The Milky Way Our Galactic Home 9B 9B

The Milky Way Our Galactic Home 9B 9B

The Milky Way Our Galactic Home 9B 9B Goals Structure of our Galaxy. Its size and shape.

How do stars and things move through it? Mass and Dark Matter. The Galactic Center. 9B The Milky Way

Stars Dust Gaseous Nebulae Open Clusters Globular Clusters

Pulsars Black Holes How do they all fit together to make our galaxy? 9B Optical emission from stars and nebulae 9B

ar-Infrared stellar emission copyright E. L. Wright and COBE 9B ar-Infrared dust emission copyright E. L. Wright and COBE

9B adio emission from neutral hydrogen copyright J. Dickey 9B -ray emission from hot gas copyright S. Digel and ROSAT

9B mma-ray emission from pulsars and black holes copyright NASA 9B Where are We? We arent at the

center of the Milky Way. Where is the center then? Globular Clusters point the way. M10 copyright Credner and Kohle

9B You Are Here 9B 9B ar-Infrared stellar emission copyright E. L. Wright and COBE

9B Galactic Distances How do we know the distance to stars and clusters in our galaxy? Trigonometric parallax good out to 100 pc. We believe galaxy is ~30 kpc wide. How do we know?

9B Spectroscopic Parallax If you know how luminous a star REALLY is and how bright it looks from Earth, you can determine how far away it must be to look that faint. For any star in the sky, we KNOW: Apparent Magnitude (m) Spectral Type (O, B, A, F, G, K, M) Luminosity Class (Main Sequence, Giant, etc).

These are denoted by a roman numeral (V, III, I, ). Combine spectral type and luminosity class to get absolute magnitude (M). From Lecture 7B: m M give you distance. 9B Example

Deneb is A2Ia star m = 1.25 A2 Blue star Ia Supergiant M = -8.8

distance m M 5log10 10pc Distance = 1000 pc 9B Standard Candles Standard Candles If we know how bright something should

be, and we know how bright it looks Distance Variable stars. RR Lyra stars Cepheid variables 9B Variable Stars For RR Lyrae stars: Average luminosity

is a standard candle Always ~ 100 x Sun For Cepheid variables: Pulsation period is proportional to average luminosity Observe the period find the luminosity

Good to 15 Mpc! 9B 9B Rotation Objects in the disk, rotate in the disk.

Nebulae Open clusters Young stars Objects in the halo, swarm in a halo. Old stars Globular clusters

9B and Formation Picture the formation of the Sun:

Spherical cloud Condenses to disk Planets in a plane Oort cloud sphere. Perhaps the same with the galaxy? 9B Missing Mass

From variable stars we know distances. From Doppler shift we know rotation velocity. Use Keplers Third Law (again) to get mass of the Milky Way. M = 1011 x Msun 2 P a 3

2 4 3 P a GM 2 9B

Dark Matter What causes the mass to keep on increasing? Dont see anything there. Thus dark matter. Brown dwarfs

Planets White dwarfs Strange matter? Use gravitational lensing (last lecture) to look for these dark objects. 9B 9B

The Heart of the Galaxy Because of all the dust in the Galaxy, we cant see its center in visible light. Can use IR and radio to pierce the dust.

9B 200 pc 5 pc Sagittarius A* - Sgr A* 9B Stellar Motion

Infrared images of stars in the Galactic Center over 8 years. The + is the radio source Sgr A* Conclusion: Must be over one million solar masses within less than 1/5 of a light year! Supermassive Black Hole! Event Horizon < 0.05 AU!

Probably in the centers of all spiral galaxies. Copyright Eckart & Genzel 9B

Recently Viewed Presentations

  • Beijing Consensus - Western Washington University

    Beijing Consensus - Western Washington University

    Beijing Consensus From China Daily - Official View China's Alternative Development Model Caution ZHANG, Weiwei (2 November 2006). "The allure of the Chinese model" (PDF). International Herald Tribune. Retrieved 28 January 2014. It is inaccurate to describe the Chinese model...
  • Macro-invertebrates Field Study

    Macro-invertebrates Field Study

    Oceanic zones. What is the difference in life between the photic and aphotic zones? Those other aquatic environments! Salt marshes, Intertidal zone, mangroves and coral reefs! What biotic and abiotic challenges to organisms face when trying to survive?
  • NEOPLASIA - STIKesDHB

    NEOPLASIA - STIKesDHB

    NEOPLASIA Hepar yang mengandung metastasis kanker Perbandingan antara tumor jinak & ganas (contoh: leiomyoma >< leiomyosarcoma) 4. Epidemiology Epidemiologi kanker (study tentang pola kanker pada populasi) dapat memberikan pengetahuan tentang: Penyebab / asal kanker Faktor resiko terjadinya kanker Hubungan antara...
  • International Mindedness

    International Mindedness

    In multi-level classrooms, expose students to vocab . at their level . of development. Students will naturally learn . Tier 1 words first, then Tier 2, then Tier 3. All levels can learn all types of words . simultaneously, but...
  • The Quotation Sandwich

    The Quotation Sandwich

    In- text citations are included after the quotation mark but before the period. According to Professor Katy Smith in her article "English in the Modern World," "English is the hardest language to learn" (22). Notice that the citation is included...
  • Velkommen til gudstjeneste - Flinck Hansen

    Velkommen til gudstjeneste - Flinck Hansen

    Guds Søn kom for at tjene og gav for os sig hen da faldt et frø i jorden til evigt liv igen. 587 - Guds Søn kom for at tjene 1, S* 587 - Guds Søn kom for at tjene...
  • G.R.A.P.E.S. The big ideas of social studies Geography

    G.R.A.P.E.S. The big ideas of social studies Geography

    G.R.A.P.E.S. The big ideas of social studies * * * * * * * * * G Geography How climate and landscape affect lifestyle. Crops (ex: corn, wheat, etc. Natural Resources (ex: diamonds, oil, copper, etc.) Landforms (ex: mountains, desert,...
  • Corporate Insights Seminar - Absa CIB

    Corporate Insights Seminar - Absa CIB

    Apart from being an information source on a cross section of trends for many journalists, he currently writes columns for City Press, SAA'sSawubona magazine, Acumen (a C-suite business quarterly for GIBS) and has a monthly radio slot on MetroFM, as...