ASTR 1040: Stars & Galaxies

Transcription

1 ASTR 1040: Stars & Galaxies Onward t Galaxies, starting with ur wn! M51 Whirlpl Prf. Juri Tmre TA: Ryan Orvedahl Lecture 21 Tues 1 Apr Our Milky Way Galaxy in verview, aspects f any spiral galaxy and a fine SONG 6 Examine galaxy cmpnents: stars, gas, dust 6 Lk at why spiral patterns are made in the disk f galaxies, including ur wn 6 Hmewrk #9 due tday, new HW #10 ut 6 Read Chap 19 Our Galaxy in detail 6 Observatry Night #7 this Wed (signup) 6 Slar Day (ptinal) this Thur 2-4pm zeus.clrad.edu/astr1040-tmre Review Clicker Size f Black Hle 6 What des the Schwarzschild radius f a black hle (BH) depend n? C. 6 A. Bth mass and chemical cmpsitin f the BH 6 B. Radius f BH, as measured by careful bservatins f its size 6 C. Only the mass f BH 6 D. Whether BH frmed in massive star supernva r in sme ther way Our Milky Way Galaxy OVERVIEW billin stars 6 100,000 light years in diameter, r ~ 30,000 pc = 30 kpc (kil-parsecs) 6 Sun is lcated abut 8.5 kpc frm center, in the `Orin Arm Our Milky Way Galaxy Artist s sketch! Stars and gas are all mving! THIS INSPIRES A SONG! 1

2 4/1/14 Sing ur way t the Milky Way THE GALAXY -- LIGHTEN UP 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 Disk: includes spiral arms -- yung, new star frmatin The Milky Way (fuzzy ribbn f light acrss the sky) Bulge & Hal: lder stars, glbular clusters 2

3 We might prefer t lk like this! Prettier? Clicker Where are we? 6 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)? 6 A. We are immersed in a sup f stars, gas and dust, s hard t see far 6 B. In a middle f city f stars, hard t figure M101 with mre distinctive spiral arms D. shape f verall `metrplitan area 6 C. Gas and dust can absrb light, making distance estimates uncertain 6 D. All f the abve 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! 3

4 4/1/14 Hw t build a spiral galaxy (r s we think!) Inventry f stuff making up ur galaxy Stars Gas + dark matter Dust What are galaxies made f? All spiral galaxies are cnstantly changing M104 Smbrer Galaxy Cycle f starà gas The Star-Gas- à star Star Cycle Cld Stuff Dark Mlecular cluds (10 s f Kelvin) Hrsehead in clse-up Gas & Dust Heated by stars t 100s-1000s Kelvin Absrbs visible and UV light Transparent t lnger wavelengths Infrared, radi Warm Stuff Emits its wn infrared light Hrsehead Nebula 4

5 Trifid Nebula (M20) Ht Stuff visible Spitzer infrared 6 Inizatin nebulae 6 Ht (yung) stars inize hydrgen and ther elements in the gas 6 T~ 10,000 K near ht yung stars Trifid Nebula Where the emissin clrs cme frm.. Emissin nebulae O & B star assciatins 6 Emissin lines frm hydrgen and ther inized elements 6 T~ 10,000 K near ht yung stars Lagn Really Ht Stuff Fast electrns & magnetic fields REALLY HOT STUFF 6 Bubbles f ht gas blwn ut by SUPERNOVAE 6 T = millins f degrees K 6 Synchrtrn emissin frm SNR 6 X-ray and radi 6 Mixing with rest f galactic gas à enrichment with heavy elements 6 Traces very ht gas bubbles (SNR) 29 Chandra X-ray image f Tych Brahe 1572 supernva remnant 5

6 Super-bubbles Super-bubbles in spiral galaxy NGC When multiple bubbles jin (frm a cluster) they can create superbubbles. 6 If the superbubbles reaches the edge f the disk, it can blast ht gas ut f the Galaxy! Sme will rain back dwn and mix int the galaxy HST Artist's cnceptin/cmputer simulatins Super-bubbles in Large Magellanic Clud (LMC) (nearby galaxy) All spiral galaxies are cnstantly changing Cycle f starà gas The Star-Gasà star Star Cycle Ingredients f Interstellar Medium (ISM) (stuff between the stars) Very cld gas: star birth Mre stuff in ISM inventry Cl gas: neutral H Ht H Really ht gas Dust Nw let us lk at them in turn. 6