PPT-Disk Galaxies – Including the Milky Way.

M51 A typical spiraldisk galaxy The M81 group of galaxies M82 M81 Satellite galaxy Satellite galaxy M81 group showing hydrogen emission at radio wavelengths Composite image of M 81 Blue shows XRay observationshigh energy pink infrared dust. (Resolved by Galileo). Milky Way:. Galactic Structure and Dynamics. Milky Way has spiral structure. . Galactic Bulge surrounds the Center. . Powerful radio source Sagittarius A at Center. C. ontains Super-Massive Black Hole . The Milky Way Galaxy. When you look into the hazy band of light across the sky, you are actually looking at our galaxy from the inside. While an awesome sight, you can only truly begin to see it if you get away from city lights on a moonless night. . Recap. Canvas homework: due on Wednesday. Lab this week: Galaxy Morphology. Campus Observatory. Milky Way galaxy. Stars: . brightnesses. , masses, sizes, compositions, evolution. Interstellar matter: gas, dust. Galaxy. part 2. Unit: . Galaxies. Star systems like our Milky Way. Contain a few thousand to tens of billions of stars.. Large variety of shapes and sizes. Galaxy Diversity. The Hubble Deep Field:. Q: in order to study the spatial distribution of the thin disk (which dominates the Milky Way luminosity) surface photometry in the K band from space has been used. What is the advantage of the K band? What sort of stars give off most of their light at 2 microns. . Loners. Interactions were once . believed to be unimportant . and rare.. Galaxies were thought to . be . isolated loners. , well . separated from one . another . a. nd scarcely interacting.. Au Contraire!. Spiral Structure. . The Astronomical Context. By the 1920’s, we knew that the once-mysterious spiral nebulae were flattened galaxies. . Our Milky . Way is . also. flattened. . Two obvious . questions arose:. megaparsecs. away be moving with respect to us, according to Hubble’s Law? Hint: H. 0. = 70 km/s/. Mpc. 1,400 km/s. 14,000 km/s. 140,000 km/s. 140 km/s. How fast would a galaxy 2,000 . megaparsecs. Contains more than 100 billion stars. Is one of the two largest among 40 galaxies in the Local Group. Our Solar System is located a little more than half way from the galactic center to the edge of the galactic disk.. Let’s look back at the rotational velocity equation:. v = (M. interior. G/r). 0.5. The rotational velocity is constant at big r values.. What must we conclude?. The mass interior to the orbit is still increasing. Even after the radius r has gone beyond the last of the stars. It must be increasing in order to hold v constant.. Galaxies (part I) . T. Howard. The Galaxy – part I -- Overview. New distance unit: the . parsec. (pc).. Using Earth-orbit parallax, if a star has a . parallactic. angle of 1",. it is 1 pc away. . Here’s the mystery story we’ll unfold…. Fuzzy blobs in the sky – new solar systems, or “galaxies”?. Observational tests. Herschel’s map of the “universe” . (what we today know as just our Galaxy). The astonishing variety of galaxies derived from a few structural types. Sec 1.3. Irregulars. = misfits in any class. Edwin Hubble . The Realm of the Nebulae . (1936. ). ‘. Tuning Fork’ classification scheme of galaxies. Are Nebulae within or outside of our galaxy??. Nebula comes from a Greek word meaning Cloud. April 1920, National Academy of Sciences , Washington, DC. Harlow Shapley (had determined size of Milky Way Galaxy) pushed that nebulae were relatively close by objects..