral arms -yung, new star frmatin Bulge & Hal: lder stars, glbular clusters We might prefer t lk like this! Prettier? 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 D. M101 with mre distinctive spiral arms C. Gas and dust can absrb light, making distance estimates uncertain D. All f the abve 4

5 Cmpsite f M101 much ges n! Disk is very thin! (relatively speaking) Artist's sketch Pre-Milky Way: early hal + disk Galaxy NGC 4565 à nearly edge-n REAL IMAGE! What are galaxies made f? Hw t build a spiral galaxy (r s we think!) M104 Smbrer Galaxy 5

6 Inventry f stuff making up ur galaxy + dark matter Stars Gas Dust Clicker Pll f Advice Hw d yu take ntes (r listen) during lectures? A. I get mst f it by just listening B. I write dwn sme ntes, then g back t bk t lk things up C. I listen, take sme ntes, then get cpies f lecture slides frm curse website D. I enjy talking with my buddies, and they tell me later if I missed anything E. I try t read the subject in advance, and then listen, taking sme ntes in class All spiral galaxies are cnstantly changing Cycle f The starà Star-Gas- gas Star àcycle star 6